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Vitamin B12 is present in foods of animal origin, including dairy products and eggs. Thus, vegetarians are more susceptible to a dietary deficiency of this important nutrient. Likewise, vitamin B12 serum concentrations are reported to be significantly lower in elderly population groups compared to younger groups. It is estimated that 10% to 30% of individuals over the age of 50 have low stomach acid secretion which results in decreased bioavailability of vitamin B12 from food.
Methylcobalamin is the form of vitamin B12 active in the central nervous system. It is essential for cell growth and replication. In some people the liver may not convert cyanocobalamin, the common supplemental form of vitamin B12, into adequate amounts of methylcobalamin needed for proper neuronal functioning. Methylcobalamin may exert its neuroprotective effects through enhanced methylation, acceleration of nerve cell growth, or its ability to maintain already healthy homocysteine levels.
Vitamin B6, or pyridoxine, is an important component of the coenzyme PLP, which metabolizes amino acids.1-4 Because of its amino acid transfer ability, the body can produce non-essential amino acids from available amino groups, as well as metabolize protein and urea. Vitamin B6 is essential because of its participation in more than 140 enzymatic reactions, including protein metabolism, conversion of tryptophan to niacin, and neurotransmitter function, among others.
Found in foods such as eggs, brewer's yeast, carrots, chicken, fish, brown rice, whole grains, and cabbage, vitamin B6 (along with B12 and folic acid) plays a beneficial role in maintaining already healthy homocysteine levels within normal range.
