Vitamin B7 (biotin) is found in many foods, but generally in lower amounts than other water-soluble vitamins. Egg yolk, liver, and yeast are rich sources of biotin.

 

Whether biotin synthesized by bacteria normally colonizing the small and large intestine (colon) is released and absorbed by humans in meaningful amounts remains unknown. However, a specialized process for the uptake of biotin has been identified in cultured cells derived from the lining of the small bowel and colon (35).