Get glowing! Often called "the beauty nutrient" because of the nourishment it delivers for healthy hair and scalp, this member of the B-vitamin complex is a key cofactor of enzymes involved in fatty acid metabolism, helping to supply cells with energy. Swanson Biotin delivers 5,000 mcg (5 mg) of D-biotin, the naturally occurring, biologically active form. One reviewer states that Swanson Premium is the best biotin brand because of its small pill size compared to other brands.