Biotin is one of eight essential vitamins that comprise the B-complex. It functions as a carrier of carbon dioxide for “carboxylation” reactions. Biotin-requiring carboxylase enzymes catalyze:
- the breakdown of branched chain amino acids and odd-chain fatty acids.
- gluconeogenesis (the production of glucose from non-carbohydrate sources (such as. amino acids)
- the first step in fatty acid synthesis.
Biotin also binds to proteins called “histones,” which are important to the structure of chromosomes. Roles for biotin in gene expression and cellular proliferation have also been postulated.
Due to biotin’s critical role(s), biotin deficiency is potentially quite serious. Deficiency symptoms range from dry skin and brittle hair to nausea, depression and muscular pain. Fortunately, serious deficiencies are relatively rare, since a) biotin is only needed in small amounts; b) the vitamin is present in a wide variety of foods; and c) some biotin is produced by intestinal microflora.
Nonetheless, biotin deficiency can be induced by intravenous feeding; prolonged antibiotic or anticonvulsant therapy and chronic consumption of large amounts of raw egg whites (raw egg white contains avidin, a protein that can bind tightly to biotin and reduce its availability).
Biotinidase is an enzyme that frees biotin bound to food proteins and cycles/recycles it throughout the body.
Full or partial biotinidase deficiency occurs in approx. 1 in 60,000 newborns.
Interestingly enough, pregnancy may also affect biotin status.
Marginal biotin deficiency may be more common in pregnant women than was previously believed, and some researchers have speculated that this could result in teratogenic effects. Nonetheless, evidence that birth defects are caused by biotin deficiency is based solely on experimental animal models.
At this point in time, supplemental biotin is not being recommended for pregnant women, although increased consumption of biotin-rich foods during pregnancy would be a wise precaution.
The adequate intake (AI) level of biotin for adults is 30 micrograms (for both men and women.) Biotin supplementation is often recommended for improving brittle nails and hair, but there is little evidence to suggest that supplemental biotin has any beneficial health effects beyond treating frank deficiencies.
The exception to this might be people with diabetes, since preliminary evidence suggests that very large doses (7,000 to 15,000 micrograms) of biotin may be helpful in regulating blood sugar. However, more work needs to be done before biotin can be recommended for this purpose.
Biotin is usually included in B-complex vitamin supplements. It is generally a good idea to take multivitamin supplements that contain all of the B-vitamins rather than single supplements because the B vitamins work in concert with each other.
Biotin is not known to be toxic, and the US Institute of Medicine has not set a tolerable upper level of intake (UL). Nonetheless, there are no well-established benefits associated with biotin supplementation beyond the established adequate intake level, in the absence of clinical supervision and advice.