Isotonix® Advanced B-Complex provides vitamins B12, B2 (riboflavin), B6, folic acid, vitamins B3 (niacin), B5, B1 and biotin that all work in a team effort. The large amount of vitamin B-12 provided in the Isotonix formula may be capable of forcing small amounts across the membranes of the intestines and carried into the body by forming a complex with intrinsic factor, a protein produced in the stomach that promotes the absorption of vitamin B12 in the small intestine. Isotonix B-Complex has a unique delivery system that works synergistically with the body's natural design for nutrient absorption making sure you receive maximum health benefits. According to Robert M. Russell of the USRDA's Human Nutrition Center on Aging at Tufts University, vitamin B12 is probably the single most important nutrient adversely affected by aging.*