Vitamins

Achieving a balanced and varied diet is usually adequate to provide us with sufficient nutrients to maintain general health and well being, and will contain enough essential nutrients i.e. vitamins,minerals,amino acids and essential fatty acids as well as carbohydrates and fats for energy. However, weight-loss pure vegetarian, macrobiotic, and several other diets can place some people at risk of deficiencies that vary with the type of diet.

Whilst there is standard guidance on the amounts of vitamins that should be consumed provided in the Recommended Daily Allowances or RDA, nutritional requirements will vary between individuals and depend on their time of life i.e. infancy, childhood, pregnancy, adulthood, old age - as well as the effects of genetics and lifestyle.

Certain groups of people have been found to be at especially high risk of dietary deficiencies.

Elderly - Studies have found that elderly people living in their own homes, often have dietary deficiencies of vitamin A and vitamin E, and occasionally of vitamin D, vitamin B1, and vitamin B2.

Pre-menopausal women have been found often to consume low amounts of, vitamin A, and vitamin C.

The recommended daily allowance of vitamins and minerals is as follows the values given by the European union are substantially the same as those of

Vitamin Deficiencies

Vitamin A

Dietary deficiency of vitamin A is uncommon in healthy people except in older age groups. Vitamin A is important for the function of the immune system, and is essential for normal growth and development. Deficiency leads to poor vision in dim light and eventually to blindness.

Beta-carotene

Beta-carotene is a precursor to vitamin A, but may have a separate role in human health. Controlled research has shown that beta-carotene supplements can increase the numbers of some white blood cells and enhance immune functions in healthy people, although other trials found no positive or negative effect of synthetic beta-carotene on the risk of many other diseases, including several types of cancer, hear disease, diabetes, age-related eye disease, or intermittent claudication.

Thiamin (Vitamin B1)

Thiamin is needed to release energy from carbohydrate. The amount required is related to the amount of carbohydrate eaten. Deficiency of thiamin causes beri-beri, a disorder of the nervous system, which occurs in communities where polished rice is the main food eaten. A different type of thiamin deficiency affecting brain function is sometimes seen in alcoholics. Thiamin is found in whole grains, nuts and meat, especially pork. In the UK, white and brown flour and many breakfast cereals are fortified, which means deficiency is rare.

Riboflavin (Vitamin B2)

Riboflavin is required to release energy from protein, carbohydrate and fat. Although there is no specific deficiency disease, low intakes lead to dryness and cracking of the skin around the mouth and nose. Excess riboflavin is excreted in the urine.

Niacin

Deficiency results in a disease called pellagra, but deficiencies in the western diet are very rare.

Vitamin B6

Vitamin B6 (pyridoxine) is involved in the metabolism of protein. Deficiency may occur as a complication of disease and drug effects, where absorption of vitamin B6 may be affected. Vitamin B6 is also known to be involved in the regulation of homocysteine levels in the blood - elevated homocysteine levels are associated with several diseases, including heart disease, stroke, Alzheimer's disease, and osteoporosis, though it is unknown whether homocysteine has a direct role in causing these diseases.

Vitamin B6 is found in a variety of foods: beef, fish and poultry are rich sources.

Vitamin B12

Vitamin B12 (cyanocobalamin) is used in the formation of blood cells and nerve sheaths. Dietary deficiency is rare, although it is sometimes seen in vegans who obtain virtually no vitamin B12 in their diet unless it is supplemented, as normal dietary intake is exclusively from animal sources. Deficiency is also caused by a lack of intrinsic factor - the substance needed for the absorption of vitamin B12. This leads to a type of anaemia in which red cells are enlarged and also to neurological damage. Many foods have added B vitamins, which ensures adequate supplies.

Certain medications however can cause Vitamin B12 deficiency, for example people who take acid-blocking drugs for long periods of time. Although vitamin B12 deficiency in the elderly is often due to age-related declines in absorption of vitamin B12 from food, vitamin B12 supplements can be absorbed sufficiently in members of this age group if they do not have pernicious anaemia or other significant gastrointestinal disorders.

Folate

Where deficiencies occur, they will usually be due to poor diet or an increased requirement, eg in pregnancy, from drug nteraction and due to mal-absorption.

The requirement for folate doubles during pregnancy, and insufficient intake of folic acid has been linked with low birth weight and an increased incidence of neural tube defects in newborns.

Vitamin C

Vitamin C, sometimes called Ascorbic acid is a water soluble vitamin required for the production of collagen - the protein in connective tissue. Vitamin C also helps the body absorb iron from plant sources, and severe deficiency leads to scurvy. This disease is characterised by bleeding gums, poor wound healing and damage to bone and other tissues. It is rarely seen in Britain today, although it may occur very occasionally in older adults.

If the body is under stress, ascorbic acid is used up more quickly. Smoking is one such stress, and smokers should ensure they eat foods and drinks containing vitamin C.

Vitamin C is found almost exclusively in plant foods, and is particularly abundant in fresh fruit and vegetables. Supplementation with over 200 mg per day of vitamin C by healthy people does not result in higher vitamin C concentrations in the body, and may be no more helpful for preventing disease than smaller amounts.

Vitamin D

In its active form, Vitamin D works as a hormone in controlling the amount of calcium absorbed by the intestine. Vitamin D is also essential for proper bone mineralisation.

Vitamin D can be obtained either from the diet or from sunlight exposure. However, these sources can be insufficient, especially in the older population, in vegans, and during the winter months. Six to fourteen percent of healthy adult Western European populations have been reported to be vitamin D deficient. In the UK some groups of people (eg older Asian adults, Asian women and Asian children) are at risk of vitamin D deficiency because of poor diet or inadequate exposure to sun.

Deficiency of vitamin D leads to skeletal deformity in children (rickets) and to pain and muscle weakness in adults (osteomalacia). Vitamin D insufficiency is associated with bone loss and fractures in older people, and supplementation with vitamin D has been shown to reduce bone loss in some, but not all, studies.