Vitamin B12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins. It is normally involved in the metabolism of every cell of the human body, especially affecting DNA synthesis and regulation, but also fatty acid metabolism and amino acid metabolism. Neither fungi, plants, nor animals are capable of producing vitamin B12. Only bacteria and archaea have the enzymes required for its synthesis, although many foods are a natural source of B12 because of bacterial symbiosis. The vitamin is the largest and most structurally complicated vitamin and can be produced industrially only through bacterial fermentation-synthesis.
Vitamin B12 was discovered from its relationship to disease pernicious anemia, which is an autoimmune disease in which parietal cells of the stomach responsible for secreting intrinsic factor are destroyed (these cells are also responsible for secreting acid in the stomach). Because intrinsic factor is crucial for the normal absorption of B12, its lack in pernicious anemia causes a vitamin B12 deficiency. Many other subtler kinds of vitamin B12 deficiency and their biochemical effects have since been elucidated.
Vitamin B12 deficiency can potentially cause severe and irreversible damage, especially to the brain and nervous system. At levels only slightly lower than normal, a range of symptoms such as fatigue, depression, and poor memory may be experienced.
Vitamin B12 & weight loss
Vitamin B12 does not cause weight loss. It helps contribute to weight loss though by helping metabolize protein and fat. When protein and fat are metabolized, it produces energy and having energy helps people lose weight. Due to this, many dieticians and scientists say that while Vitamin B12 doesn’t help people lose weight, one of its side effects is that it does slow down weight gain because people with sufficient levels of Vitamin B12 in their diets tend to have more energy than those with a deficiency of the vitamin.
The biggest claim made by companies promoting vitamin B12 as a weight loss supplement is that it speeds the metabolism. B12 does help metabolize fat and protein but not in large enough quantities where it actually causes weight loss. Scientists, doctors and nutritionist state that the weight loss incurred by those receiving vitamin B12 shots and supplements is due to the fact that these people are eating healthier and are more active because they are trying to lose weight and not due to their increased intake of B12.