B-Complex B-Complex is a nutritional supplement comprised of eight key B vitamins: Thiamin, Riboflavin, Niacinamide, B6, Folic Acid, B12, Biotin and Pantothenic Acid. The supplement also includes the essential support nutrients PABA (para-aminobenzoic acid), Choline and Inositol. B vitamins play a key role in all cellular function. They are also essential for supporting brain health, as well as the cardiovascular and nervous systems.