why you need vitamins in your body

Why you need vitamins in your body

Introduction.

 A general description of vitamins is in the main text. Vitamins are divided into those that are fat-soluble and those that are water-soluble. Fat-soluble vitamins are A, D, E and K; the water-soluble ones, B group and C. The water-soluble vitamin B group is complex. Although often found together in similar types of food – cereals, milk, liver, etc. – they are not related chemically. These vitamins are all coenzymes – organic (non-protein) com- pounds which, when the appropriate ENZYME is present, have an essential function in the chemical reaction catalysed by the enzyme. The vitamin B group comprises B1 (thiamine, aneurine), B2 (riboflavin), B3 (niacin, nicotinic acid), B6 (pyridoxine), B12 (cobalamin, cyanocobalamin), biotin, folacin (folic acid) and pantothenic acid. Unlike fat-soluble vitamins, the water- soluble ones are not stored in large amounts in the body so deficiency of these is more likely.

Fat-soluble vitamins

VITAMIN A

 (Preformed specific compounds: RETINOL, retinal, RETINOIC ACID. Precursor: CAROTENE)

 Functions_____ Maintenance of epithelial cells and mucous membranes. Constituent of visual purple (for night vision). Necessary for normal growth, development and reproduction. Maintenance of immune system. Symptoms of deficiency Keratinised skin, dry mucous membranes, xerophthalmia. Night blindness. Susceptibility to disease. Symptoms of toxicity Dry skin. Loss of appetite and hair, enlarged spleen and liver, abnormal pigmentation of skin. Fetal malformations.

 Food sources__ Preformed vitamin A Liver, especially cod and halibut liver oil; egg yolk; milk and butter. Carotene Dark-green, leafy vegetables, especially spinach, broccoli, kale. Deep orange vegetables and fruits, especially carrots, tomatoes, apricots.

 Recommended daily amounts (IUs*)___ Babies and children 1,875–3,500 Boys (>11 years) and men 5,000 Girls (>11 years) and women 4,000 Lactating women 6,000–6,500 *International Units

VITAMIN D

 (ERGOCALCIFEROL or CALCIFEROL [vitamin D2]; cholecalciferol [vitamin D3]; 25- hydroxycholecalciferol [main circulating form of vitamin D]; 1,25-dihydroxy-cholecalciferol [main active form of vitamin D]; precursor of vitamin D2: ergosterol [plants]; of vitamin D3: 7-dehydrocholesterol [in skin])

 Functions____ Helps in absorption of calcium and phosphorus. Regulates blood concentrations of calcium. Promotes mineralisation of teeth and bones. Symptoms of deficiency Rickets in children. Osteomalacia in adults. Symptoms of toxicity Calcification of soft tis- sues, hypercalcaemia, renal stones, loss of weight and appetite, nausea and fatigue, failure of growth.

Sources____ Cod and halibut liver oils, bony fish, egg yolk, fortified milk, butter and poly- unsaturated margarine. Sunlight acts on ergosterol in plants to produce vitamin D2 and on the skin to produce vitamin D3.

Recommended daily amounts (IUs)___ Babies and children 300–400 Subjects aged11–25 400 Subjects over 25 200 Pregnant and lactating women 400

VITAMIN E

Functions___ Prevents oxidation of vitamin A in gut. Protects red blood cells from haemolysis. Maintains cell membranes by reducing the oxidation of polyunsaturated fats. Symptoms of deficiency Breakdown of red blood cells. Symptoms of toxicity Headache, nausea, longer blood-clotting times.

Food sources___ Wheat germ, vegetable oils, legumes, nuts, whole grains, fish, green, leafy vegetables.

Recommended daily allowances (mg)___ Babies and children 3–7 Boys (>11 years) and men 10 Girls (>11 years) and non-pregnant women 8 Pregnant and lactating women 10–12

VITAMIN K

 (PHYTOMENADIONE, phylloquinone)

Functions__ Necessary for the formation of pro- thrombin and other factors necessary for blood clotting. Symptoms of deficiency Haemorrhage. Symptoms of toxicity Haemolytic anaemia, liver damage. Sources Dark-green leafy vegetables, especially alfalfa, spinach, cabbage. Cauliflower. Egg yolk. Soybean oil. From synthesis by intestinal bacteria.

Recommended daily amounts (µg)____ Babies and children 5–20 Boys (>11 years) and men 45–80 (increasing with age) Girls (>11 years) and women 45–65 (increasing with age) Pregnant and lactating women 65

CHOLINE The basic compound participates in the synthesis of LECITHIN and other phospho- lipids as well as of acetylcholine. Choline, which helps to transport fat in the body, and is essential to life, is sometimes classed as a vita- min, but the body is able to produce the compound.