The Evidence Is Thin on Multivitamins

Now, new findings from Tufts University show that high folate worsens that anemia in seniors and impairs cognitive function in those who also have low levels of vitamin B12.

"That's new and very unexpected," says A. David Smith, professor of pharmacology at Oxford University and author of an editorial accompanying the Tufts study, which appears in this month's American Journal of Clinical Nutrition. "We don't understand the mechanisms, but it indicates an interaction between folate and B12."

Based on the Tufts report, Smith estimates that 1.8 million seniors in the United States could be affected. "I feel quite worried about it," he says.

Those at highest risk consumed high doses of fortified food and took a multivitamin with folate. That leads Irwin Rosenberg, professor of physiology at Tufts and lead author of the study, to conclude that the problem "is not so much the fortification itself, but the added effects, the multiplier effects of fortification and taking a multivitamin."

And just as with other vitamins and minerals, there are surprises: Seniors who also had high levels of vitamin B12 were protected against the cognitive impairment from high folate intake. "Simply put," Smith writes, "if your vitamin B12 status is good, folate supplementation is good for you!"

That's why, he says, "we need to think carefully about the balance of nutrients that we take."

Here's what these scientists advise:

· If you take a multivitamin, choose one that contains 100 percent or less of the daily value for each ingredient. Doing that lessens the risk of reaching toxic levels.

· Consider taking a vitamin B12 supplement if you are 50 or older. It appears to help counter the effects of folate fortification in foods. With age, the stomach produces less acid. That reduces absorption of naturally occurring vitamin B12. Crystalline B12 found in fortified food and supplements is more easily absorbed by the aging stomach. ·