For many years, the medical consensus has been that memory loss is an unavoidable age related process.  Now, we know this may not be totally correct.  New research is showing that cognitive decline may have more to do with lifestyle choices than once thought.  There have been several dietary constituents related to brain health making headlines recently.  Last month we posted an article discussing how Vitamin C may help slow cognitive decline.  Today, we discuss an article posted in the journal Neurology that studied the effect of Vitamin B12 deficiency in relation to the advancement of cognitive dysfunction.

The study, conducted over a four year period at the Rush University Medical Center in Chicago, monitored the health status of 121 people, as it related to B12 levels measured in their blood.  Since it is  known that serum B12 levels are a poor indicator of deficiency, this study instead looked at five deficiency markers, namely homocysteine and methylmalonate.  As this can be a difficult concept to grasp, a deficiency marker for B12 is simply a marker in the blood that gets higher as B12 levels get lower.  What was found was that four out of five deficiency markers were strongly associated with cognitive decline.  People with higher B12 deficiency had poorer episodic recall and perception.  More striking, a correlation between B12 deficiency and lower brain volume was observed with MRI—those with low B12 had brains that were shrunken in comparison to those who did not.

How might a deficiency in B12 cause physiologic brain problems?  The answer may lie in the biochemistry of homocysteine.  Homocysteine is not something obtained through diet—it is a toxic by-product of metabolism that requires folic acid (B9), pyridoxine (B6), and B12 for degradation.  Therefore, when B12 levels are low, homocysteine levels increase.  There is substantial evidence explaining the negative toll of homocysteine levels on the cardiovascular system, through direct damage to the blood vessels and the deposition of atherosclerotic plaques.  Since the brain is highly vascular, any damage to the blood network in the body can have a pathologic effect on the brain.  The mechanism purposed is as follows:

  • Low B12 → Increase in toxic Homocysteine (B12 deficiency marker) → Damage to the vasculature in the brain → Cognitive decline

How can you help yourself avoid a B12 deficiency and the age related cognitive problems?  Consider these solutions:

  • Eat a diet rich in healthy B12 sources: fish, poultry, dairy
  • Have your homocysteine levels measured by your doctor
  • Consider supplemental B12: injection or sublingual
  • Have your doctor ensure you do have a B12 absorption issue


Neurology September 26, 2011 vol. 77 no. 13 1276-1282