Description:  A vitamin B-complex is a mixture of the eight essential B vitamins, such as thiamin (B1), riboflavin (B2), niacin (B3), pyridoxine (B6), pantothenic acid (B5), folic acid (B8), cyanocobalamin (B12), and biotin. Most of the B vitamins play a critical role as cofactors in cellular energy metabolism. B vitamins are important for hundreds of biochemical reactions in the body. B vitamin deficiency can lead to fatigue and lethargy, which is why B-complex supplements are excellent energy boosters and anti-stress formulas. Vitamin B12 is not synthesized from plants or animals, and process of absorbing B12 is very complex. Because of this complexity, B12 absorption may be compromised, potentially leading to B12 deficiency. Thus, absorbability is a key factor in choosing B12 supplementation.