Biotin is a water-soluble vitamin and a member of the vitamin B complex.
Biotin was formerly known as vitamin H or coenzyme R.
In the UK, the average dietary intake in adult women is 28µg daily and in adult men is 39µg daily. Biotin is also produced by colonic bacteria, but the effect of this on biotin requirements is not known.
Biotin functions as an integral part of the enzymes that transport carboxyl units and ﬁx carbon dioxide. Biotin enzymes are important in carbohydrate and lipid metabolism, and are involved in gluconeogenesis, fatty acid synthesis, propionate metabolism and the catabolism of amino acids.
Biotin is ubiquitous in the diet. The richest sources of biotin are liver, kidney, eggs, soya beans and peanuts. Meat, wholegrain cereals, wholemealbread,milkandcheesearealsogood sources. Green vegetables contain very little biotin.
Biotin is absorbed rapidly from the gastrointestinal tract by facilitated transport (at low concentrations) and by passive diffusion (at high concentrations). Absorption is greater in the jejunum than the ileum and minimal in the colon.
Biotin is bound to plasma proteins.
Excess biotin is excreted largely unchanged in the urine. It also appears in breast milk.
Biotin deﬁciency is a risk only in those patients on prolonged parenteral nutrition (who will automatically be given multivitamin supplements). Deﬁciency has been induced by the ingestion of large amounts of raw egg white, which contain the biotin-binding protein, avidin, to a diet low in biotin. Marginal biotin deﬁciency may also occur in pregnancy.
Symptoms of biotin deﬁciency include anorexia, nausea, vomiting, dry scaly dermatitis, glossitis, loss of taste, somnolence, panic and an increase in serum cholesterol and bile pigments.
Biotin has been claimed to be of value in the treatment of brittle ﬁnger nails, acne, seborrhoeic dermatitis, hair fragility and alopecia, but such claims need further conﬁrmation by controlled clinical trials.
A trial of biotin (2.5mg four times daily) in women with brittle nails found a 25% increase innail thickness,as assessed by electron microscopy.
Biotin deﬁciency has been associated with sudden infant death syndrome (SIDS). In one study, the median biotin levels in the livers of infants who died from SIDS were signiﬁcantly lower than those of infants who died from explicable causes. However,evidence that biotin deﬁciency is an important contributory factor in SIDS is circumstantial and there is no unequivocal proof. There is no requirement for biotin supplements in newborn or young infants. Supplements should not be sold to parents for this purpose.
Precautions/contraindications No problems have been reported.
Pregnancy and breast-feeding No problems have been reported.
Adverse effects None reported.
Drugs Anticonvulsants (carbamazepine, phenobarbitone, phenytoin and primidone): requirements for biotin may be increased.
Biotin is available in the form of tablets and capsules. However, it is available mainly in multivitamin preparations.
The dose is not established. Dietary supplements provide 100–300µg daily.
Upper safety levels
The UK Expert Group on Vitamins and Minerals (EVM) has identiﬁed a likely safe total daily intake of biotin from supplements alone of 970µg.
(excerpted from) Dietary Supplements, Third Edition, by Pamela Mason, BSc, MSc, PhD, MRPharmS, published by Pharmaceutical Press, London, 2007.