alpha (alpha)-tocopherol

alpha (α)-tocopherol

the most biologically active form of vitamin E, which is the most important antioxidant in cell membranes. Its principal function is to stabilize the structural integrity of membranes by breaking the chain reaction of lipid peroxidation. Vitamin E is also essential for normal function of the immune system. See also reactive oxygen species, vitamins; Table 1.
Table 1: Micronutrients: vitamins
VitaminRNI (DoH 1991)SourcesAction/functionsDeficiencyExcessSpecial points
Water soluble
Vitamin B group
B1 Thiamin(e)0.4 mg/1000 kcalFortified breakfast cereals, yeast extract, vegetables, fruit, wholegrain cereals, milk, liver, eggs, porkCoenzyme for carbohydrate metabolismEncephalopathy can occur with alcohol excess and low food intake. Beri-beri where polished rice is stapleHeadache, insomnia, irritability, contact dermatitisRequirement related to carbohydrate intake
B2 Riboflavin
  • Female 1.1 mg/d
  • Male 1.3 mg/d
Milk, milk products, offal, yeast extract, fortified breakfast cerealsCoenzyme for the metabolism of carbohydrate, fat and proteinFissures at corners of mouth; tongue inflammation; corneal vascularizationNo toxic effects, since large quantities are not absorbedDestroyed by sunlight
B3 Niacin (nicotinic acid and nicotinamide)6.6 mg/1000 kcal as nicotinic acid equivalentsMeat, fish, yeast extract, pulses, wholegrains, fortified breakfast cerealsEnergy metabolism, as part of coenzymes NAD and NADP involved in oxidation and reduction reactionsPellagra: dermatitis, diarrhoea and dementiaLiver damage, skin irritationAlso synthesized from the amino acid tryptophan
B5 Pantothenic acidNone setWidespread in food, e.g. liver, eggs, yeast, vegetables, pulses, cerealsProtein, fat, carbohydrate and alcohol metabolismVomiting, insomniaNot reported
B6 Pyridoxine
  • Female 1.2 mg/d
  • Male 1.4 mg/d
Meat, fish, eggs, some vegetables, wholegrainsProduction of haemoglobin and of coenzymes involved in many metabolic processesRare. Metabolic and nervous system disordersPeripheral nerve damageRequirement is related to protein intake
BiotinNone setWidely distributed in many foods, e.g. offal, egg yolk, legumes, etc. Can be synthesized by intestinal bacteriaEssential in fat metabolismRare; dermatitis, hair loss, nausea, fatigue and anorexiaNone known
B12 Cobalamins15 μg/g of proteinAnimal products, meat, eggs, fish, dairy products, yeast extract
  • Essential for red blood cell formation and nerve myelination.
  • Needed for use of folate
Anaemia; irreversible spinal cord damageNot reported
  • Absorption requires 'intrinsic factor' produced by the stomach.
  • Only in foods of animal origin, so strict vegetarians and vegans require supplements
Folates (folic acid)200 μg/dGreen leaf vegetables, bread, fortified breakfast cereals, yeast extract, liverRed blood cell production; DNA synthesis
  • Anaemia; growth retardation. May contribute to Alzheimer's.
  • Fetal defects
Can mask the effects of B12 deficiencySupplements before and during pregnancy reduce the incidence of spinal cord defects
Vitamin C ascorbic acid40 mg/d
  • Citrus fruits, kiwi fruit, blackcurrants, strawberries; green peppers, green leaf vegetables, potatoes, tomatoes.
  • Content decreases with storage
Collagen synthesis, formation of bones, connective tissue, teeth. Iron absorption for red blood cell production. Acts as an antioxidantSore mouth and gums; capillary bleeding; scurvy; delayed wound healing, scar break downDiarrhoea; oxalate stones in kidneysDestroyed by cooking in the presence of air and by plant enzymes released when cutting and grating raw food
Fat soluble
Vitamin A retinol
  • Female 600 μg/d
  • Male 700 μg/d
As retinol in liver, kidney, oily fish, egg yolk, full-fat dairy produce. As the provitamin carotenes in green, yellow, orange and red fruit and vegetables, e.g. broccoli, carrots, apricots, mangoes, sweet potatoes and tomatoesVisual pigments in retina, aids night vision. Normal growth and development of tissues; essential for healthy skin and mucosae. Acts as an antioxidantPoor growth; rough dry skin and mucosae; xerophthalmia and eventual blindness; increased risk of infection; poor night visionIn pregnancy, high doses can cause fetal malformationsSynthesized in the body from carotenes present in the diet
Vitamin D cholecalciferol ergosterol10 μg/d if houseboundOily fish, egg yolk, butter, fortified margarine; action of ultraviolet rays (sunlight)Calcium and phosphorus homeostasisRickets (children); osteomalacia (adults)Rare; weight loss and diarrhoeaProduced in the body by action of sunlight on a provitamin in the skin: deficiency develops in those who are not exposed to sun
Vitamin E tocopherols tocotrienesNone setWheat germ, vegetable oils, nuts, seeds, egg yolk, cereals, dark green vegetables
  • Antioxidant.
  • Protects against cell membrane damage
Neurological abnormalities; anaemia: rare, from malnutrition or malabsorptionMuscle weakness, gastrointestinal disordersRequirement is increased with increased intake of polyunsaturated fatty acids
Vitamin K phylloquinones menaquinonesNone setGreen leafy vegetables, fruit and dairy productsNeeded for the production of prothrombin and other coagulation factorsImpaired clotting; liver damageNot so far observed from naturally occurring vitaminSynthesized by intestinal bacteria so deficiency unusual
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