Although it is rarely discussed in medical or nutritional literature, biotin is important for the function of all known living organisms.1

This water-soluble B vitamin, which is present in minute amounts in every living cell, goes by many ­different names, including but not limited to coenzyme R, D-biotin, vitamin B7, vitamin H, and W factor.2 Biotin functions as an enzyme co-factor that is essential in multiple biosynthesis pathways.3


Scientists believe that excess biotin is stored in the intra­cellular mitochondria and is used in the processing and deactivation of carbon dioxide.3 After biotin is ingested in food, it undergoes several steps of chemical activation in the gut.4 Multiple strains of common gastrointestinal bacterial flora are responsible for these transformations. 


Although true biotin deficiency is not considered common in developed countries, several situations can create marginal biotin depletion. Pregnancy, conditions that inhibit colonic conversion, certain dietary practices, chronic alcohol consumption, and use of specific medications reduce the bioavailability of dietary biotin. Researchers also believe that individuals who have diabetes suffer from impaired biotin activity.

Scientists know that up to 50% of pregnant women in the United States develop a marginal biotin deficiency, especially in the early weeks of gestation.5 When supplemented in the preconception period and early weeks of gestation, certain micronutrients, such as biotin and folic acid, reduce some teratogenic conditions, including neural tube defects.5

Biotin is under intense scrutiny for the additional role it may play in preventing birth defects. In a retrospective review of pregnancies in the United States, women who did not take prenatal vitamins were twice as likely to have infants with a major birth defect as those who took standard prenatal vitamins that contain biotin and folic acid.6

Smoking may also lead to biotin deficiency. A small study found that women who smoked were significantly more likely to be deficient in biotin due to increased breakdown and excretion rates.7 With the established relationship between smoking and birth defects, the potential interrelatedness of smoking and biotin deficiency in birth defects is being actively investigated.

In patients with diabetes, biotin may lower fasting plasma glucose levels. A study of 43 persons with type 2 diabetes who took daily biotin supplements for 1 month found that the group’s levels of fasting plasma glucose decreased by an average of 45% from levels measured before the study period.8 Subsequent trials have been less impressive, but the enzymatic function of biotin does have a physiologic impact on glucose metabolism.

Biotin may have a role in the treatment of thinning hair and brittle nails, but published trials attempting to verify this potential show conflicting results.