More Evidence of the Importance of B12 in Preventing Dementia
Last month, I had a post discussing the importance of ensuring adequate levels of both folic acid and vitamin B12 to help prevent cognitive decline:
Key Nutrients in Helping to Prevent Cognitive Decline
In a new study out this month in the American Journal of Clinical Nutrition, researchers evaluated 1779 Mexican Americans between the ages of 60 and 101, and found that those individuals with high homocysteine levels and low vitamin B12 levels were at significantly greater risk of developing dementia.
Specifically, study participants with high homocysteine levels had more than double (139%) the risk of developing dementia than individuals with normal homocysteine values. And, participants whose serum vitamin B12 levels were in the lowest third of those measured had more than 60 percent greater risk of dementia.
Vitamin B12 is used in the primary pathway conversion of homocysteine back to methionine in the methylation cycle. (Betaine, or tri-methyl-glycine, is used in the secondary pathway converting homocysteine to methionine.) Methylation reactions are fundamental to many cellular processes, including expression of genes and proteins. Without adequate vitamin B12 intake, absorption, and utilization, homocysteine levels rise and the methylation cycle is impaired.
Vitamin B12 is also critically important in the methylation reactions involved in the proper formation of myelin, the “insulation” that coats nerve cells and is necessary for proper communication between them.
An interesting note about this study is that the researchers found a significant negative relationship between vitamin B12 and dementia (low vitamin B12, high dementia risk) looking only at serum vitamin B12 levels. That’s certainly one measure of potential deficiency, but a more reliable approach would be to measure methylmalonic acid (MMA), which builds up when vitamin B12 is low and is a sensitive, early deficiency marker. Your best bet for assessing vitamin B12 deficiency is to look at serum vitamin B12, MMA, and homocysteine levels in aggregate, rather than just relying on one measure.
Vitamin deficiencies (e.g., vitamin B12, folate) may be involved in dementia and cognitive decline, but they are not the only potential causes. For more on other contributing factors, see here.
