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BIOTIN:
Physiology
and Clinical Effects
Biotin, a water-soluble B vitamin, acts as a coenzyme during the
metabolism of protein, fats, and carbohydrates.
Food
Sources
Good dietary sources of biotin include organ meats, oatmeal, egg yolk,
soy, mushrooms, bananas, peanuts, and brewers yeast. Bacteria in the
intestine produce significant amounts of biotin, which is probably
available for absorption and use by the body.
Deficiency
Risk and Symptoms
Certain rare inborn diseases can leave people with depletion of biotin due
to the inability to metabolize the vitamin normally. A dietary deficiency
of biotin, however, is quite uncommon, even in those consuming a diet low
in this B vitamin. Nonetheless, if someone eats large quantities of raw
egg whites, a biotin deficiency can develop, because a protein in the raw
egg white inhibits the absorption of biotin. Cooked eggs do not present
this problem. Long-term antibiotic use can interfere with biotin
production in the intestine and increase the risk of deficiency symptoms,
such as dermatitis, depression, hair loss, anemia, and nausea. Long-term
use of anti-seizure medications may also lead to biotin deficiency.1
Alcoholics, people with inflammatory bowel disease, and those with
diseases of the stomach have been reported to show evidence of poor biotin
status; however, the usefulness of biotin supplementation for these
individuals remains unclear.2 In animals, biotin deficiency can
cause birth defects.
Recommended
Dosage
The ideal intake of biotin is unknown; however, the amount of biotin found
in most diets, combined with intestinal production, appears to be adequate
for preventing deficiency symptoms. Researchers have estimated that 30 mcg
per day appears to be an adequate intake for adults.3
Typically, consumption from a Western diet has been estimated to be
3070 mcg per day. Larger amounts of biotin (816 mg per day) may be
supportive for diabetics by lowering blood glucose levels and preventing
diabetic neuropathy.4 5 Biotin in the amount of 2.5
mg per day strengthened the fingernails of two-thirds of the individuals
with brittle nails, according to one clinical trial.6
Contraindications
Excess intake of biotin is excreted in the urine; no toxicity symptoms
have been reported.
Biotin works
with some other B vitamins, such as folic acid, pantothenic acid (also
known as vitamin B5), and vitamin B12; however, no solid evidence
indicates that people supplementing with biotin need to also take these
other vitamins. Symptoms of pantothenic acid or zinc deficiency have been
reported to be lessened with biotin,7 though people with these
deficiencies should supplement with the nutrients they are deficient in.
Researchers have speculated that biotin and alpha lipoic acid may compete
with each other for absorption or uptake into cells; but little is known
about the importance of these interactions in humans.8
References:
1. Said HM,
Redha R, Nylander W. Biotin transport in the human intestine: Inhibition
by anticonvulsant drugs. Am J Clin Nutr 1989;49:12731.
2. Zempleni J, Mock DM. Biotin biochemistry and human requirements. J
Nutr Biochem 1999;10:12838 [review].
3. Zempleni J, Mock DM. Biotin biochemistry and human requirements. J
Nutr Biochem 1999;10:12838 [review].
4. Coggeshall JC et al. Biotin status and plasma glucose in diabetics. Ann
NY Acad Sci 1985;447:389.
5. Koutsikos D, Agroyannis B, Tzanatos-Exarchou H. Biotin for diabetic
peripheral neuropathy. Biomed Pharmacother 1990;44:5114.
6. Hochman LG, Scher RK, Meyerson MS. Brittle nails: Responses to daily
biotin supplementation. Cutis 1993;51(4):3035.
7. Somer E. The Essential Guide to Vitamins and Minerals. New
York:Harper, 1995, 702.
8. Zempleni J, Mock DM. Biotin biochemistry and human requirements. J
Nutr Biochem 1999;10:12838 [review].
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