Vitamin B12 and your Brain

November is Alzheimer's Disease Awareness Month--but there's not a whole lot of good news to report.  Despite lots of research, we don't seem to be making much progress towards more effective treatments or cure.  And the clock is ticking. With the number of American seniors projected to double in the next twenty years, the number of people with AD will skyrocket as well.

According to the Alzheimer's Association, the only official risk factors for AD are your age, family history, and possession of the APEO-e4 gene, or "Alzheimer's gene."  But there appears to be a fairly solid link between your B12 intake (and/or your B12 blood levels) and your risk of dementia and Alzheimer's disease. 

That doesn't mean that B12 deficiency causes AD.  And it doesn't mean that increasing your intake of B12 will necessarily prevent AD. But still, these findings are worth paying attention to. 

B12 and Your Brain

The leading theory is that B12 helps to prevent a build-up of homocysteine in the blood.  Homocysteine is a harmful by-product of protein metabolism. Normally, it is recycled into harmless compounds but deficiency of B vitamins (in particular, B6, B12, and folic acid) can slow down the recycling process and allow it to build up in the bloodstream.

Higher levels of homocysteine have been linked to a higher risk of coronary heart disease and stroke, as well as an increased incidence of Alzheimer's.

Older people, vegans, and those taking acid-blockers are at higher risk of B12 deficiency

And a recent story in the New York Times makes the argument that many of us, particularly those over 50, are at high risk of  B12 deficiency.   As we age, our ability to absorb vitamin B12 decreases significantly.  In addition, routine use of antacids or increasingly common gastric bypass surgery further impair the body's ability to absorb enough B12.  Strict vegans of any age are also susceptible to low levels of B12, which is mostly found in meat, fish, and dairy products.

Many experts are now calling for the FDA to increase the recommended daily amount of B12, especially for older people, in the hopes that this might help protect aging brains (and hearts) from disease.

What should you do?

There is not yet enough evidence to suggest a direct cause and effect between B12 intake and Alzheimer's disease. On the other hand, taking more B12 is unlikely to cause any problems.  If you'd like to buy a little extra insurance against these diseases of aging, I don't see any harm in setting your personal B12 allowance higher than the current recommendations. (You can set your own "individualized daily values" for B12 and any other nutrient on the My Preferences page.)

The current RDA is just 2.4 mcg for adults.  Three ounces of steamed clams (particularly rich in B12) provide 84 mcg.  The FDA has no recommended upper limit for this nutrient. Oral doses of up to 1,000mcg per day are often used to correct deficiency with no adverse effect. Because those with deficiency usually have problems with poor absorption, only a fraction of this dose probably is likely to make it into the bloodstream. 

In some cases, injections are required to bring B12 levels up to snuff. Your physician can test you for B12 deficiency and work with you to correct it.

Use the Nutrient Search Tool to find foods high in B12 and use My Tracking to keep track of your daily intake.  If you're over 50 or take acid-blocking medications, the synthetic B12 in a multi-vitamin or fortified breakfast cereal will probably be better absorbed than the B12 naturally found in foods.

Thanks to Colby Golder for her contributions to this piece. Colby is an Editorial Assistant at Nutritiondata.com and will soon complete a graduate degree in nutrition from Columbia University.