Epidemiological research is the study of disease trend among populations. It can involve comparison between inhabitants of different countries, or of those living in the same country, state and city. Such populations based research can be useful in identifying potentially fruitful leads for further research. (Biss et al, 1971)

The masai people are a war-like tribe residing in East Africa who for the last 10,000 years have existed as cattle herding nomads. Their sustenance is derived from large amount of high fat milk and meat which may be supplemented by fresh cattle blood in the dry season.

Thanks to their copious consumption of high fat animal food, the masai males ingests a hefty 300g of mostly saturated fat on a daily basis. If lipid hypothesis had any merit, the masai resident should be riddled with obesity and coronary heart disease (Biss et al. 1971).

The residents of Pukapuka and Tokeluau, two tiny pacific atolls, were also examined in 1960’s. Due to their daily consumption of coconut, the Pukapuka and Tokeluau obtained 35%-53% of their calories from fat respectively. Only a few grams of their daily fat intake were in the form of unsaturated fat, the rest were saturated. Despite their high consumption of saturated fat, residents of both island enjoyed a complete absence of chronic heart disease and a remarkable low incidence of other degenerative diseases (Prior et al, 1981).

The more fashionable current dietary theories is that of the “Mediterranean diet” which attributes the low rate of coronary heart disease (CHD) in southern Europe to the frequent intake of olive oil, fruits, vegetable, legumes and a supposedly low level of saturated fat consumption (FAO Data, 1961- 1999). There is no arguing the benefits of fruits and vegetables. France enjoys the lowest incidence of coronary heart disease in south Europe while enjoying the highest saturated fat intake (FAO data, 1961-1999). Red wine intake has been posited as an explanation for this alleged “paradox” but does not satisfactorily explain the difference. After all, the per capita wine consumption of the Italian, fond of their “Vino rosso” is virtually identical to that of the French yet they suffer from a notably higher rate of coronary heart disease CHD) (FAO data, 1961-1999).


The bioavailability of food consumed is an important issue in nutrition. Nutrition is the relationship of food to the health of the human body (Whitney et al, 1993, Trayor, 1996). The food we consume should provide our bodies with the nutrients (carbohydrate, protein, lipids, minerals, vitamin and water) necessary for good health (Whitney et al. 1993, Trayor 1996).

            Bioavailability is the technical term used to convey the fact that you do not absorb 100% of all nutrients consumed, no matter what form the nutrient is taken (Brooner, 1993). A number of factors affects bioavailability of nutrients.

1)        Factors contained on the food itself.

2)        Factors of human physiology

3)        Factors specific to your health status.

4)        Factors related to the food processing.

5)        Presence of anti-nutritional factors (Dreosti 1993).


Nutrition is the provision to the cells and organisms the materials necessary (inform of food) to support life. (Ezeilo, 2002). The purpose of good nutrition is to provide energy, promote growth and repair of tissues and to regulate various process in the body. The essential nutrients comes from carbohydrate, lipids, protein, minerals, vitamins and water (Ezeilo, 2002).


There are 6 major classes of nutrients; carbohydrate, fats, proteins, minerals, vitamins and water. These nutrient classes can be categorized as either macro nutrients and micro-nutrients. The macro nutrients provides structural materials (amino acids from which proteins are built and lipids from which cell membranes and some signaling molecules are built) and energy (Shils et al. 2005). Some structural materials can be used to generate energy internally, and in either case it is measured in joules or kilo calories (Shils et al. 2005).

            Carbohydrate and protein provides 17kJ approximately (4Kcal) of energy per gram (Shils et al. 2005); though the net energy depend on such factors as absorption and digestive effort (Shils et al; 2005).


Sugar and starch are important carbohydrate in our diet. Starch is abundant in yam, cassava, potatoes, bread, maize, rice and other cereals. Sugar appear in our diet mainly as sucrose (table sugar) which is added to drinks and many prepared foods such as biscuits and cakes ( Ramlingam, 2001).

            Although all foods provide us with energy, carbohydrates are the cheapest and most readily available source of energy. They contain the elements carbons hydrogen and oxygen (eg. Glucose C6H12O6). When carbohydrates are oxidized to provide energy by respiration, they are broken down to carbon dioxide and water. One gram of carbohydrate can provide an average of 16KJ of energy (Ramlingam, 2001 and Shils et al 2005).

            Excess carbohydrate in the body is converted to glycogen or fats in the liver, the glucose is stored in the liver and muscles while the fat is stored as fat depots around the kidney or under the skin (Ramlingam, 2001).

Carbohydrates are of 3 classes

1)        Monosaccharide

2)        Diasaccharides

3)        Polysaccharides

Monosaccharide are the building blocks for all carbohydrate and are of two types, the 6 carbon type (Hexose) namely glucose, fructose and galactose and the 5 carbon chain type (Pentose) namely ribose and xylose. Diasaccharides found in food are sucrose, lactose and maltose. Polysaccharides found in food include starch and fibre (Ezeilo, 2002).


Quantitatively, most dietary carbohydrates come from plants, and about 50% are starches. Some monosaccharide are derived from the digestion of milk (eg galactose) or the metabolism of glucose (eg Ribose) in the body. The glycogen in meat (liver and muscle) is converted into lactic acid during slaughter of the animal. The common source and functions of the various carbohydrates are given in the table below (Ezeilo, 2002)

Common source of Dietary carbohydrates.

Monosaccharide   Glucose

Fruits, vegetable and honey


Fruits and honey


Digestion of milk lactose

Disaccharides       Lactose



Germinating seeds.


Sugar cane, pineapple, carrot

Polysaccharides    fibre      soluble

Fruits, legumes and grains


Vegetable, wheat and bran.

(Ezeilo, 2002)


1)        Source of Energy: Carbohydrate in the form of sugar or starch supply energy to non-photosynthetic organism.

2)        Storage of Energy: Carbohydrates can be stored in the form of starch and glucose in plants and animals respectively.

3)        Structural Component: Carbohydrate Polymers serve as structural elements in cell walls of bacteria, connective tissues and cell coats of animals.

4)        Lubrication: Carbohydrates Lubricates skeletal Joints to provide adhesion between cells. Hybrid molecules such as proteoglycans and glycoprotein are components of cell surface and intracellular supportive systems (Diribe et al, 2002).


1)        Sorbitol, a sugar alcohol obtained from glucose produces cataract when it accumulates in the lenses of diabetics.

2)        Mannito, also a sugar alcohol is used as osmotic diuretic to reduce cerebral edema.

3)        Keratin sulphate when found along with chrondrotin sulphate in the cartilages, the cornea of the eye and pulpy nucleus of the intervertebral disc may result to disease conditions.

4)        Hyaluronate is an effective lubricants and a shock absorber.

5)        Heparin is found in the mast cell and can be used as an anticoagulant to inhibit blood clothing (Diribe et al, 2002).


Proteins are built from amino acids, unlike, carbohydrates and fats which are made up of carbon, hydrogen and oxygen. Amino acids have in addition nitrogen and some of them also contain sulphur (Ezeilo, 2002).

            Proteins when digested provide the chemical substance needed to build cells and tissue e.g. skin, muscle, blood and bones. Neither carbohydrates, nor fats can do this and so it is essential to include some proteins in the diet (Ramlingam, 2001).

The body requires amino acids to produce new proteins (Protein retentions) and to replace damaged proteins (maintenance) as there is no protein or amino acid storage provision, amino acid must be present in the diet. Excess amino acids are discarded, typically in the urine (Ezeilo, 2002).

            Some amino acids are essential (an animal cannot produce them internally) and some are non-essential (the animal body can produce them from either nitrogen-containing compound). About 20 amino acids are found in the human body, and about ten of these are essential and therefore must be included in the diets (Berg et al 2002). A diet that contains adequate amount of amino acids (essential) is particularly important in some situations during early development and maturation, pregnancy, lactation or injury (Berg et al, 2002). Excess amino acids from protein can be converted into glucose and used for fuel, a process called gluconeogenesis. The amino acids remaining after such conversions are discarded (Berg et al, 2002).


A complete protein sources contain all the essential amino acids, an incomplete protein source lacks one or more of the essential amino acids. It is possible to combine two incomplete protein source (eg. Rice and beans) to make a complete protein source and this characteristic combination are the basis of distinct cultural cooking tradition. (Ramlingan, 2001).

            Sources of animal protein include, Meats, fish, egg, diary products such as milk and cheese (Ramlingan, 2001). Plant contains some protein, but groundnuts and beans or cereals like wheat and maize are the best source of plant protein ( Ramlingan, 2001).


1)        Fibrous Protein: Have a relatively simple, regular linear structure. These proteins often serve structural roles in cells. They are insoluble in water or in dilute salt solution ( Garrette et al,  2005).

2)        Globular Protein: Are roughly spherical in shape, their polypeptide chain is completely folded so that the hydrophobic amino acid side chain are in the interior of the molecule and the hydrophilic side chains are on the outside exposed to the solvent, water, Globular protein are soluble in aqueous solution ( Garrette et al, 2005).

3)        Membrane protein: Are found in association with the various membrane systems of cells. Membrane proteins have hydrophobic amino acid chains oriented outwards for interaction with the non-polar phase within the membrane. They are insoluble in aqueous solution but can be soluble in solutions of detergent (Garrette et al. 2005).


1)        Many proteins are enzymes: The largest classes of proteins are enzymes. These enzymes are organic catalysts that speed up the rates of biological reaction. Each enzyme is specific in its function and acts only in a particular reaction. Virtually every step in metabolism is catalyzed by an enzyme (Garrette et al. 2005).

2)        Control of metabolism and Gene expression: A number of proteins do not perform any obvious chemical transformation but nevertheless can regulate the ability of other proteins to carryout their physiological functions such proteins are referred to as regulatory proteins. Hormones are one class of regulatory proteins examples include, insulin, pituitary, somatotropin, thyrotrophic (Garrette et al, 2005).

3)        Transport and storage of molecules: Many small molecules and ions are transported by specific proteins for examples;

a)         Haemoglobin transport oxygen in erythrocytes

b)        Myoglobin (Mb) transport oxygen in muscles.

c)         Transferin carries iron in blood plasma.

d)        Ferritin store iron in the liver (Diribe et al, 2002)

4)        Cordinated Motion: Muscle contraction occurs by the slide motions of two kinds of protein filament called. Myosin and action. On the microscopic shade such coordinated motion as the movement of the chromosome in mitosis and the propulsion of sperm cells by their flagella also are produced by contractile assemblies consisting of proteins ( Diribe et al, 2002).

5)        Mechanical support: some proteins contribute to the mechanical strength of some tissues in the body for example a fibrous protein, collagen is responsible for the high tensile strength of skin and bones in the body. (Diribe et al. 2002).

6)        Immune Protection: some proteins play a vital role in immune response in the body. Antibodies are proteins with high specificity for recognizing and attacking foreign substances in the body called Antigens. Proteins therefore, play the important role of distinguishing between self and nonself in the living states (Diribe et al, 2002).


Animal fats are found in meat, cheese, butter and egg yolk, plants fat occurs as oil in fruits (palm oil) and seeds (sunflower seeds) and are used for cooking and making margarine. Fats contains only carbon, hydrogen and oxygen but in different proportion to the carbohydrate (Ramlingan, 2001).

            A molecule of dietary fats typically consist of several fatty acids (containing long chains of carbon and hydrogen atoms) bonded to a glycerol. They are typically found as triglycerides (3 fatty acids attached to the glycerol backbone) (Ramlingan, 2001).

Fats may be classified as saturated or unsaturated depending on the structure of the fatty acids involved. Saturated fats have all the carbon atoms in their fatty acid chains bonded to hydrogen atoms, where as unsaturated fat have some of these carbon atoms double bonded, so their molecules have relatively fewer hydrogen atoms than a saturated fatty acids of the same length. (Ezeilo, 2002). Unsaturated fatty acids are further classified as monounsaturated (one double bond) or poly unsaturated (many double bond) (Ezeilo, 2002).

            Furthermore, depending on the location of the double bonding on the fatty acid chain, unsaturated fatty acids are classified as omega-3 or Omega-6 fatty acids. 1 gram of fats can provide on average 9kcal of energy (Ezeilo, 2002 and Ramlingan, 2001).


Animal fats are found in meat, milk, cheese, butter and egg yolk. Plant fats occur as oils in fruits (palm oil) and seed (Sunflower seed). Rich Source of cholesterol are egg yolk, meat and liver (Ezeilo, 2002).


1)        Energy Storage: Triglycerides are an efficient form of energy storage that can be mobilized when fuel is needed.

2)        Transmission of information in cells (Signal transduction): Lipid hormones, like steroids and eicosanoids also mediate communication before the cells

3)        Cellular Metabolism: the fat soluble vitamins, A,D E and K are required for metabolism, usually as coenzymes.

4)        Structuring cell membranes: The cell membrane constitutes a barrier for the cell and control the flow of material in and out of the cell (Diribe et al, 2000).

By admin

Leave a Reply

Your email address will not be published. Required fields are marked *