Vitamins are organic compounds that mainly function in enzyme systems to enhance the metabolism of proteins, carbohydrates, and fats. Without these substances, the breakdown and assimilation of foods could not occur. Certain vitamins participate in the formation of blood cells, hormones, nervous system chemicals, and genetic materials.

Vitamins are classified into two groups, the fat-soluble and the water-soluble vitamins. Fat-soluble vitamins include vitamins A, D, E, and K. The water-soluble vitamins include vitamin C and the B-vitamin complex.

Fat-soluble vitamins are usually absorbed with foods that contain fat. They are broken down by bile and distributed through the arteries. Excess amounts are stored in the body's fat and in the liver and kidneys. Because fat-soluble vitamins can be stored, they do not have to be consumed every day.

Vitamin A consists of a group of compounds, including retinol, that are important for good vision and healthy skin. Vitamin A also promotes growth and supports the immune system. Insufficient dietary intake of vitamin A can cause vision problems and increased susceptibility to infection. Very high intakes can cause headaches, hair loss, and liver damage. Sources of vitamin A include fish-liver oils, milk, eggs, carrots, and spinach. Carotene, which is present in green and yellow fruits and vegetables, is converted to vitamin A in the body.

Vitamin D acts much like a hormone and regulates calcium and phosphorus absorption and metabolism. Humans get most of their vitamin D from exposure of the skin to sunlight. A deficiency leads to rickets in children or osteomalacia in adults.

Vitamin E is a chemical compound found primarily in plants. Its main function is to protect cell membranes from oxidation. Insufficient dietary intake can result in weakened red blood cells and neurological dysfunction, causing loss of muscle coordination and vision problems. The richest sources of vitamin E include vegetable oils and the products made from them, such as margarine. Other sources include wheat germ and nuts.

Vitamin K is necessary for the coagulation of blood. It assists in forming the enzyme which is needed to produce fibrin for blood clots. Vitamin K is produced in sufficient quantities in the intestine by bacteria, but is also provided by leafy green vegetables such as spinach and kale, egg yolk, and many other foods.

The water-soluble vitamins, C and B complex, cannot be stored and therefore need to be consumed daily to replenish the body's needs.

Vitamin C (ascorbic acid) is a water-soluble vitamin, and its main source is citrus fruits. It is needed to form collagen, a fibrous substance that connects tissue. Vitamin C helps wounds heal and keeps bones and teeth strong. Insufficient dietary intake of vitamin C can cause scurvy. Sources of vitamin C include citrus fruits, broccoli, spinach, tomatoes, and potatoes.

The most important B-complex vitamins are thiamine (B1), riboflavin (B2), nicotinic acid or niacin (B3), pyridoxine (B6), pantothenic acid, lecithin, choline, inositol, para-aminobenzoic acid (PABA), folic acid, and cyanocobalamin (B12). These vitamins serve a wide range of important metabolic functions and prevent such afflictions as beriberi and pellagra.

Folate (folic acid) helps the body create new cells by aiding in the production of nucleic acids, which are essential to all living cells. Insufficient dietary intake of folate can cause anemia and limit the body's ability to create new tissue. Folate is found in many foods. Particularly rich sources include liver, yeast, leafy vegetables, and legumes (such as beans).

Niacin (vitamin B3) is essential for cell metabolism and helps maintain the nervous and digestive systems and skin health. Meat, eggs, milk, and whole-grain enriched breads and cereals contain niacin.

Biotin is a memeber of the B-complex, sometimes known as vitamin H: it functions as a co-enzyme in a wide variety of body actions, including energy production and maintaining healthy skin, hair, nerves and bone marrow. Deficiency can occur as a result of antibiotic use: the best sources are dried brewer's yeast and yeast extract

Riboflavin (vitamin B2) helps the body maintain mucous membranes and derive energy from protein and carbohydrates. Insufficient dietary intake can cause cracked skin around the mouth and skin rashes. Meat, fish, milk products, and green vegetables (such as broccoli and asparagus) are good sources of riboflavin.

Thiamine (vitamin B1) helps the body derive energy from carbohydrates and helps regulate the nervous system. Sources of thiamine include cereal grains, brewer's yeast, liver, kidney, and legumes (such as beans).

Vitamin B12 (cobalamin) helps the body create new cells, maintain nerve cells, and use certain fats and amino acids (the building blocks of protein). Insufficient dietary intake can cause anemia and the breakdown of certain nerves. The main food sources of vitamin B12 come from animals, including meat, fish, and milk products.

Vitamin B6 helps the body break down and use amino acids (the building blocks of protein) and contributes to the general functioning of cells. Insufficient dietary intake of vitamin B6 over a long period of time may cause convulsions, anemia, and irritation of the skin. Large doses taken over a long period of time may cause nerve damage. Dietary sources rich in vitamin B6 include chicken, fish, liver, pork, and whole grains.

Inorganic mineral nutrients are required in the structural composition of body tissues; they also participate in such processes as the action of enzyme systems, the contraction of muscles, nerve reactions, and the clotting of blood. These mineral nutrients, all of which must be supplied in the diet, are of two classes: the major elements such as calcium, phosphorus, magnesium, iron, iodine, and potassium; and trace elements such as copper, cobalt, manganese, fluorine, and zinc.

Calcium is the body's most abundant mineral. It is essential for developing and maintaining bone strength. It also aids nerve conduction, muscle contraction, and blood clotting. Insufficient dietary intake of calcium can lead to stunted bone growth in children and osteoporosis (loss of bone mass) in adults. Excessive intake can cause constipation and limit absorption of other minerals. Sources of calcium include milk products and dark-green leafy vegetables (such as broccoli).

Phosphorus contributes to the strength of bones and teeth. It also is important in many of the body's chemical reactions, such as the transfer of energy. Phosphorus deficiency is extremely rare because most foods contain the mineral. Excessive dietary intake of phosphorus can reduce levels of calcium in the body. Sources rich in phosphorus include meat, milk products, and cereal grains.

Magnesium is a mineral found in very small amounts in the body. It is essential for bone growth, the formation of protein, and the maintenance of muscle and nerve cells. Insufficient dietary intake of magnesium over a long period of time may cause nausea, muscle weakness, and mental confusion. Most foods contain magnesium. Rich sources include nuts, whole grains, green vegetables, and legumes (such as beans).

Sodium, with the element chlorine, makes up table salt. Sodium helps maintain the balance of fluid outside the cells of the body. It also aids in nerve conduction and muscle contraction. Excessive intake of sodium can cause edema (swelling of body tissue) and hypertension.

Iron is essential for the body to generate energy. Iron is a component of hemoglobin, a protein in the blood that carries oxygen throughout the body. Iron deficiency causes anemia, with symptoms that include fatigue, weakness, and difficulty in concentration. Iron can reach toxic levels in the body when ingested in extremely large doses. Sources of iron include meat, fish, eggs, and legumes (such as beans).

Iodine is needed to synthesize hormones of the thyroid gland. A deficiency leads to goiter, a swelling of this gland in the lower neck. It is estimated that worldwide more than 150 million people suffer from iodine deficiency diseases.

TRACE ELEMENTS are other inorganic substances that appear in the body in minute amounts and are essential for good health. Little is known about how they function, and most knowledge about them comes from how their absence, especially in animals, affects health. Trace elements appear in sufficient amounts in most foods.

Copper is among the more important trace elements: it is present in many enzymes and in copper-containing proteins found in the blood, brain, and liver. Copper deficiency is associated with the failure to use iron in the formation of hemoglobin.

Zinc helps form enzymes, a type of protein. Enzymes help chemical reactions - such as the healing of wounds - occur at a proper rate. Insufficient dietary intake of zinc causes a variety of health problems, including stunted growth, slow wound healing, and failure of the immune system. Excessive intake can cause anemia, vomiting, and immune-system failure. Meat, liver, eggs, and seafood are good sources of zinc.

Manganese is an essential trace element for human beings: an adult's body contains between 10 and 20mg. It functions to assist growth and maintain a healthy nervous system, as well as being a co-fctor for many enzymes and vitamins. Deficiency can result from poor dietary intake, particularly from high consumption of processed foods: best dietary sources are cereals, wholemeal bread, nuts, pulse and fruit.

Molybdenum is an essential trace element for animals and man: adult body content is 9mg, with most in the liver. It functions in the iron metabolism and helps prevention of tooth decay. Deficiency is associated with high intakes of refine dand processed foods: best food sources are buckwheat, beans, wheatgerm and liver.

Fluorine, which is retained especially in the teeth and bones, has been found necessary for growth in animals. Fluorides, a category of fluorine compounds, are important for protecting against demineralization of bone.

Potassium helps maintain the balance of fluid within the cells of the body. It also aids nerve conduction and helps maintain normal blood pressure. Potassium is found in all foods, particularly fruits, vegetables, and fresh meat.

Other trace elements include chromium and selenium.

BIOFLAVONOIDS (vitamin P): are complex compounds which enhance the effectiveness of vitamin C: together they strengthen capillaries; anti-viral/anti-inflammatory properties help protect from free radicals. EG: quercetin (found in onion & garlic) inhibits growth of cancer cells. Found in fruit, vegetables, nuts, seeds, leaves and flowers.