E ven those among us who'd like to slim down a little might be understandably upset at the thought of losing weight in our brains, but it seems our brains do shrink as we age. Decreases in brain volume are associated with cognitive impairments such as memory loss, dementia and Alzheimer's disease. The good news is that British researchers recently found that some brain shrinkage may be associated with low levels of B-12 -- which suggest that perhaps supplementing might be a preventive strategy.

ABOUT THE RESEARCH

Several studies have linked B-12 deficits with cognitive decline and dementia. A. David Smith, DPhil, FMedSci, and his colleagues at the University of Oxford, set out to learn more about the association by measuring the amount of bioavailable B-12 in older people. In a five-year longitudinal study, they followed 107 individuals of both genders (mean age 73) with no mental impairments at the start of the study. Participants were given yearly exams that included cognitive tests, MRI scans and blood tests to track the amount of bioavailable B-12.

The researchers found two things. First, those whose B-12 levels were lowest at the start of the study had the most -- and fastest -- brain shrinkage over the five-year period. In addition, brain shrinkage occurred even in those whose plasma B-12 levels were still considered to be within a normal range.

TO SUPPLEMENT OR NOT TO SUPPLEMENT?

The RDA for B-12 is 2.4 micrograms, which can generally be obtained from the effective digestion and uptake of foods like meat, milk, eggs, fish and vitamin-fortified cereals.  However, poor diet and, unfortunately, the effects of aging itself lead to depleted B-12 levels.

Now, Dr. Smith and his colleagues are turning their attention to the obvious next question of whether B-12 supplements can reverse or halt the loss of brain volume once it has begun, with a study of elderly people they hope to conclude later this year. Though there is little consensus among the medical community about when B-12 supplements should be prescribed, Dr. Smith believes people over age 50 should have B-12 levels checked every five years or so, and take supplements if the levels are in the low-normal range. Have your B-12 levels checked right away if you notice symptoms of deficiency, which can include tingling and numbness in the extremities in addition to poor memory. Vegetarians and pregnant women and nursing mothers are also at higher risk for low B-12 status, so they too should discuss with their doctor whether supplementation might be advisable. Other people who might have low B-12 levels are those who take proton pump inhibitors and H2 receptor antagonists for prolonged periods.