Yet one more B vitamin (and more to come) Vitamin B7 also known as Vitamin H or Biotin is also important in metabolism and the production of fatty acids and cell growth. It assists in the transfer of carbon dioxide in the body and aids in maintaining normal blood sugar. It also assists in normal adrenal function and for maintaining a healthy nervous system and metabolism
Most of our biotin actually does not come directly from food but from the bacteria in our intestines. It is found in many foods but only in small amounts. Foods that are rich in biotin include green leafy vegetables such as swiss chard and organ meats such as liver. The recommended daily allowance is 30 mcg/day.
Low biotin levels have been found in some populations most notably alcoholics, people who have had part of their stomach removed, the elderly and those with low stomach acid. Consumption of raw egg whites can induce deficiency due to a protein in them call avidin that binds very strongly to biotin making it unavailable for absorption by the body. Cooking egg whites breaks down this protein so cooked egg whites do not deplete biotin.
Deficiency is rare and causes hair loss, eye irritation, scaly red rash around the mouth, nose and genitals and neurologic symptoms such as fatigue, depression, or hallucinations.
No animal or human studies have shown any signs of toxicity even at high doses.
Biotin, like folic acid, seems to become depleted easily during pregnancy and deficiency also increases the risk for birth defects. Therefore woman who are or plan to become pregnant are recommended to take a prenatal vitamin with biotin in addition to folic acid.
A 2006 study by Singer et al showed that chromium and biotin supplementation together significantly improved glucose levels and triglycerides in diabetics. This was confirmed in a 2008 study by Albarracin et al, and a 2013 study by Sahin et all done with rats showed the likely enzymes affected by this supplementation that explain this beneficial effect.
Veterinarians had been using biotin for defects in hooves and claws for decades so some scientists started to look into if it would work for brittle nails in humans. And indeed some small uncontrolled studies have shown that biotin is effective in treating brittle nails.
Some studies back in the 1960s showed that biotin injections given to a nursing mother could improve seborrheic dermaitis in the infant. These were small studies and were not placebo controlled. No large follow-up studies have been done. Two very small (less than 20 patients) studies were done giving biotin directly to the infants and found no effect of biotin on seborrheic dermatitis.
Overall biotin deficiency seems rare and supplementation, much like the other B vitamins, has been rarely studied and its effect on disease has hardly been explored at all. However, I feel the research concerning diabetes is compelling and this combined with the research on Vitamin B1, thiamine improving neuropathy in diabetics makes a strong case that all diabetics should be on vitamin B complex supplementation. It would be an easy study to do by randomizing diabetic patients to placebo and vitamin B complex and monitor them over a couple of years for complications from diabetes and glucose levels to see if there is any statistical difference. Overall the research into biotin is sparse and few conclusions or recommendations can be made from what we have.
Chromium and Biotin for Diabetics – 1) http://www.ncbi.nlm.nih.gov/pubmed/17109595
Biotin given to infant for seborrheic dermatitis- http://www.ncbi.nlm.nih.gov/pubmed/132601