The B Complex includes several important vitamins which play critical roles in maintaining good health. Vitamin B12, also known as cobalamin, is responsible for several functions including the development of red blood cells, maintaining the nervous system, and boosting metabolism. Due to its role in red blood cell maintenance, a deficiency in Vitamin B12 can lead to some serious symptoms such as poor blood clotting and irregular heart beats. Animal products are the best sources of Vitamin B12 because this essential nutrient is not synthesized or stored in plants. Calf's liver, sardines, eggs, and dairy are some of the well known food sources of Vitamin B12.