1. Most people have low levels of B12 because it is not easily absorbed by the human body
2. There are 2 very different forms of Vitamin B12 than we can take.
Cyanocobalamin is the most common form of vitamin B12 found in supplements, but you might be surprised to learn that this form of vitamin B12 does not naturally occur in plants or animals. It is chemically synthesized in a lab.
As the name implies, Cyanocobalamin actually contains a tiny amount of cyanide…it’s certainly not enough to be toxic but it does have to be removed by your body.
The other form of vitamin B12, Methylcobalamin, is better absorbed by the body and retained in higher amounts within your tissues. Methylcobalamin is the specific form of B12 needed for a healthy nervous system and is generally more efficiently used by the body. This is actually the vitamin B12 compound that doctors use to treat patients with vitamin B12 deficiencies.
The most well studied use of methylcobalamin has to do with sleep. Evidence suggests that methylcobalamin is needed for the synthesis of melatonin and can help regulate melatonin secretion, enhance light-sensitivity, and normalize your “circadian rhythm” (your 24-hour clock)
Because of this, individuals supplementing this form of B12 often have improved quality of sleep, will require less sleep, and will not report that they feel more refreshed and full of energy the following day.
Methylcobalamin also seems to result in a better 24-hour maintenance of body temperature. Typically individuals supplementing this specific form of B12 have higher temperatures in the later hours of the daytime which corresponds with improved alertness and higher metabolic rates (also why vitamin b12 shots have been shown to help with weight loss).