Biotin

Biotin is a water soluble vitamin which was first isolated in 1936. As well as being obtained from dietary sources, biotin is also produced by gut bacteria. Biotin functions as an essential cofactor for several enzymes.

Metabolism

Biotin is essential for carbohydrate metabolism and in the synthesis of fatty acids. It also helps incorporate amino acids into protein.

Genetic material

Biotin is essential for cell growth and replication through its role in the manufacture of DNA and RNA, which make up the genetic material of the cell.  Healthy hair and nails require biotin.

Absorption and metabolism

Biotin is absorbed in the small intestine and any excess is excreted in the urine. Normally, the amount of biotin excreted in the urine and feces is up to six times greater than the amount eaten in food. This is due to the large quantities produced by gut bacteria.

Deficiency

Biotin deficiency is rare due to bacterial synthesis in the gut. Those at risk include infants with inherited deficiency disorders, babies fed biotin-deficient formula diets, those who eat large amounts of raw egg whites which inactivate biotin, and those who are fed intravenously.

Symptoms include hair loss, a scaly red rash around the nose, mouth and other body openings, conjunctivitis, anemia, high cholesterol, loss of appetite, nausea, lethargy, muscle pain, and tingling and numbness in the hands and feet. Mental symptoms include intense depression, sleeplessness and hallucinations. In infants, symptoms include seborrheic dermatitis (cradle cap), developmental delay and a lack of muscle tone. Biotin deficiency also affects the functioning of the immune system. A recent animal study showed a decrease in white blood cell function with biotin deficiency.1

Sources

Liver, kidney, brewer's yeast, egg yolks, whole grains, breads, fish, nuts, beans, meat and dairy products are all good sources of biotin. Food processing techniques can destroy biotin.

Beef liver 100g 100 mcg

Peanuts, roasted 100g 39 mcg

Chocolate 100g 32 mcg

Eggs 100g 25 mcg

Peas, dried 100g 18 mcg

Cauliflower 100g 17 mcg

Mushrooms 100g 16 mcg

Recommended dietary allowances

The adequate intake for biotin has been set at around 30 mcg per day. This increases to 35 mcg per day during breastfeeding. Average daily biotin intake in the American diet is estimated to be around 28 to 42 mcg.

Therapeutic uses of supplements

Large doses of biotin are used to treat infants with a potentially fatal genetic abnormality which leads to an inability to use biotin in the body.

Skin disorders

Biotin supplements are used to treat some skin disorders such as seborrheic dermatitis, which in infants appears to be caused by a biotin deficiency. Supplements are given either directly to the infant or to the mother if she is breastfeeding.

Diabetes

Biotin supplements may help to improve blood glucose control in diabetics by enhancing insulin sensitivity and increasing the activity of enzymes involved in glucose metabolism.2 Biotin in high doses may also be useful in the treatment of diabetic neuropathy. 3

Other uses

Biotin can be used to treat frail, splitting or thin fingernails and to improve hair condition.4 It is also used to treat gray hair, although this is only likely to be useful in cases where there is deficiency. Biotin may improve hair health through its action on the metabolism of scalp oils. Biotin has also been used to treat metabolic abnormalities in sufferers of Duchenne muscular dystrophy,5 to normalize fat metabolism in weight loss programs, and to treat intestinal candidiasis.

Interactions with other nutrients

Biotin works closely with folic acid, pantothenic acid and vitamin B12. It can lessen the symptoms of pantothenic acid and zinc deficiencies. Raw egg white contains a protein called avidin that prevents biotin absorption.

Interactions with drugs

Sulfa drugs, estrogen, and alcohol may raise biotin requirements. Prolonged use of anticonvulsant drugs may lead to biotin deficiency. Long-term use of antibiotics can affect the balance of the digestive system and reduce or stop the manufacture of biotin by bacteria.

1 B墈z-Salda鎙 A; Diaz G; Espinoza B; and Ortega E. Biotin deficiency induces changes in subpopulations of spleen lymphocytes in mice. Am J Clin Nutr 1998;67:431-7

2 Koutsikos D et al. Oral glucose tolerance test after high-dose i.v. biotin administration in normoglucemic hemodialysis patients. Ren Fail, 1996 Jan, 18:1, 131-7

3 Koutsikos D et al. Biotin for diabetic peripheral neuropathy. Biomed Pharmacother. 1990; 44: 511-514

4 Hochman LG et al. Brittle nails: Response to daily biotin supplementation. Cutis. 1993;51: 303-307

5 Honke K; Hasui M; Takano N. Abnormal metabolism of fatty acids and ketone bodies in Duchenne muscular dystrophy, and the effect of biotin on these abnormalities] No To Hattatsu, 1997 Jan, 29:1, 13-8