Vitamin B12 is a nutrient that helps keep the body's nerve and blood cells healthy and helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia called megaloblastic anemia that makes people tired and weak.
Methylcobalamin the most bio-available form of Vitamin B12, i.e. it is the most readily absorbed. Further to this research has shown that it remains in the body for a longer period of time and at higher levels than cyanocobalamin, which means that your body is supplied with vitamin B12 for longer if you use methylcobalamin than if you use cyanocobalamin. Methylcobalamin is used primarily in your liver, brain and nervous system, in fact methylcobalamin is the specific form of B12 needed for nervous system health. Because of methylcobalamin's importance in nervous system health, it is also an important nutrient for vision. Research has shown that methylcobalamin significantly improves visual accommodation, while cyanocobalamin appears to be ineffective. Visual accommodation is the ability to quickly shift your focus from something nearby to something further away - this is often impaired by activities such as staring at a computer screen for long periods of time. The most well studied use of methylcobalamin has to do with sleep - although the exact mechanism of action is not yet clear, it is possible that methylcobalamin is needed for the synthesis of melatonin. Research indicates that methylcobalamin can modulate melatonin secretion, enhance light-sensitivity, and normalise circadian rhythm (your body's 24-hour clock). Because of this, individuals supplementing this form of B12 often report improved quality of sleep, often will require slightly less sleep, and will not uncommonly report that they feel a bit more refreshed when waking in the morning
Vegetarians and vegans are especially prone to Vitamin B12 deficiency but it they are not alone. It is also very common among meat eaters mainly because the vitamin is so poorly absorbed in the gut particularly when people are suffering from some sort of intestinal condition. Vitamin B12 deficiency is far more widespread than you might imagine. Studies estimate that around 40% of the population are deficient and the vast majority of those would not even know about it.