Vitamins

A vitamin is an organic compound required as a nutrient in snuill amounts by an organism. Vitamins regulate chemical reactions I which the body converts food into energy and living tissues. They ulsn are essential nutrients for the healthy maintenance of the cells, tissues, and organs that make up a multicellular organism.

Vitamins are classified as either water-soluble or fat-soluble. In humans there are 13 vitamins: 4 fat-soluble (A, D. E, and K) and water-soluble (8 В vitamins and vitamin C). Water-soluble vitamin dissolve easily in water and are readily excreted from the body with tlx urine. Because they are not readily stored, consistent daily intake in important. Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids and are more likely to accumulate in tin body.

Vitamin A (retinol) is necessary for healthy skin, development ol the bones, and good vision. Sources of this vitamin include cod livei oil, yellow, orange and green vegetables, and milk.

Vitamin B₆ also called thiamine, is necessary for changing starches and sugars into energy. Tt is found in meat and whole-grain cereals, rice Vitamin B₂ or riboflavin is essential for complicated chemical reactions that take place during the body's use of food. Milk, cheese, fish, liver, meat, eggs and green vegetables supply vitamin B_r

Vitamin B, is better known as niacin or vitamin PP. Cells need niacin in order to release energy from carbohydrates. Liver, yeast, lean meat, fish, nuts, and legumes contain niacin.

Vitamins B₅ (pantothenic acid), B₆ (pyridoxine) and B₇ (biotin) all play a role in chemical reactions in the body. Many foods contain small amounts of these vitamins, but mainly meat, dairy products, eggs and whole-grain cereals.

Vitamins B₁₂ or cobalamin and B, (also called folate, folic acid or folacin) are both needed for forming red blood cells and for a healthy nervous system. Vitamin Bp is found in animal products, especially liver. Folate is present in green leafy vegetables.

Vitamin С or ascorbic acid is necessary for the maintenance of the ligaments, tendons, and other supportive tissue. It is considered to be the main immune vitamin. It is found in fruits, especially in kiwifruits, oranges and lemons.

Vitamin D or calciferol is necessary for the body's use of calcium. It is present in cod liver oil and vitamin D-fortified milk.

Vitamin E or tocopherol helps maintain cell membranes. It is one of the known antioxidants. Unrefined vegetable oils, especially wheat germ oil, and whole-grain cereals are especially rich in this vitamin. It is also found in small amounts in most meats, fruits, and vegetables.

Vitamin К (К, — phylloquinone and Kj— menaquinone) is necessary for proper clotting of the blood. Green leafy vegetables contain vitamin K.

Hence, for the most part, vitamins are obtained with food, but a few are obtained by other means. For example, microorganisms in the intestine — commonly known as 'gut flora' — produce vitamins К and B₇ (biotin), while one form of vitamin D is synthesized in the skin with the help of the natural ultraviolet waves of sunlight.

Deficiencies of vitamins are classified as either primary or secondary. A primary deficiency occurs when an organism does not get enough of the vitamin in its food. A secondary deficiency may be due to an underlying disorder that prevents or limits the absorption or use of the vitamin, due to a 'lifestyle factor', such as smoking, excessive alcohol consumption, or the use of medications that interfere with the absorption or use of the vitamin. People who eat a varied diet are unlikely to develop a severe primary vitamin deficiency. In contrast, restrictive diets have the potential to cause prolonged vitamin deficiency, which may result in often painful and potentially deadly diseases, such as scurvy (vit С deficit), rickets (vit D), anaemia (vit B₆) and others.

Avitaminosis is any disease caused by chronic or long-term vitamin deficiency or caused by a defect in metabolic conversion, such as tryptophan to niacin. Conversely hypervitaminosis is the syndrome caused by over-retention of fat-soluble vitamins in the body.