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) compounds 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. Those eating a normal Western diet are very unlikely to experience any vitamin deficiency. There are special circumstances in which it may occur: these include fully breast-fed babies who may have an inadequate vitamin D intake as might children who are have little exposure to sunlight in the summer, especially if dark-skinned; pregnant women who benefit from additional folic acid; those on a heavily restricted diet for medical reasons or by personal choice; and those who cannot absorb food sufficiently, for example in cystic fibrosis and malabsorption syndromes.
(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 in tropical areas.
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, 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 | |
(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 tissues, 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 polyunsaturated margarine. Sunlight acts on ergosterol in plants to produce vitamin D2 and on the skin to produce vitamin D3.
Recommended daily amounts to be taken in autumn and winter or, in children with little exposure to sun, throughout the year, (micrograms)
Babies and children | 8.5–10 (500 mls of formula milk is sufficient to provide this amount, whereas breast milk may be deficient) |
Children and adults | 10 |
Pregnant and lactating women | 400 |
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 (very rare) 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 |
(PHYTOMENADIONE, phylloquinone)
Functions Necessary for the formation of prothrombin 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 (increasing with age) | 45–80 |
Girls (>11 years) and women (increasing with age) | 45–65 |
Pregnant and lactating women | 65 |
The basic compound participates in the synthesis of LECITHIN and other phospholipids as well as of acetylcholine. Choline, which helps to transport fat in the body, and is essential to life, is sometimes classed as a vitamin, but the body is able to produce the compound.
(THIAMINE, ANEURINE)
Functions Has role in carbohydrate metabolism. Helps nervous system, heart and muscles to function properly. Promotes appetite and functioning of digestive tract.
Symptoms of deficiency Polyneuritis, beriberi, fatigue, depression, poor appetite and functioning of digestive tract.
Symptoms of toxicity Anaphylactic shock, lethargy, ataxia, nausea, hypotension.
Sources Whole grains, wheat germ, enriched white-flour products, legumes. Brewer's yeast. Heart, liver, kidney; pork.
Recommended daily amounts (mg)
Babies and children | 0.3–1.0 |
Boys (>11 years) and men | 1.2–1.5 |
Girls (>11 years) and women | 1.0–1.1 |
Pregnant women | 1.5 |
Lactating women | 1.6 |
(RIBOFLAVIN [formerly vitamin G])
Functions Essential for certain enzyme systems important in the metabolism of food (carbohydrate, protein and fat).
Symptoms of deficiency Inflamed tongue, scaling and burning skin, sensitive eyes, angular stomatitis and cheilosis, cataracts.
Symptoms of toxicity None recorded.
Sources Green, leafy vegetables, peanuts, whole grains. Milk and its products, eggs, liver, kidney, heart.
Recommended daily amounts (mg)
Babies and children | 0.4–1.2 |
Boys (>11 years) and men | 1.4–1.8 |
Girls (>11 years) and women | 1.2–1.3 |
Pregnant women | 1.6 |
Lactating women | 1.7–1.8 |
(niacin, NICOTINIC ACID [a derivative of pyridine])
Functions Part of two important enzymes regulating energy metabolism. Promotes good physical and mental health and helps maintain the health of the skin, tongue and digestive system.
Symptoms of deficiency Pellagra, gastrointestinal disturbances, photosensitive dermatitis, depression.
Symptoms of toxicity Flushing, loss of appetite, nausea and vomiting, abnormal energy metabolism, anaphylaxis, circulatory collapse.
Sources Whole grain flour, enriched white flour, legumes. Brewer's yeast. Meat; heart, liver, kidney.
Recommended daily amounts (mg)
Babies and children | 5–13 |
Boys (>11 years) and men | 15–20 |
Girls (>11 years) and women | 13–15 |
Pregnant women | 17 |
Lactating women | 20 |
(PYRIDOXINE [pyridoxal is a coenzyme of pyridoxine])
Functions Important in metabolism of proteins, amino acids, carbohydrate and fat. Essential for growth and health.
Symptoms of deficiency Not fully known but possibly convulsions, peripheral neuropathy, secondary pellagra, depression and oral symptoms.
Symptoms of toxicity Reduces prolactin secretion, which is important for milk production. Damage to sensory nerves. Liver damage.
Sources Whole grains, potatoes, green vegetables, maize. Liver; red meat.
Recommended daily amounts (mg)
Babies and children | 0.3–1.4 |
Boys (>11 years) and men | 1.7–2.0 |
Girls (>11 years) and women | 1.4–1.6 |
Pregnant women | 2.2 |
Lactating women | 2.1 |
(cobalamin, CYANOCOBALAMIN)
Functions Important for haemoglobin synthesis. Essential for normal functioning of all cells, especially of the nervous system, bone marrow, and gastrointestinal tract.
Symptoms of deficiency Pernicious anaemia, subacute degeneration of the spinal cordSymptoms of toxicity Not known.
Sources Not found in significant amounts in plant foods. Eggs, dry milk and milk products. Meat; liver, kidney, heart.
Recommended daily amounts (μg)
Babies and children | 0.3–1.4 |
Subjects over 11 years | 2.0 |
Pregnant women | 2.2 |
Lactating women | 2.6 |
(folate, FOLIC ACID)
Functions Formation of red blood cells. Normal function of gastrointestinal tract. Helps in metabolism of protein.
Symptoms of deficiency Possible neural tube defect in fetuses, anaemia.
Symptoms of toxicity Possible hypersensitivity reactions.
Sources Dark-green, leafy vegetables, legumes, whole grains. Yeast. Kidneys, heart and pancreas.
Recommended daily amounts (μg)
Babies and children | 25–100 |
Boys (>11 years) and men | 150–200 |
Girls (>11 years) and women | 150–180 |
Pregnant women | 400 |
Lactating women | 260–280 |
(BIOTIN)
Functions Takes part in amino-acid and fatty-acid metabolism.
Symptoms of deficiency Rare: dermatitis, soreness of the tongue, dependency.
Symptoms of toxicity Not known.
Sources Egg yolk, cauliflower, kidney, legumes, liver, nuts, yeasts.
Recommended daily amounts 150–300 μg.
(PANTOTHENIC ACID)
Functions An essential component of coenzyme A, which is a key factor in many of the body's metabolic activities.
Symptoms of deficiency Rare, but in a trial on volunteers malaise, abdominal discomfort and sensory disturbances occurred.
Symptoms of toxicity Not known.
Sources Widely distributed in foodstuffs.
Recommended daily amounts Adults probably need about 4 to 7 mg/day.
(ASCORBIC ACID, dehydroascorbic acid)
Functions Protects against infection and helps in wound healing. Important for tooth dentine, bones, cartilage, connective tissue and blood vessels.
Symptoms of deficiency Scurvy, anaemia, swollen and bleeding gums, loose teeth, bruising (from rupture of small blood vessels).
Symptoms of toxicity Kidney stones.
Sources Citrus fruits, tomatoes, strawberries, currants, green, leafy vegetables, broccoli, cabbage, potatoes.
Recommended daily amounts (mg)
Babies and children | 30–45 |
Subjects over 11 years | 50–60 |
Pregnant women | 70 |
Lactating women | 90–95 |