Function
of biotin in the body
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.
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.
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.
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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.
Supplements
Biotin is available commercially
as isolated biotin or as a complex in brewer's yeast.
Toxic effects of excess
intake
There have been no reported toxic
effects even at large doses.
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. Biotin
in high doses may also be useful in the treatment of diabetic neuropathy.
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Other uses
Biotin can be used to treat frail,
splitting or thin fingernails and to improve hair condition. 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.