DETERMINATION OF HEAVY METALS IN SOME SELECTED FOOD SPICES

TABLE OF CONTENTS

Contents                                                                                                                                  Pages

TITLE PAGE i

CERTIFICATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

TABLE OF CONTENTS v

ABSTRACT viii

CHAPTER ONE 1

1.0 INTRODUCTION 1

1.1 JUSTIFICATION 4

1.2 AIMS 4

1.4 LITERATURE REVIEW 5

1.5 GENERAL BACKGROUND 5

1.6 HISTORY 5

1.7 MINERALS/ HEAVY METALS AND THEIR EFFECTS 7

1.7.1 Copper 11

1.7.1.1 Low Copper/High Copper 11

1.7.2 Manganese 12

1.7.3 Lead 13

1.7.4 Iron 13

1.7.5 Zinc 14

1.7.6 Cadmium 14

1.8 TYPES OF SPICES 14

1.9 USES OF SPICES 15

1.10 IMPORTANCE OF SPICES 15

1.11 SPICES AND THEIR HEALTH EFFECTS 16

1.11.1 Cloves (Sypzygium aromaticum) 16

1.11.2 Garlic (Allium sativum) 17

1.11.3 Nutmeg (Myristica frgrans) 19

1.11.4 Ginger (Zingiber officinale) 20

1.11.5 Negro pepper (Xylopia aethiopica) 21

CHAPTER TWO 22

2.0 MATERIALS AND METHODS 2.1 EXPERIMENTAL MATERIALS 22

2.2.0 METHOD 23

2.2.1 SAMPLES 23

2.2.3.1 DRY ASHING 23

2.2.3.2 WET/ACID DIGESTION 24

2.2.4 THEORY OF ANALYSIS 24

2.2.5 SAMPLE PREPARATION 24

2.2.6 DIGESTION PROCEDURE 25

2.2.7 ATOMIC ABSORPTION SPECTROPHOTOMETRY 25

2.2.7.1 PRINCIPLES OF ATOMIC ABSORPTION SPECTROPHOTOMETRY 25

CHAPTER FOUR 31

4.0 DISCUSSION,CONCLUSIONS AND RECOMMENDATIONS 31

4.1 DISCUSSION 31

4.1.1 Cadmium 31

4.1.2 Copper 32

4.1.3 Iron 33

4.1.4 Manganese 34

4.1.5 Zinc 35

4.1.6 Lead 37

4.2 CONCLUSION 37

4.3 RECOMMENDATIONS 38

REFERENCES 39

ABSTRACT

A spice is a vegetable substance of indigenous or exotic origin which is or has a hot, pigment taste, used to enhance taste of foods or to add to them the stimulant ingredients contained in them. They are sparingly used but frequently used in Kebbi state meals. Six (6) heavy metals were determined in some natural spices in kebbi state, Nigeria. Four of the metals namely zinc (Zn), manganese (Mn), copper (Cu) and iron (Fe) are essential micronutrients and lead (Pb) and cadmium (Cd) are toxic metals. A total ofFive (5) samples  were purchased from  different markets in Kebbi state. The spices were processed into the powdered form and subjected to a wet digestion procedure with a mixture of HNO3. Sample solutions were analyzed for Hg using a Mercury Analyzer Model HG-5000 and for the other metals using AAS spectrophotometer (PG-990) The range of total metals concentration  in (mg/kg) for all the spices from all the markets is 0.0091 to 0.0501 for (Cd). The range for (Fe) is 1.3657 to 4.3453, that for (Mn) is from 0.0154 to 3.0792. (Zn) ranged from 0.0264 to 1.3593, and finally (Cu) is 0.0553 to 0.4491. (Pb) was detected but in a very low amount in all  the samples analyzed.The amount of spice to be consumed in order to exceed the recommended daily intakes for the metals were calculated based on the recommended daily intake for the various metals. The amounts obtained were not unlikely to be consumed considering how sparingly they are used. The results obtained showed that the spices from the various markets in this study are not likely to pose any health risk to the public through consumption of the spices for both the toxic elements and the micronutrients determined.

Correlation analysis showed strong positive and negative correlation between the metals for the spices.

 CHAPTER ONE

1.0 INTRODUCTION

A spice is a vegetable substance of indigenous or exotic origin which is or has a hot, pigment taste, used to enhance taste of foods or to add to them the stimulant ingredients contained in them. It can also be defined as a dried seed, fruit, root, bark or vegetative substance derived from the non-leafy parts of plants. It is used as a food additive for the purpose of flavouring or food flavourings, and sometimes as a preservative by killing or preventing the growth of harmful bacteria (Adamson, 2004).

The use of spices dates back to ancient times. Archaeological excavation has revealed that prehistoric man used the leaves of certain plants to enhance the flavour of the half-cooked foods which he ate (Baillon, 1877).

There are many reasons for which people use spices, though, taste probably tops the list. There are several spices that simply smell good and those smells can be alternately soothing or exciting. Some of the types of spices include Onion, Ginger, Garlic, Cloves, Dawadawa, Cinnamon, Rosemary, Thyme, Marjoram, Pepper, Black Pepper, Olive, Lime, Anise, Nutmeg, Curry, Almond, Turmeric, Oregano, Sage, Lemon balm, Peppermint, Dill, and Coriander. Over the centuries, certain spices have been said to heal every infection, disease and malady known to man. But there is no doubt that spices do have value far beyond enhancing the taste of food.However, besides adding to the taste, spices have multifarious functions that include combating foodborne microorganisms, reducing food poisoning, (Sherman and Billing, 1999) antioxidant function, (Pokorney, 1991) and antimicrobial activity (Shelef, 1983). Spices are also known to possess a wide range of medicinal values. Such values include fight against cancer causing cells, reduction of cholesterol level in the blood and prevention of several skin diseases(Shils, 1999). 

Spices are plants and they grow in the soil. Minerals or elements needed for plants growth are also found in the soil and are used by these plants. Some of these elements or metals are of importance while others are not. Pollution of the general environment has increasingly gathered a global interest since the beginning of this century because it is through this process that some of these dangerous elements or metals get into the plant. In this respect, contamination of agricultural soils and of the environment with heavy metals in the last decades has raised public and scientific interest due to their dangerous effects on human health (Gilbert, 1984). Heavy metals may be present in agricultural soils at low levels but can be accumulated by plant over a period. This has led researchers all over the world to study the pollution with heavy metals of air, water, and foods to avoid their harmful effects (Oehme, 1989; Zakrzewski, 1991; Kennish, 1992) and to determine their suitability for human consumption. People consume spices for several reasons. Some people prefer the processed form which is powdered to the fresh ones. This could be due to storage and convenience. Some surveys conducted have shown that these powdered forms are sometimes adulterated with other substances just to increase the quantity. The presence of some foreign substances such as sand from the environment or method of drying or milling has been reported (FAO/WHO, 2001). These added substances may affect the elemental composition or content by increasing the levels of trace metals if present. Element compositions in a particular plant vary greatly depending upon a number of factors, namely, soil parameters, fertilization management and climate. Also, element compositions vary from section to section within the same plant (Bhattacharjee et al., 1998) but sometimes in the preparation two or more parts of the same plant are combined. Heavy or trace metals play positive and negative roles in human life (Adriano, 1984; Divrikli et al., 2003). Some of the heavy metals such as iron (Fe), manganese (Mn) and copper (Cu) are considered essential but they can become harmful above certain levels. Some metals like cadmium (Cd) and lead (Pb) have toxic roles in biochemical reactions in our body. 

Iron is an integral part of many proteins and enzymes that maintain good health. In humans, iron is an essential component of proteins involved in oxygen transport (Dallman 1986; Institute of Medicine, 2001). It is also essential for the regulation of cell growth and differentiation (Bothwell et al., 1979; Andrews, 1999). A deficiency of iron limits oxygen delivery to cells, resulting in fatigue, poor work performance, and decreased immunity. Iron deficiency anaemia is associated with constipation, nausea, vomiting, and diarrhoea (Bhaskaram, 2001; Haas and Brownlie, 2001; Institute of Medicine, 2001). On the other hand, excess amounts of iron can result in increased risk of free radical damage and cancer and even death (Corbett, 1995). 

Manganese is an extremely important mineral when stabilizing blood sugar. It has strong estrogenic properties, and as a result is the most important element for treating menopausal symptoms, osteoporosis, and postpartum depression. Inadequate manganese intake has been associated with parenteral nutrition, resulting in dermatitis, changes in hair pigmentation and slowed hair growth. Regular dislocation of joints (particularly knee joints) is associated also with insufficient manganese levels. On the other hand, excessive manganese levels increase the risk for tendon / ligament tears and pneumonia. Also loss of sex drive and sperm damage have also been observed in men. Excess manganese interferes with the absorption of dietary iron (Blaurock-Busch, 1997; ATSDR, 2008a). 

Eating food or drinking water with very high cadmium content severely irritates the stomach, leading to vomiting and diarrhoea, hypertension, and sometimes death. Accumulation of lower levels of cadmium over a long period of time can lead to a build-up of cadmium in the kidneys and cause kidney damage (ATSDR, 2008b). 

Copper helps the body to use iron. It is also important for nerve function, bone growth, enhanced body use of sugar and protection of cell membranes from destruction by free radicals. A wide range of cardiovascular and blood disorders may be attributed to copper deficiency. Water that contains higher than normal levels of copper may cause nausea, vomiting, stomach cramps, or diarrhoea (ATSDR, 2004). 

Lead can cause neurological damage in foetus and young children. Lead exposure may also cause weakness in fingers, wrists, or ankles, small increases in blood pressure and anaemia. At high levels of exposure, lead can severely damage the brain and kidneys in adults or children and ultimately cause death; it also causes miscarriage (ATSDR, 2007).

Thus, the benefits of micronutrients may be completely reversed if present at high levels as they may be detrimental to human health. Therefore, the World Health Organisation (WHO) has established levels of metals in foods above which, they should not be consumed. For this reason the levels of trace metals in our food should be of much importance and concern to us. The heavy metal or mineral content of spices is not a well researched area worldwide.

A research conducted in Saudi Arabia on some local spices revealed high levels of some trace metals (Al-Eed et al., 2002). The concentration of lead (Pb) ranged from trace to 14.30 mg/kg on dry weight basis, cadmium (Cd) ranged from 1.25 mg/kg to 3.05 mg/kg, cobalt (Co) from 0 to 0.64 mg/kg and that of selenium (Se) 0 to 13.3 mg/kg. Some of these concentrations are above the limit approved by WHO/FAO and this makes it dangerous due to the health implications associated with them (Gilbert, 1984; Satter et al., 1989). Other countries have also established daily intake for metals. For example the accepted daily intake in Canada for lead is 19.5 µg, for cadmium is 2.4 µg, for iron is 762 µg, for Cobalt is 0.2 µg and for Zinc is 452.1 µg (Meluzzi et al., 1996).

Countries such as Nigeria (Adeyeye et al., 2000), Burkina Faso, Niger (Smith et al, 1996) are but a few in Africa who have done some research. 

1.1 JUSTIFICATION

The justification for this project research is based on the fact that, these food spices are known to possess a wide range of medicinal values to humans upon consumption. Such values includes fighting against cancer causing cells, reduction of cholesterol level in the blood and prevention of several skin diseases (Shils,1999). Also spices served to heal every infection, diseases and malady known to man (Sherman and Billing, 1999). Therefore this project research is carried out to ascertain different levels of some heavy metals in some selected food spices obtained in kebbi state, Nigeria.

1.2 AIMS

The aims of this study is to determine the levels of concentration in µg/g of heavy metals

1.3 OBJECTIVES

The objectives of this study are

To determine the heavy metals concentration in some selected spices obtained in Kebbi State, Nigeria

To find out whether the elements occur in levels within the WHO limit

To determine in any correlation exist between the metals in a spices

 1.4 LITERATURE REVIEW

1.5 GENERAL BACKGROUND

Many people are not particularly interested in agriculture but spices arouse a fascination which goes well beyond their economic importance. This special status which spice plants in general enjoy is even more pronounced in the tropical origin. There is something subconsciously exciting about the flavours and aromas of these foodstuffs. 

A spice is a dried seed, fruit, root, bark or vegetative substance used in nutritionally insignificant quantities as a food additive for the purpose of flavouring, and sometimes as a preservative by killing or preventing the growth of harmful bacteria (Adamson, 2004). Many of these substances are also used for other purposes, such as medicine, religious rituals, cosmetics, perfumery or eating as vegetables. For example, turmeric is also used as a preservative; licorice as a medicine, garlic as a vegetable (Dalby, 2001).

Though the term spice can be used to incorporate herbs, the distinction between herbs and spices can be described as follows, in the kitchen, spices are distinguished from herbs, which are leafy, green plant parts used for flavouring purposes (Bender and Bender, 2005). Herbs, such as basil or oregano, may be used fresh, and are commonly chopped into smaller pieces. Spices, however, are dried and often ground or grated into a powder. Small seeds, such as fennel and mustard seeds, are used both whole and in powder form.

1.6 HISTORY

The use of spices dates back to ancient times. Archaeological excavations have revealed that pre-historical men used the leaves of certain plants to enhance the flavour of the half-cooked food which were eaten. Spices are mention in the Bible with examples being Exodus 35:28, 1 Kings 10:15 etc, the Bible also mentions that in 1000 BC, Queen Sheba visited King Solomon in Jerusalem and offered him "120 measures of gold, many spices, and precious stones." (www.chaddsfordhistory.org).

Ancient Greeks and Romans were familiar with spices and paid high prices for them (Baillon, 1877). Abundant anecdotal information documents the historical use of herbs and spices for their health benefits (Rosengarten, 1969). Early documentation suggests that hunters and gatherers wrapped meat in the leaves of bushes, accidentally discovering that this process enhanced the taste of the meat, as did certain nuts, seeds, berries, and bark. Over the years, spices and herbs were used for medicinal purposes. Spices were also used as a way to mask unpleasant tastes and odours of food, and later, to keep food fresh (www.chaddsfordhistory.org). Ancient civilizations did not distinguish between those spices and herbs used for flavouring from those used for medicinal purposes. When leaves, seeds, roots, or gums had a pleasant taste or agreeable odour, it became in demand and gradually became a norm for that culture as a condiment. Spices were also valuable as items of exchange and trade.

Earlier on, spices were used as a source of trading. During the ancient Roman Empire, trading largely came from Arabia; traders supplied cassia, cinnamon, and other spices and deliberately kept the source of their products secret. The intent was to have a monopoly on the spice trade and the Arabians spun great tales about how they obtained the spices in order to keep their resource value high. They continued to keep the origins secret for several centuries from both Ancient Greek and Ancient Roman civilizations (Rosengarten, 1969; www.chaddsfordhistory.org) until about the 1st century, AD, when the Roman scholar Pliny made the connection between the Arabian stories and the inflation of spices and herbs.

Spices and herbs played an important role in ancient Greek medical science. Hippocrates (460-377 BC) wrote about spices, including saffron, cinnamon, thyme, coriander, mint, and marjoram.Of the 400 herbal remedies utilized by Hippocrates, at least half are in use today (Tapsell et al., 2006). Roughly 500 years later, Theophrastus (372-287 BC), sometimes called the "Father of Botany," wrote two books that summarized the knowledge of over 600 spices and herbs.

Historically, culinary spices and herbs have been used as food preservatives and for their health-enhancing properties. Papyri from Ancient Egypt in1555 BC classified coriander, fennel, juniper, cumin, garlic and thyme as health promoting spices (Tapsell et al., 2006). Records from that time also note that labourers who constructed the Great Pyramid of Cheops consumed onion and garlic as a means to promote health.

As time went on, these foodstuffs became more abundant as crops were extended, first in the country of origin, then in other countries. Prices fell and less wealthy consumers were able to purchase spices, which were gradually becoming less thought of as luxury items. Although spices today are still important in trade, their per capita use for flavouring food has declined in Western civilizations, and certain spices must compete with synthetic flavourings. The demand for spices has remained large in Asia, where spices have a wider social and ceremonial significance than they ever attained in the West. Unlike earlier times when monopolies dominated the spice trade, commerce in spices is now relatively decentralized. Throughout the world, spices and herbs are frequently used in cuisine, largely to improve flavour and to provide new tastes (McCormick.com Spice Encyclopaedia).

Today, people are increasingly interested in enjoying spices and herbs for health benefits. As research is progressing, more evidence is supporting some of the anecdotal information supplied by our ancestors. Thousands of years ago our hunter/gatherer forefathers were forced to adapt to a wide range of climatic and other environmental conditions. Thus, before agrarian societies developed, humans consumed a wide variety of plant species. Some of these plants contained the basic macro and micronutrients needed for survival (carbohydrates, fats, proteins, vitamins and minerals) (Thudichum, 1895). Many of the pungent, stronger-tasting, and richly coloured plants also contained an array of "non-nutritive compounds" that had profound health benefits.

1.7 MINERALS/ HEAVY METALS AND THEIR EFFECTS

Minerals (inorganic nutrients) are materials found in foods that are essential for growth and health and do not contain the element carbon. These include water, sodium, potassium, chloride, calcium, phosphate, sulphate, magnesium, iron, copper, zinc, manganese, iodine, selenium, and molybdenum etc it is made up of both micro and macro nutrients or elements. These micro elements mostly fall under heavy metals. Cobalt is a required mineral for human health, but it is supplied by vitamin B12. There is some evidence that chromium, boron, and other inorganic elements play some part in human nutrition, but the evidence is indirect and not yet convincing. 

Fluoride seems not to be required for human life, but its presence in the diet contributes to long term dental health. Some of the minerals do not occur as single atoms, but occur as molecules. 

These include water, phosphate, sulphate, and selenite (a form of selenium). Sulphate contains an atom of sulphur. We do not need to eat sulphate, since the body can acquire the entire sulphate it needs from protein (Odell and Sunde, 1997).

The statement that various minerals, or inorganic nutrients, are required for life means that their continued supply in the diet is needed for growth, maintenance of body weight in adulthood, and for reproduction. The amount of each mineral that is needed to support growth during infancy and childhood, to maintain body weight and health, and to facilitate pregnancy and lactation, are listed in a table called the Recommended Dietary Allowances (RDA). This table was compiled by the Food and Nutrition Board of the United State of America. All of the values listed in the RDA indicate the daily amounts that are expected to maintain health throughout most of the general population. The actual level of each inorganic nutrient required by any given individual 

is likely to be less than that stated by the RDA. The RDAs are all based on studies that provided the exact, minimal requirement of each mineral needed to maintain health (Institute of Medicine, 1999; 2001).

Table 1.1 Recommended Daily Intake for Food Supplements

 (www.lenntech.com/recommended-daily-intake.htm)

 Minerals

Recommended Daily Intake

Over Dosage

Boron

< 20 mg

Toxic at any more than low level to man

Calcium

1000 mg

Doses larger than 1500 mg may cause stomach problems for sensitive individuals

Chlorine

3400 mg (in chloride form)

Excessive intake as Nacl can lead to health problems in man

Chromium

120 µg

Doses larger than 200µg are toxic and may cause concentration problems and fainting

Cooper

2 mg

As little as 10 mg of copper can have a toxic effect

Fluorine

3.5 mg

No information found

Iodine

150 µg

No information found

Iron

15 mg

Doses larger than 20 mg  may cause stomach upset,constipation and blackened stool

Magnesium

350 mg

Doses larger than 400 mg may cause stomach problems and diarrhea

Manganese

5 mg

Excess manganese may hinder iron adsorption

Molybdenum

75 µg

Doses larger than 200µg may cause kidney problems and copper deficiency

Nickel

< 1 mg

Products containing nickel may cause skin rash in case of allergies

Phosphorus

1000 mg

Contradiction: FAD States that doses larger than 250 mg may cause stomach problems for sensitive individuals

Potassium

3500 mg

Large doses may cause stomach upsets,intestinal problems or heart rhythm disorder

Selenium

35 µg

Doses larger than 200µg can be toxic

Sodium

2400 mg

Excess may cause congestive heart failure

Vanadium

<1,8 mg

Toxic to health of man

Zinc

15 mg

Doses larger than 25 mg may cause anaemia and copper deficiency

Much as we need these minerals for a healthy living, some of these minerals in higher or trace quantities may be damaging to our health. These minerals are called trace or heavy metals.

 Heavy metals are those with atomic weights from 63.546 to 200.590 (Kennish, 1992) and specific gravity higher than 4. Living organisms require trace amounts of some heavy metals, including cobalt, copper, iron, manganese, molybdenum, vanadium, strontium, and zinc, but excessive levels can be detrimental to the organism. These are termed as beneficial heavy metals. These elements, or some form of them, are commonly found naturally in foodstuffs, in fruits and vegetables, and in commercially available multivitamin products (Schrauzer, 1984). Others arefound in the environment such as the soil and water where these plants are grown. Other heavy metals such as mercury, plutonium, and lead are toxic metals that have no known vital or beneficial effect on organisms, and their accumulation over time in the bodies of animals can cause serious illness.

There is a strong link between micronutrient nutrition of plants, animals and humans and the uptake and impact of contaminants in these organisms (De Leonardis et al., 2000; Yuzbasi et al., 2003). The content of essential elements in plants is conditional, the content being affected bythe characteristics of a soil and the ability of plants to selectively accumulate the metals. 

Additional sources of heavy metals in plants are: rainfall, traffic density, use of oil or fossil fuels for heating, atmospheric dusts, plant protection agents, and fertilizers. Certain elements that are normally toxic are, for certain organisms or under certain conditions, beneficial. Examples include vanadium, tungsten, and even cadmium (Lane and Morel, 2000; Lane et al., 2005).

In medical usage, heavy metals are loosely defined and includes all toxic metals irrespective of their atomic weight: "heavy metal poisoning" can possibly include excessive amounts of iron, manganese, aluminium, or beryllium (the fourth lightest element) or such a semimetal as arsenic as well as heavy metals (Duffus, 2002).

Some of these metals are naturally found in the body and are essential to human health. Iron, for example, prevents anaemia, and zinc is a cofactor in over 100 enzyme reactions. High levels of zinc can result in a deficiency of copper, another metal required by the body.

Trace metals therefore, are metals in extremely small quantities, almost at the molecular level, that reside in or are present in animal and plant cells and tissue. They are a necessary part of good nutrition, although they can be toxic if ingested at excess quantities (Underwood, 1977).

Trace metals or micronutrients include iron, magnesium, zinc, copper, chromium, nickel, cobalt, vanadium, molybdenum, and selenium. Trace metals are depleted through the expenditure of energy by a living organism. They are replenished in animals by eating plants, and replenished in plants through the uptake of nutrients from the soil in which the plant grows. Human vitaminpills and plant fertilizers both contain trace metals as additional sources for trace metals (Schrauzer, 1984). 

The elements under this study include, zinc, manganese, iron and copper being micronutrients. 

The rest are mercury, cadmium and lead being the toxic elements. It will therefore be necessaryto know its use or what it does in the human body when spices taken contain them. 

1.7.1 Copper

Copper acts as a catalyst in the formation of haemoglobin, the oxygen-carrying blood component (Lahey, 1975). The areas of highest concentrations in the body tissues are the liver and certain areas of the central nervous system, particularly the brain. Minerals including copper must be bound to a protein to be usable.

Functions of Copper in the body include, helping oxidize glucose and release energy, helping the body absorb iron, aiding the thyroid gland in balancing and secreting hormones, carrying oxygen in the blood stream thus supplying the body's tissues with oxygen. It is also needed for the functioning of the amino acid, tyrosine. It is essential for making red blood cells, necessary for the synthesis of the hormone adrenaline etc. 

1.7.1.1 Low Copper/High Copper

Physical Symptoms of Low Copper include not enough oxygen in the cells, lowered levels of HDL cholesterol, skin problems, swollen ankles, anaemia. Low level causes the cells to suffocate and lack oxygen. It is linked to low enkephalins produced in the brain. Psychological Symptoms of Low Copper include auditory hallucinations, depression. Binge eaters have been found to have lower levels of copper.Copper levels are more often too high than too low. High copper can be toxic. It causeheadaches, hypoglycemia, increased heart rate, nausea, inhibition of urine production, anaemia, hair loss in women, Damage to the kidneys. Copper deposits in the brain and liver causing damage to them (Nolan, 1983). Excessive copper in children is associated with hyperactive behaviour, learning disorders such as dyslexia, and ear infections. High copper interferes with zinc, which is needed to manufacture digestive enzymes. Many high copper people dislike protein and are drawn to high-carbohydrate diets because they have difficulty digesting protein foods (Narang et al., 1991) 

1.7.2 Manganese

Manganese is a trace metal that is present at very low amounts in our body. The human body most likely would contain around 20 milligrams of manganese and most of them will be found and concentrated in the bones, kidneys, liver and pancreas. 

Manganese, which has antioxidant, free-radical-fighting properties, is important for proper food digestion and for normal bone structure. Manganese can help reduce fatigue levels, prevent the incidence and severity of osteoporosis, and even improve memory. Manganese is a trace mineral that helps the body convert protein and fat to energy. It also promotes normal bone growth, helps maintain healthy reproductive, nervous, and immune systems, and is involved in blood sugar regulation. In addition, manganese is involved in blood clotting and the formation of cartilage and lubricating fluid in the joints.

Manganese levels have also been shown to vary with the menstrual or estrus cycle in humans and animals, and low manganese intakes are associated with disruption of reproduction in animals (Penland and Johnson, 1993). Manganese deficiency had been

linked to bone malformation, weakness, seizures, atherosclerosis, confusion, convulsions, eye problems, hearing problems, heart disorders, high cholesterol levels, hypertension, irritability, memory loss, muscle contractions, pancreatic damage, profuse perspiration, rapid pulse, tooth-grinding, tremors, and osteoporosis. Manganese is also linked to decreased superoxide dismutase (SOD) activity in white blood cells, which leaves the body more vulnerable to the damaging effects of free-radicals (ATSDR,2008b).

1.7.3 Lead

Lead accounts for most of the cases of paediatric heavy metal poisoning (Chao and Kikano, 1993). It is a very soft metal and was used in pipes, drains, and soldering materials for many years. Millions of homes built before 1940 still contain lead (e.g., in painted surfaces), leading to chronic exposure from weathering, flaking, chalking, and dust (Myres and Easson, 1992). Every year, industry produces about 2.5 million tons of lead throughout the world. Most of this lead is used for batteries. The remainder is used for cable coverings, plumbing, ammunition, and fuel additives. Other uses are as paint pigments (Myres and Easson, 1992) and in PVC plastics, x-ray shielding, crystal glass production, pencils, and pesticides.

Lead can affect almost every organ and system in your body. The main target for lead toxicity is the nervous system, both in adults and children. Long-term exposure of adults can result in decreased performance in some tests that measure functions of the nervous system. It may also cause weakness in fingers, wrists or ankles. Lead exposure also causes small increases in blood pressure, particularly in middle-aged and older people and can cause anaemia. Exposure to high lead levels can severely damage the brain and kidneys (Loghman-Adham, 1997) in adults or children and ultimately cause death. High-level exposure in men can damage the organs responsible for sperm production (ATSDR, 2000). In pregnant women, high levels of exposure to lead may cause miscarriage (Bellinger et al., 1987).

1.7.4 Iron

Iron is essential for the formation of haemoglobin, the chemical in the blood that carries oxygen to the cells. Low levels of iron cause anaemia (Lahey, 1975). In severe cases, the children become flabby, and they fail to grow normally. Milder cases of iron deficiency may not produce any physical symptoms, but children may learn at a slower pace than children with a proper amount of iron in their diet. The combination of rice, beans, and meat consumed with fresh citrus fruit provides an excellent source of absorbable iron (Gillooly et al., 1983).

Discussion of iron toxicity in this protocol is limited to ingested or environmental exposure. Iron overload disease (haemochromatosis), an inherited disorder, is discussed in a separate protocol. 

Iron is a heavy metal of concern, particularly because ingesting dietary iron supplements may acutely poison young children (e.g., as few as five to nine 30-mg iron tablets for a 30-lb child).

Ingestion accounts for most of the toxic effects of iron because iron is absorbed rapidly in the gastrointestinal tract. The corrosive nature of iron seems to further increase the absorption (Hallberg et al., 1997). Most overdoses appear to be the result of children mistaking red-coated ferrous sulphate tablets or adult multivitamin preparations for candy. Other sources of iron are drinking water, iron pipes, and cookware. Target organs are the liver, cardiovascular system, and kidneys.

1.7.5 Zinc

Zinc is a trace element that is necessary for a healthy immune system. A lack of zinc can make a person more susceptible to disease and illness.Zinc deficiency affects about two billion people in developing world and is associated with many diseases, in children it causes growth retardation, delayed sexual maturation, infection susceptibility and diarrhea, contributing to the death of about 800,000 children word wide per year (Obuobie et al ., 2006).

Zinc is also referred to in nonscientific context as spelter, is a bluish white lustrous, diamagnetic metal, the metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 0 C.

1.7.6 Cadmium

Cadmium is a by-product of the mining and smelting of lead and zinc. It is used in nickel-cadmium batteries, PVC plastics, and paint pigments. It can be found in soils because insecticides, fungicides, sludge, and commercial fertilizers that use cadmium are used in agriculture. Cadmium may be found in reservoirs containing shellfish. Cigarettes also contain cadmium. Lesser-known sources of exposure are dental alloys, electroplating, motor oil, and exhaust. Inhalation accounts for 15-50% of absorption through the respiratory system; 2-7% of ingested cadmium is absorbed in the gastrointestinal system. Target organs are the liver, placenta, kidneys, lungs, brain, and bones (ATSDR,2008a).

1.8 TYPES OF SPICES

There are so many types of spices, some  are very common and some are not. They are Onion, Ginger, Garlic, Cloves, Negro pepper,Dawadawa, Cinnamon, Rosemary, Thyme, Marjoram, Pepper, Black Pepper, Olive, Lime, Nutmeg, Curry, Allspice, Almond, Turmeric, Oregano, Sage, Lemon balm, Peppermint, Dill and Coriander etc. 

1.9 USES OF SPICES

Spices have so many uses. These uses includes: Addition of flavour to foods thus making food taste good, for Medicinal Purposes which includes fighting against cancer causing cells, reducing the cholesterol level in the blood and preventing several skin diseases. Other uses include, Religious rituals, Cosmetics, Perfumery and Aromatherapy. 

1.10 IMPORTANCE OF SPICES

There are many reasons for which people use spices, though, taste probably tops the list. There are several spices that simply smell good and those smells can be alternatetly soothing or exciting. On the other hand, ginger is said to be a stimulant and the smell of ginger could be just what you need to pep up your mood. Over the centuries, certain spices have been said to heal every infections, diseases and malady known to man. But there's no doubt that spices do have value far beyond enhancing the taste of food (Ziegler and Filer, 1996).

Spices play an important role in the nutrition of our daily diet. Scientists have done a lot of research on this and have found out that spices contain more antioxidants than fruits and vegetables. Spices contain more antioxidants when they are dried than when they are raw or fresh. Half teaspoon of spices will contribute more amounts of antioxidants than half a cup of fruits. Spices play an active role by acting as medicines. Cloves, oregano, allspice, cinnamon, sage, peppermint, thyme and lemon balm are some of the spices. These spices may be of a significant dietary source (Pokorney, 1991).

Spices, the predominant flavouring, colouring and aromatic agents in foods and beverages, are now gaining importance for their diversified uses. The nutritional, anti-oxidant, anti-microbial and medicinal properties of spices have far-reaching implications (Shelef, 1983). In the present scenario, the anti-diabetic, anti-hypercholesterolemic, anti-carcinogenic, anti-inflammatory effects of spices have paramount importance, as the key health issues of mankind nowadays are diabetes, cardio-vascular diseases, arthritis and cancer. Spices or their active principles could be used as possible ameliorative or preventive agents for these health disorders (Shils, 1999). 

Extensive studies on animal models carried out indicate that spices could be consumed at higher dietary levels without any adverse effects on growth, organ weights, and food efficiency ratio and blood constituents (Stipanuk, 2000).

However, until recent times, the desiccation and freezing of food was not a viable option for those living in hot, humid climates; these societies discovered chemical preservation, in the form of salt and spices. As the former was only available in certain areas spices were often the only other option to protect food from insect infestation and microbial putrefaction (Sethi and Meena, 1997).

We now know that many of the strongly flavoured phytochemicals which give plants protection against insect and microbial attack are the same compounds that "preserve" our bodies, by protecting us against degenerative disease (Shils, 1999).

Today spices are consumed in much greater quantity and variety in warm, humid countries than in colder climates. India and Thailand have the highest consumption of spices; the warm Mediterranean countries follow somewhat behind these and other Eastern countries but are ahead of the United States. Chilly Scandinavian countries have the lowest spice consumption of all. 

There is the need to consume lots of spices on a daily basis as they can make us feel better, think better, age more slowly, and help to resist the onslaught of scourges like cardiovascular disease, cancer, diabetes, Alzheimer's disease and other chronic degenerative disorders (Shils, 1999).

1.11 SPICES AND THEIR HEALTH EFFECTS

Spices have numerous effects on the human body. Some of the health effects are discussed below. 

1.11.1 Cloves (Sypzygium aromaticum)

Like other spices, cloves are available throughout the year. Cloves are the unopened pink flower buds of the evergreen clove tree. The buds are picked by hand when they are pink and dried until they turn brown in colour. Cloves resemble tiny nails. In fact, it English name is actually derived from the Latin word clavus, which means nail. Although cloves have a very hard exterior, their flesh features an oily compound that is essential to their nutritional and flavour profile. 

Clove contains significant amounts of an active component called eugenol, which has made it the subject of numerous health studies, including studies on the prevention of toxicity from environmental pollutants like carbon tetrachloride, digestive tract cancers, and joint inflammation. In the United States, eugenol extracts from clove have often been used in dentistry in conjunction with root canal therapy, temporary fillings, and general gum pain, since eugenoland other components of clove (including beta-caryophyllene) combine to make clove a mild anaesthetic as well as an anti-bacterial agent (Amaechi et al., 1999). Eugenol, the primary component of clove's volatile oils, functions as an anti-inflammatory substance. Clove also contains a variety of flavonoids, including kaempferol and rhamnetin, which also contribute to clove's anti-inflammatory and antioxidant properties (Friedman et al., 2002).

Like its fellow spices, clove's unique phytonutrient components are accompanied by an incredible variety of traditionally-recognized nutrients. Cloves are excellent source of manganese, a very good source of dietary fibre, vitamin C and omega-3 fatty acids and a good source of calcium and magnesium (Ensminger and Esminger, 1986).

1.11.2 Garlic (Allium sativum)

Garlic is a member of the lily or Allium family, which also includes onions. Garlic is rich in a variety of powerful sulphur-containing compounds including thiosulfinates (of which the best known compound is allicin), sulfoxides (among which the best known compound is alliin), and dithiins (in which the most researched compound is ajoene). While these compounds are responsible for garlic's characteristically pungent odour, they are also the source of many of its health-promoting effects including cancer prevention (Fukushima et al., 1997; Andorfer et al., 2003). In addition, garlic is an excellent source of manganese, a very good source of vitamin B6 and vitamin C and a good source of seleniumNumerous studies have demonstrated potential benefits of regular garlic consumption on blood pressure, platelet aggregation, serum triglyceride level, and cholesterol levels. Routine eating of garlic may also help stimulate the production of nitric oxide in the lining of blood vessel walls, which may help to relax them (Apitz-Castro et al., 1986; Spigelski and Jones, 2001). As a result of these beneficial actions, garlic can be described as a food that may help prevent cancer, atherosclerosis and diabetic heart disease, as well as reducing the risk of heart attack or stroke (Berthold and Sudhop, 1998; Fleischauer et al., 2000). The compounds in garlic responsible for its pungency also excite a neuron pathway providing cardiovascular benefits. Garlic's numerous beneficial cardiovascular effects are due to not only its sulphur compounds, but also to its vitamin C, vitamin B6, selenium, manganese calcium, potassium, iron and copper (Fugh-Berman, 2000; Bautista, et al., 2005). 

One reason for garlic's beneficial effects may be its ability to lessen the amount of free radicals present in the bloodstream (Dillon et al., 2003). According to a study published in Life Sciences, a daily dose of 1 ml/kg body weight of garlic extract for six months resulted in a significant reduction in oxidant (free radical) stress in the blood of patients with atherosclerosis. Garlic is a very good source of vitamin C, the body's primary antioxidant defender in all aqueous (water-soluble) areas, such as the bloodstream, where it protects LDL cholesterol from oxidation. Since it is the oxidized form of LDL cholesterol that initiates damage to blood vessel walls, reducing levels of oxidizing free radicals in the bloodstream can have a profound effect on preventing cardiovascular disease (Superko and Krauss, 2000; Bhattacharya et al., 2004). 

The selenium in garlic not only helps prevent heart disease, but also provides protection against cancer and heavy metal toxicity. A cofactor of glutathione peroxidase (one of the body's most important internally produced antioxidants), selenium also works with vitamin E in a number of vital antioxidant systems (Durak et al., 2004) and another trace mineral, manganese, which also functions as a cofactor in a number of other important antioxidant defence enzymes. Garlic, like onions, contains compounds that fight severe attacks in some cases of asthma and may also help reduce the pain and inflammation of osteoarthritis and rheumatoid arthritis. 

Allicin, is a powerful antibacterial and antiviral agent that joins forces with vitamin C to help kill harmful microbes and lower blood pressure, insulin and triglycerides (Lee et al., 2003). 

Side effects from garlic intake include upset stomach, bloating, bad breath, body odour, and a stinging sensation on the skin from handling too much fresh or dried garlic. Handling garlic may also cause skin lesions. Other, more rare side effects that have been reported by those taking garlic supplements include headache, fatigue, loss of appetite, muscle aches, dizziness described as vertigo (dizziness), and allergies such as an asthmatic reaction or contact dermatitis (skin rash).

1.11.3 Nutmeg (Myristica frgrans)

Unlike other herbs and spices, the health benefits of nutmeg have not been well known, although there are many benefits to this tasty spice. Nutmeg has a variety of health benefits and has been used as a healing herb for many centuries. It can help lower blood pressure and sooth a stomach ache as well as stop diarrhoea and help to detoxify the body. The essential oil, of the nutmeg is particularly effective for soothing many ailments, it is rich in phosphorus, calcium and iron. The most important species commercially known is the Common or Fragrant Nutmeg Myristica fragrans which belongs to the family Myristicaceae.

One of the interesting health benefits of nutmeg oil is its ability to stimulate the brain - it relieves stress and stimulates mental activity. It is even reputed to stimulate dreams. Its ability to improve concentration and increase efficiency was not lost on the ancient Greeks and Romans who used it as a brain tonic despite the fact that it was quite rare and costly.

Nutmeg has anti-inflammatory properties and can be used to treat joint and muscle pain. The oil works particularly well when it is massaged into the affected area (Devereux, 1996). It is an integral spice in Chinese medicine where it is used for stomach pain and inflammation as well as reducing joint swelling. In addition to being an excellent liver tonic which can help remove toxins from the liver, nutmeg oil is also a good herb for the kidney, helping it dissolve kidney stones as well as relieve infections of the kidney. Heart problems may also be somewhat alleviated by nutmeg, as it can help increase blood circulation and stimulate the cardio-vascular system. It is also good for digestion. It can get rid of both gas and stomach aches and can relieve vomiting, diarrhoea, and flatulence as well as encourage appetite. Nutmeg can also help with respiratory problems such as a cough from the common cold. It is an ingredient in cough syrups and is able to relieve asthmatic attack (www.indepthinfo.com). 

While there are many health benefits of nutmeg, it is not advisable to be taken in high doses. It can be toxic and can cause serious problems. Not more than 30 grams (around 6 tablespoons) should be taken in a day, and even this amount may be considered excessive. In low doses, nutmeg produces no noticeable physiological or neurological response. Large doses of 60 g (~12 teaspoons) or more are dangerous, potentially inducing convulsions, palpitations, nausea, eventual dehydration, and generalized body pain (Gable, 2006). 

1.11.4 Ginger (Zingiber officinale)

Ginger is a perennial spice which grows from underground rhizomes, which are often mistakenly called the "roots." Botanically it is the rhizome that provides the slightly hot, citrus-like taste, and wonderful aroma. Its family name is Zingiberaceae.

The rhizome has thick lobes coloured from tan to white. A highly valued variety, especially for medicinal uses, has a blue ring circling the fleshy inside of the rhizome. The nutrients presentinside ginger, especially its volatile oils - gingerols and shogaols, accord a number of health benefits to its users (Chen et al., 2007). In fact, ginger has also been found to be effective in fighting some fatal ailments like cancer (Afshari and Taghizade, 2007). Ginger has been known to contain nutrients such as Calcium, Carbohydrate, Dietary Fibre, Iron, Magnesium, Manganese, Potassium, Protein, Selenium, Sodium, Vitamin C, E and B6. 

Ginger has been found to be helpful in blocking the harmful effects of prostaglandin, a substance that can lead to inflammation of the blood vessels in the brain and even cause migraines. Ginger has been associated with alleviation of the feeling of nausea, even in case of pregnant women (Portnoi et al., 2003). The anti-inflammatory properties of ginger make it effective in alleviation of pains associated with rheumatoid arthritis. Ginger promotes warmth in the upper respiratory tract and thus, is quite effective in treating cold and flu. 

Ginger is quite effective for relief of cramps caused by stomach gas. Ginger makes the platelets less sticky and is thus, pretty helpful in case of circulatory disorders. Preliminary studies suggest that ginger may lower cholesterol and prevents the clotting of blood. Each of these effects may protect the blood vessels from blockage and the damaging effects of blockage such as atherosclerosis, which can lead to a heart attack or stroke. (Bordia et al., 1997). 

There are a variety of uses suggested for ginger. Tea brewed from ginger is a folk

remedy for colds. Ginger ale and ginger beer have been recommended as "stomach settlers" for generations in countries where the beverages are made, and ginger water was commonly used to avoid heat cramps in the US. Ginger has also been historically used to treat inflammation which several scientific studies support, though one arthritis trial showed ginger to be no better than a placebo or ibuprofen. Research on rats suggests that ginger may be useful for treating diabetes (Al-Amin and Zainab, 2006; Thomson et al., 2002). Side effects associated with ginger are rare, but if taken in excessive doses the herb may cause mild heartburn, diarrhoea and irritation of the mouth.

1.11.5 Negro pepper (Xylopia aethiopica)

There are several widely used indigenous forest species which are harvested from the wild. Xylopia aethiopia or Ethiopia pepper or Senegal pepper or locally known as (hwentea), the seeds are used as spice and a substitute for pepper. As a spice Sénégal Pepper should always be used whole and ground, as the hull of the fruit lends the spice its aromatic notes whilst the seeds within lend pungency and bitterness to the flavour. 

The chemical composition and mineral constituents of Senegal pepper, which is valued as a spice in Nigeria, were determined along with the physicochemical characteristics of the seed oil. The seeds had the following chemical compositions: moisture, ash, crude lipid, crude protein crude fibre and carbohydrate. Calcium and potassium were the major minerals in the seed. The exmanagementpid was examined for the fatty acid composition. Linoleic and oleic acids were the predominant unsaturated fatty acids, while palmitic acid was the major saturated acid. The iodine value indicates that the seed oil is a non-drying type. The essential oils of Senegal pepper and four Cameroonian plants used as spices in local food, showed antibacterial and antifungal activity (Tatsadjieu et al., 2003). Seeds are used for stomach-aches, dysentery, bronchitis, cancer, ulcers, fever and debility, rheumatism, post-partum management and fertility-enhancing, and vermifuge (Guardian newspaper, 2009).

CHAPTER TWO

2.0 MATERIALS AND METHODS

2.1 EXPERIMENTAL MATERIALS

The instruments and reagents used in this research project were of analytical grade, these materials include:

 a. Beaker 100cm 3

 b. Conical flask 100cm 3

c. Funnel

d. Crucible

e. Whattman No.1 filter paper

f. Measuring cylinder 50cm 3

g. Weighing balance (DS-75)

h. Distilled water

i. Digestion flask 50cm 3

j. AAS spectrophotometer (PG-990)

k. Nitric acid (HN0 3 )

2.2.0 METHOD

2.2.1 SAMPLES

Some commonly consumed spices were used as samples for the analysis of the heavy metals, they include: Ginger, Garlic, Clove,Nutmeg and Negropepper respectively.

2.2.2 SAMPLE COLLECTION

Five samples each of the 5 spice samples were collected randomly from five different markets in kebbi State.Precautionary measures were taken to avoid any form of contamination. After the collection of samples, Digestion followed.

2.2.3 DIGESTION

Digestion is the process of combusting volatile materials in the sample. The volatile materials are usually organic materials such as carbohydrates, fats and oil, protein and other materials.

After the digestion, it is the inorganic materials usually the trace metal elements that remain. The digestion procedure can be done by two broad methods

(i) Dry  Ashing

(ii) Wet Ashing (Milacic and Kralj, 2003).

2.2.3.1 DRY ASHING

This method involves the complete combustion of all the organic matter only in the raw and processed sample to remain only the non-volatile inorganic mineral element.

The combustion starts by burning the material on the non-luminous part of the Bunsen lame until it stops smoking and then transferred into a muffle furnace which is set between 450° - 550° c (Jarup, 2003).

However precaution must be taken against low result which may be due to any of the following reasons.

a. Volatilization of elements

b. Combination or adsorption of elements with ash constituent or the vessel.

c. Incomplete extraction of the ash, such difficulties can usually be avoided.

2.2.3.2 WET/ACID DIGESTION

All acid procedure makes use of oxidizing agents to break down the organic matters.

The method has some advantages when compared with dry ashing as no volatilization loss occurs. The nutrient elements can be determined in one digest solution, but can not be used for some very hard materials as incomplete digestion may result. Various chemicals such as nitric acid, percholoric and sulphuric acid can be used in the determination of lead, iron, copper, nickel, cadmium and other heavy metals. The use of hydrochloric acid was employed in this project because the digestion is very fast though it is dangerous in the sense that explosion may occur if care is not taken.

The solution after digestion will then be made up to the mark in the volumetric flask to move the sample solution. (Milacic and kralj, 2003).

2.2.4 THEORY OF ANALYSIS

The analysis of trace element present in the sample solution can be carried out by the use of classical or instrumental method.  However the instrumental method of analysis is more reliable than classical method. The instrumental method involves the use of instruments like the flame photometer, Atomic absorption spectrophotometer (AAS) (Agrawal, 2003).

2.2.5 SAMPLE PREPARATION

The spices were collected from five (5) different markets in kebbi state and were brought into the laboratory. The samples were properly washed with de-ionized water; the samples were then ovendried at a temperature of 100°c for between 30 to 60 minutes.Garlic was dried at a temperature of 25°C for 24 hours. They was then ground into the powdered form.

The dried samples were then pounded with the crucible to fine powder, the different samples  were then labeled into different small crucibles for identification

2.2.6 DIGESTION PROCEDURE

The glass wares were washed and cleaned properly and were rinsed with distilled water. Two (2) grams of each sample were weighed into a beaker, 20ml of the acid (Nitric acid)  was added to the sample in the beaker and were stirred continuously for few minutes. Samples were allowed to stand for about 20mins at room temperature to enable the foam that formed to settle.They were then heated in a digestion block on a hot plate for about 20 minutes at a temperature for between 150°c to 250°C.The digested samples were allowed to cool and diluted to 50mL into a volumetric flask and the solution was poured into a labeled sample bottle.

The same procedure was repeated for the rest of the samples and was then taken for analysis of the heavy metals using PG-990 atomic absorption spectrophotometer (Obuobie et al ., 2006).

2.2.7 ATOMIC ABSORPTION SPECTROPHOTOMETRY

2.2.7.1 PRINCIPLES OF ATOMIC ABSORPTION SPECTROPHOTOMETRY

In atomic absorption analysis, the absorption of Light use of an instrument called Atomic absorption spectrophotometer (AAS), in this process, a flame system is generally employed to dissociate elements from their chemical bonds. The atoms absorb light at characteristic wavelength when present in their ground state. A mixture of air and acetylene produce a flame which is of a sufficient high temperature to ensure the presence of free atoms of most elements. The use of nitrous oxide in place of air result in a higher temperature and this is necessary for the estimation of certain elements. (Obuobie et al ., 2006).

CHAPTER THREE

3.0 RESULTS 

 Table 3.1 Concentration of heavy metals in mg/kg in some  selected food spices

Mn mg/kg

Fe mg/kg

Cu mg/kg

Cd mg/kg

Zn mg/kg

Pb mg/kg

WHO Standard

5 mg/kg

300 mg/kg

50 mg/kg

0.3 mg/kg

100 mg/kg

10 mg/kg

Cloves

75.29±2.89

68.27±14.44

8.54±2.47

1.11±0.12

1.44±0.50

-36.62±11.32

Garlic

12.32±2.58

40.81±6.55

7.90±1.02

1.03±0.08

26.18±0.30

-36.93±12.37

Ginger

6.61±1.77

87.04±18.85

5.27±1.86

0.76±0.23

20.76±11.58

-14.86±23.67

Negropepper

3.21±2.53

73.71±5.54

5.24±0.35

0.50±0.28

15.06±9.89

-0.29±0.19

Nutmeg

6.90±1.31

71.35±13.08

2.53±1.58

0.25±0.06

18.32±12.81

-039±0.51

The spices were analysed for six (6) heavy metals. Three of the metals namely manganese (Mn), copper (Cu) and iron (Fe) are essential micronutrients and lead (Pb) and cadmium (Cd)  are toxic metals. A total of six (6) spices were bought from different markets in kebbi state, Nigeria.

3.2 Correlation Analysis

Analysis for correlation between the metals was done using excel. Table 3.3 to 3.7 show the results obtained.

TABLE3.3 CLOVE

Cd mg/kg

Fe mg/kg

Mn mg/kg

Zn mg/kg

Cu mg/kg

Cd mg/kg

1

Fe mg/kg

0.0269

1

Mn mg/kg

0.2945

0.1066

1

Zn mg/kg

-0.5241*

-0.6571*

-0.1053

1

Cu mg/kg

-0.0704*

0.0224

-0.2549

0.1875

1

The values with (*) showed significant correlations.

TABLE 3.4 NUTMEG

Cd mg/kg

Fe mg/kg

Mn mg/kg

Zn mg/kg

Cu mg/kg

Cd mg/kg

1

Fe mg/kg

0.6497*

1

Mn mg/kg

-0.7891*

-0.5751*

1

Zn mg/kg

0.3696

0.3099

0.2281

1

Cu mg/kg

-0.5298*

-0.2354

0.1502

-0.3394

1

TABLE3.5 NEGROPEPPER

Cd mg/kg

Fe mg/kg

Mn mg/kg

Zn mg/kg

Cu mg/kg

Cd mg/kg

1

Fe mg/kg

0.2954

1

Mn mg/kg

0.2553

0.9440*

1

Zn mg/kg

0.6534*

0.7734*

0.7983*

1

Cu mg/kg

0.1003

0.6825*

0.8095*

0.7559*

1

TABLE3.6 GINGER

Cd mg/kg

Fe mg/kg

Mn mg/kg

Zn mg/kg

Cu mg/kg

Cd mg/kg

1

Fe mg/kg

0.0200

1

Mn mg/kg

-0.1932

0.4266

1

Zn mg/kg

-0.1295

-0.1051

0.1115

1

Cu mg/kg

0.4775

0.2280

-0.0033

0.2423

1

TABLE 3.7GARLIC

Cd mg/kg

Fe mg/kg

Mn mg/kg

Zn mg/kg

Cu mg/kg

Cd mg/kg

1

Fe mg/kg

0.6778*

1

Mn mg/kg

0.5702*

0.5511*

1

Zn mg/kg

0.8518*

0.8819*

0.4369

1

Cu mg/kg

0.8386*

0.8889*

0.6815*

0.9037*

1

The values with (*) significant correlations.

For the spices, there was a weak negative correlation between Cd,Fe and Mn in ginger. A weak negative correlation existed between Mn and Fe and Cd, another between Zn and Cd and Fe and another correlation between Cu and Mn all in ginger. All the rest gave a weak positive correlation. 

A strong positive correlation was found between Cd and Zn for clove. All the rest showed weak positive and negative correlations. A strong positive relation existed between Cd and Fe, Mn and Zn in Negropepper. The other metals gave weak positive correlations for Negropepper. 

There was a weak negative and positive correlation between all the metals with the exception of Fe and Mn; Cu and Cd; which showed a strong negative correlation. 

All these were observed for nutmeg.

A weak positive correlation between Cu and Mn was observed for garlic. All the metals showed strong positive correlation among each other.

The strong positive correlations that existed between the metals indicate that, as the concentration of a metal increases, the concentration of the other metal to which it is correlated also increases. A weak positive correlation means that the probability that an increase in the level of one metal causes another to increase is very small. The strong negative correlation means that as the level of one metal increases the level of the other metal decreases. A weak negative correlation means that as the concentration of a metal increases the concentration of the othermetal does not decrease or the decrease is very small.

 For strong positive and negative correlations the values should be 0.5 and above and -0.5 and above respectively

CHAPTER FOUR

4.0 DISCUSSION,CONCLUSIONS AND RECOMMENDATIONS

4.1 DISCUSSION

 World Health Organization (WHO) standards and permissible levels for the selected heavy metals of interest (Iron,Cadmium,Cupper,Manganese,Lead and Zinc) are 15mg/kg, 0.3 mg/kg,50 mg/kg,5 mg/kg,10 mg/kg and 100 mg/kg respectively. The results of this project indicated that the analyzed selected heavy metals; Mn(0.0154 - 3.0792 mg/kg), Cadmium (0.0091 - 0.0501 mg/kg),Zinc (0.0264 - 1.3593 mg/kg),Iron (1.3657 4.3453 mg/kg) and Cupper (0.0553 - 0.4491 mg/kg)  (-0.0040 -  -1.8742 mg/kg) were present in all the samples except for Lead which was detected in very low amount in the spices; the concentrations of heavy metals in spices differ from one sampling location to the other and vary from one specie of spices to the other. Among all the heavy metals analyzed. With the exception of Lead the levels of Manganese,Cadmium,Cupper and Iron detected in most of all the samples analyzed in this research project were lower than the stipulated permissible levels in food by FAO/WHO guidelines.

4.1.1 Cadmium

Of all the toxic metals released in large quantities into the environment cadmium (Cd) generally is regarded as the mostly likely to accumulate in the human food chain (Johannesson, 2002). Cadmium in Clove ranged from 0.0413 to 0.0501 mg/kg. The highest level of Cd recorded in this study was in clove.The levels of Cd obtained for Nutmeg were quite high with the range from 0.0091 to 0.0169 mg/kgThe Cd levels in Negropepper ranged from 0.0131 to 0.0142 mg/kg.

Cadmium levels in Ginger ranged from 0.0205 to 0.0381 mg/kg. The results obtained varied as some markets had low levels while others had levels as high as 0.67 mg/kg.Considering samples from the different markets in Kebbi state it was noticed that the results obtained were varying which suggests that the samples did not come from similar sources. These levels indicate that some amount of Cd were in the soils where the ginger plants were cultivated.

The levels of cadmium obtained in Garlic ranged from 0.0385 to 0.0451 mg/kg. Garlic was relatively rich in Cd concentrations as compared to some of the levels obtained by some of the spices. 

These levels are as a result of the garlic plants being cultivated in soils with some levels of Cd or the garlic plants can accumulate Cd. Taking into consideration the maximum amount obtained in table 3.1, the recommended intake can be exceeded by people who consume large amounts of garlic, but for people who consume small amounts, the recommended intake will not be exceeded.

4.1.2 Copper

The normal levels of Copper (Cu) found in plants have a range 3-40 µg/g (Benton, 1998). Copper levels in clove ranged from 0.2545 to 0.4491 mg/kg. Most of the levels from the various markets were in the range of 0.5721 to 0.8353 mg/kg.Copper levels in Nutmeg from the various markets varied from 0.0553 to to 0.1733 mg/kg. Comparing the levels of Cu in nutmeg to that in clove it was realized that the differences between the levels were small. Ozkutlu et al., (2006) reported the range of copper to be between 3 to 11 mg/kg with the highest level in nutmeg and black pepper. Comparing their values to the values obtained for nutmeg in this study, the values in this study were higher.

The levels of Cu in Negropepper ranged from 0.1970 to 0.2252 mg/kg.

The levels of Cu studied in Ginger varied from 0.1522 to 0.2951 mg/kg.

The levels of Cu in Garlic ranged from 0.2591 to 0.3543 mg/kg.

Ozkutlu et al. (2006) reported the range of copper to be between 3 to 11 mg/kg with the highest level in nutmeg and Cloves.Comparing the values of this study to those obtained by Ozkutlu et al. (2006) it is noticed that, the levels of this study are lower. Nutmeg and Cloves in their study recorded the highest levels. Nutmeg and Negropepper in this study also recorded high levels. They concluded that the levels of copper obtained were far below the recommended levels of intake. A study by Divrikli et al. (2005) recorded values of copper in the range between 3.8 and 35.4 mg/kg which were within the recommended daily intake of Cu of 2mg/day for 70kg body weight (www.lenntech.com). Taking into consideration the maximum intake calculated with the maximum levels presented for this study in table 3.1 above, exposure to Cu through consumption of these spices is not significant. 

Most of the copper levels obtained in this study were low if compared to the normal range of 3-40 mg/kg. Consuming these spices may not pose any health problems as copper is an essential micronutrient which when consumed has some important physiological functions in the body. Copper helps the body to use iron. It is also important for nerve function and bone growth. It also helps the body to use sugar and protect cell membranes form being destroyed by free radicals (ATSDR, 2004).

4.1.3 Iron

Plants requires iron (Fe) for the production of chlorophyll which is needed for manufacture of plants food. It is also needed as a component of many enzymes associated with energy transfer, nitrogen reduction and fixation and liginin formation (www.echochemmicronutrient). The levels of iron in Cloves from the different markets were in the range of 2.0664 to 3.0865 mg/kg.

Levels of iron in Nutmeg varied with a range of 2.2501 to 3.1672 mg/kg. Most of the levels were within the range of 2.3561 to 5.7330 mg/kg with the rest above 10 mg/kg. Considering the levels of Fe obtained though lower than those recorded for clove, the levels are generally high.The levels of Iron in Negropepper ranged from 2.7154 to 3.1572 mg/kg.The levels of Fe obtained for Negropepper were all high and consistent which suggest that plants have the ability to absorb and retain iron.

Iron recorded levels that ranged from 2.9525 to 4.3543 mg/kg in Ginger.

Iron levels in Garlic ranged from 1.3657 to 1.8901 mg/kg.The levels obtained in garlic from the various markets were all within the normal range of plant Fe. 

The results obtained for iron in this study were all high except in two spices. The normal level of Fe in plants ranges from 20 to 300 mg/kg (Benton, 1998) and the levels obtained in this study were all within the normal range. A study by Nnorom et a., (2007) reported results of some of spices recording iron levels as high as 419.05 mg/kg. Plants normally contain high levels of iron and the relatively high levels in this study confirm the results of Onianwa et al., (1999). Levels of iron are expected to be high in plant derived products which was shown by all the samples in this study. The maximum Fe intakes obtained in this study ( table 3.1 above) show that the amounts to be consumed are not likely to exceed the recommended daily intake of 15 mg/day for a 70kg body weight (www.lenntech.com). Thus the exposure to Fe through consumption of these spices is insignificant. Iron is an integral part of many proteins and enzymes that maintain good health. In humans, iron is an essential component of proteins involved in oxygen transport (Dallman 1986; Institute of Medicine, 2001). It is also essential for the regulation of cell growth and differentiation (Bothwell et al., 1979; Andrews, 1999).

4.1.4 Manganese

Manganese (Mn) is an important micronutrient needed by the body for certain processes such as helping to maintain sex hormone production, metabolism of Vitamins B1 and E, activation of various enzymes important for proper digestion to make the body healthy.Manganese in Clove from all the markets was found to have levels ranging from 2.8783 to 3.0792 mg/kg. Considering the highest and the least Mn levels obtained, it was observed that the levels were not high and rather were lower than the results obtained by Ozkutlu et al., (2006) which reported Mn levels within a range of 10 to 355 mg/kg. The highest level was found in clove which is an excellent source of Mn. The clove spice did not record high levels in this study. This could be due to the fact that the soils in which the clove plants were cultivated were not that rich in Mn resulting in low accumulation. The normal range of Mn is 15- 150 mg/kg (Benton, 1998).The levels of manganese in Nutmeg were all low comparing them to that of the other spices. The range is between 0.2380 to 0.3360 mg/kg and above the lowest level of Mn a plant should contain (Benton, 1998).

The manganese in Negropepper ranged from 0.0154 to 0.2105 mg/kg. Comparing Mn from the various markets,though the levels recorded were low they are lower when compared to the range of Mn 15- 150 mg/kg obtained by Benton (1998).

The levels of Mn in Ginger ranged from 0.2102 to 0.3446 mg/kg. The levels recorded for manganese were all below 15 mg/kg.

The manganese levels in Garlic ranged from 0.3736 to 0.5535 mg/kg. The levels recorded by all the markets were all below the range indicating the presence of normal Mn levels in the soil where they were cultivated.

A study by Gupta et al. (2003) on mineral composition of eight common spices reported high levels of Mn in the spices that were studied. The mean levels ranged from 33.6 mg/kg in coriander to107.62 mg/kg in carium. These levels are very high compared to that of this study.Another study by Ozkutlu et al. (2006) on Cd and micronutrient of spices commonly consumed in Turkey showed Mn level with a range of 10 to 355 mg/kg. The highest level was found in clove which seems to be an excellent source of Mn. These levels are very high compared to that obtained in this study. Though the levels of Mn obtained in this study are not very high, the results by Ozkutlu et al. (2006) indicate that plants could accumulate high levels of Mn when it is found in the soil where the plants are cultivated. It can also be low in plants which are naturally rich in Mn but cultivated in soils deficient in Mn.

 It was also reported that these levels obtained were noticeably lower than ones previously found in herbs and spice plants from different parts of the world (Ozkultu et al., 2006). The general levels of Mn obtained by the spices were all below the normal range of 15-150 mg/kg. When the results of this study are compared with the normal range of Mn, the levels were rather low. This could be attributed to the spices being cultivated in soils with some levels of Mn. The recommended daily intake of manganese is 5mg/day for 70kg body weight. Considering the amounts presented in table 3.1 above, exposure to Mn through consumption of these spices is not significant.

4.1.5 Zinc

Zinc (Zn) is an essential element found virtually in every cell of the human body and plays vital roles in the healthy development and growth of the human body. Zinc plays an important role in growth and has recognized action on more than 300 enzymes by participating in their catalytic and regulatory action (Nnorom et al., 2007). The normal levels of zinc range from 15 to 150 mg/kg in most crops and pastures (Benton, 1998). Considering the levels of Zn recorded in Clove which ranged from 0.0264 to 0.0833 mg/kg, the levels can be considered to be low.Levels of zinc in Nutmeg ranged from 0.1415 to 1.0397 mg/kg,  most of the values were within 0.0043 - 1.3593 mg/kg range.Zn levels recorded in Negropepper were low as compared to those obtained in nutmeg and clove. The range is from 0.0311 to 1.0043 mg/kg. All the markets recorded levels below the least normal level plants should have which is 15 mg/kg (Benton, 1998). Divrikli et al. (2005) reported levels of zinc in spices and herbal plants in the range of 5.2-83.7 mg/kg. These levels were high compared to the levels obtained in this study. Some of the levels obtained in this study are within the range of their study indicating that zinc levels vary widely depending on the type of plant and the areas where it was cultivated.

Zn levels in Ginger ranged from 0.4955 to 1.3593 mg/kg. Comparing the general levels of Zn obtained in this study, the levels recorded by ginger are quite high as most were above 0.0264 mg/kg though they were all below the normal range of 15 to 150 mg/kg.

Levels of zinc in Garlic in this study ranged from 1.0339 to 1.0572 mg/kg.

A study by Nnorom et al. (2007) recorded a range of 1.00 to 48.10 mg/kg for zinc. This indicates how low Zn levels can be in plants. They concluded that their results were high. Comparing their levels to that of this study, it can be said that the levels in this study were not high. Another study on micronutrients in spices showed levels of zinc ranging from 4 to 25 mg/kg (Ozkutlu et al., 2006). Their levels were almost in the same range as the levels in this study. They concluded that the levels recorded were within the low range of normal plant zinc. A study by Basgel and Erdemoglu (2005) found that micronutrient concentrations were generally higher in leaves than in the other parts above the ground. The levels of zinc recorded for all the various spices ranged from 0.0264 to 1.3593 mg/kg. The low levels could be attributed to soils in which these spices were cultivated. The low levels could be explained by the fact that zinc is immobile in soil thus making it quite difficult for plants to absorb and transport. It is also not readily translocated within the plant especially in areas where the concentrations are low. Considering the maximum intakes presented in table 3.1. The recommended daily intake of 15mg/day for 70kg body weight (www.lenntech.com) is unlikely to be exceeded.

4.1.6 Lead

 Lead was detected in very low amount (-0.0040 to -1.8742 mg/kg) in all the samples. Gupta et al., (2003) on mineral composition of eight common spices showed that results were heavily scattered because Pb was detected in four out of the spices studied in the range of 1.57-8.69 mg/kg. It was concluded that the contamination might have resulted from some extraneous factors. Al-Eed et al., (2002) reported the range of lead to be from trace to 14.30 mg/kg. They concluded that these levels of lead were dangerous for human consumption. Chizzola et al., (2003) reported that the level of lead were generally low. 

These results indicate that lead can be detected in samples that come from environments that are contaminated with lead and that the levels could be high with serious detrimental effects. It can be low or non detectable in spices that come from soils that are low in lead concentration. 

The spices from this study showed non detectable levels of Pb indicating that, the areas that these spices came from were not contaminated with lead or that the lead in the soil is not in the bioavailable form for plants to absorb. It is gratifying to know that spices from the markets in this study are free from lead contamination and therefore, are safe to consume.

4.2 CONCLUSION

From the analysis carried out, the following conclusions may be deduced from the results obtained. Some metal content in some natural spices found on the kebbi state, Nigeria were determined. The study reports the metal concentration levels in some spices from  Birnin kebbi central market, Jega, Danwarai,Kwanar gari road and Kashin zama markets. All the concentrations of the metals in the spices from the various markets were below the World Health Organization (WHO) limit.

 The concentration of the metals determined in the spices from all the markets considered in milligram/kilogram ranged from 0.0091 to 0.0501 for Cd, 1.3657 to 4.3453 for Fe, 0.0154 to 3.0792 for Mn, 0.0553 to 0.4491 for Cu. Lead was detected but in a very low amount in all  the samples.

 The results obtained showed that the spices from the various markets in this study are not likely to pose any health risk to the public through consumption of the spices for both the toxic elements and the micronutrients determined.

The correlation analysis done for the metals showed that, strong positive and negative correlation existed between the metals for both the markets and the spices.

4.3 RECOMMENDATIONS

The following recommendations are suggested as a result of the outcome of this study

The concentration of heavy metals in other natural food spices in Kebbi State markets which are not covered by this research project should be determined

Spices should be directly sampled from the areas of cultivation

Periodic monitoring of the levels of heavy metals in food spices should be encouraged

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