B-12: Low Levels Widespread.

Low vitamin B-12 levels don't just occur in older people, say researchers at the USDA Jean Mayer Human Nutrition Research Center on Aging at Tufts University in Boston. And contrary to current wisdom, meat, poultry, and seafood may not be good sources of the vitamin.

Katherine Tucker and colleagues measured blood levels and food or supplement sources of vitamin B-12 in roughly 3,000 men and women--aged 26 to 83--whose health has been tracked since 1971 as part of the Framingham Offspring Study.

A surprising 39 percent of the participants had blood levels below 350 pg/mL, the level at which neurological signs of vitamin B-12 deficiency or high homocysteine levels sometimes occur. (Too much homocysteine may raise the risk of heart disease.) And younger people were just as likely to have low levels as older people. What's more, people who got their B-12 from supplements, fortified breakfast cereals, or dairy products were less likely to be deficient than those who got more of their B12 from meat, poultry, or fish.

"Some B-12 may be lost in cooking, or the way the B-12 is bound to the protein in meats may make it less available," says Tucker.

Why would so many younger and middle-aged people be low in B-12? "Right now it's a mystery," she adds. "Some people speculate that it's due to the increased use of antacids, but we have no evidence yet."

In the meantime, taking a multivitamin with the Daily Value of B-12 (six micrograms) should protect younger people. If you're over 50, go for a multi with 25 mcg.

Amer. J. Clin. Nutr. 71: 514, 2000.