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Vitamins

Unlike fat carbohydrate and protein, vitamins and minerals are needed only in very small amounts. Most vitamins and minerals cannot be made by the body and so must be provided by the diet. Vitamin D however, can be made by the action of sunlight on the skin, and small amounts of niacin (B vitamin) can be made from the amino acid tryptophan. Deficiency diseases can result if insufficient amounts of vitamins or minerals are available to the body either through insufficient levels in the diet or through malabsorption.

Vitamins act as co-factors in enzyme activity, some are antioxidants (prevent oxygen from doing damage to the body) and one, vitamin D, is a pro-hormone.

There are two groups of vitamins:

• Fat soluble (vitamins A, D, E and K)
• Water soluble (all the others)

How much of each vitamin and mineral do we need?
The body requires different amounts of each vitamin and mineral because each has a different function. Individual requirements also vary depending on age, gender, level of activity and state of health. The Department of Health has drawn up Dietary Reference Values for vitamins and minerals for different groups of healthy people.

Fat Soluble Vitamins:

1. Vitamin A (retinol)
2. Vitamin D (cholecalciferol)
3. Vitamin E (tocopherols)
4. Vitamin K

5. Vitamin C
6. Vitamin B1
7. Vitamin B2 (riboflavin)
8. Niacin
9. Vitamin B6 (pyroxidine)
10. Vitamin B12 (cyanocobalamin)
11. Folate

Vitamin A (retinol):

Found as retinol in foods from animal sources and as carotenoids in plant foods e.g. 11? carotene. Excess retinol can be toxic particularly to the unborn child.

Sources: liver, whole milk, fatty fish, cheese, butter, carrots, dark green leafy vegetables and orange coloured fruits.

Vitamin D (cholecalciferol):

Found as cholecalciferol and ergocalciferol. It is converted in the liver to a hormone which controls calcium absorption in the intestine. Most important source is the action of UV light on skin, where those who are house?bound are at particular risk of Vitamin D deficiency, as are some Asian women due to their traditional dress and custom.

Sources: sunlight, margarine, oily fish, egg yolk and fortified breakfast cereal.

Vitamin E (tocopherols).

Is an antioxidant and prevents oxidation of lipids in cell membranes. Can reduce risks of some types of cancers and heart disease.

Source: vegetable oils, nuts, vegetables, cereals.

Vitamin K

Essential for the clotting of blood.

Source: made by bacteria in gut of humans, and is found in foods of animal origin and dark green leafy vegetables.

Vitamin C (ascorbic acid)

Required for the production of collagen, the protein in connective tissue. Helps body to absorb iron from plant sources. May play a protective role against some cancers.

Source: fresh fruits, especially citrus fruits, fruit juices, green vegetables, potatoes.

Vitamin B1(thiamin) Needed to release energy from carbohydrates.

Source: whole grains, nuts, meat, fortified bread and breakfast cereals.

Vitamin B2 (riboflavin) Needed to release energy from protein, carbohydrate and fat. Source: cereals, nuts, pulses, green vegetables, fruit, fortified cereals.

Niacin

Can lower blood lipid levels and in addition to dietary sources can be made by the body from the amino acid tryptophan.

Source: In addition to dietary sources can be made by the body from the amino acid tryptophan. Also found in liver, beef, pork, mutton and fish, fortified breakfast cereals.

Vitamin 136 (pyroxidine)

Involved in the metabolism of protein. Deficiency can occur as a result of disease and drug effects.

Source: beef, fish and poultry.

Vitamin B12 (cyanocobalamin)

Used in the formation of blood cells and nerve sheaths. Deficiency can occur in vegans since animal products are the only natural dietary source of this vitamin.

Source: beef, eggs, milk, fortified breakfast cereals.

Folate:

Involved in the formation of red blood cells. Deficiency can be due to poor diet or an increased requirement e.g. during pregnancy, through drug interaction and malabsorption. Higher intake of folic acid or foods rich in Folate, before conception and during the first 12 weeks of pregnancy reduce the incidence of neural tube defects in babies e.g. spina bifida.

Sources: dietary sources include liver, orange juice, dark green vegetables, nuts, wholemeal bread and fortified breakfast cereals.

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