Should I take a multivitamin?
By the faculty of Harvard Medical School for The Harvard Medical School Adviser

Q: I've been taking a daily multivitamin for years. But as I've gotten older, I've improved my diet. Should still take my multivitamin?

A: It's true that many studies have raised doubts about vitamin supplements. But many nutrition experts still believe that taking a daily multivitamin pill is a good idea.

The daily multivitamin pill is no substitute for a good diet. But none of us is perfect when it comes to healthful eating. We may know all about the virtues of leafy green vegetables and whole grains. But in the real world, convenience and cravings lead us astray. The multivitamin offers some protection from our lapses, at least when it comes to omissions.

Supplements make it easy to get the vitamins we need. But in many cases, we'll actually get more than we need. The accompanying chart lists the recommended daily values for vitamins for middle-age adults. Historically, n u t r i t i o n focused on diseases caused by vitamin deficiencies, which often stemmed from food shortages. But now, many foods are fortified, meaning they contain added nutrients (mainly vitamins). And with no shortage of food, the focus has changed. Researchers have studied whether vitamins and minerals -- in amounts larger than we need -- might protect us against conditions like heart disease and cancer.

Some people scarf down mega-doses of vitamins. But most experts disagree with that practice. The daily multivitamin is the cautious wager that some extra vitamins and minerals will pay off in better health even if deficiencies aren't a problem. Lately, though, it's been looking like they might not.

It's well established that a trio of B vitamins -- B6, B12 and folate -- lowers homocysteine. High levels of homocysteine (an amino acid) have been linked to a higher likelihood of a having heart attack or stroke, or developing confused thinking or memory problems (dementia). Having an ample supply of those Bs coursing through your blood, the theory went, could improve your chances of avoiding those serious health problems.

But a major study earlier this year showed that while the B vitamins lowered homocysteine levels, that didn't result in fewer heart attacks. A second disappointing study found that B vitamins didn't help protect people from dementia, either.

Vitamin E hasn't been faring too well, either. Several studies failed to show that the vitamin helped prevent disease. And one large study even found that large daily doses (400 IU and up) might actually increase the risk of health problems.

The National Institutes of Health (NIH) held a meeting of experts on multivitamin and mineral supplements in May 2006. The consensus from the meeting was very cautious. They concluded that there's not enough evidence to recommend either for or against taking multivitamin supplement to prevent chronic diseases, such as cancer and heart disease. The experts also noted that the heaviest users of vitamin and mineral supplements are Americans who probably need them the least: people who are well educated, have higher incomes, exercise regularly and have healthy diets.

Dr. Walter Willett, chair of the Harvard School of Public Health's nutrition department, has suggested that taking a multivitamin daily is a form of nutritional insurance. He still says it's a good policy, despite the recent negative study results. Also, the federal government's 2005 Dietary Guidelines suggest that people older than 50 take a multivitamin as a way to make sure they're getting enough vitamin B12. Many older people don't absorb the vitamin very well from natural foods that include meat and eggs, but they can absorb the B12 added to fortified grains such as cereals and from multivitamins. Low levels of B12 can lead to anemia and neurological problems.

And the Centers for Disease Control and Prevention advises all women of child-bearing age to take the B vitamin folic acid, because doing so lowers the risk of birth defects. A multivitamin is also a good way to do that.

Perhaps the best argument in favor of the beleaguered multivitamin is that it's a good way to get vitamin D. Vitamin D is important for strong bones, and new research holds out hope that it may help fight cancer. But now that many of us avoid sunlight to save our skins, many Americans are deficient in the sunshine vitamin." Since fortified milk and oily fish are the only important dietary sources of vitamin D, supplements make good sense. A multivitamin is a step in the right direction.

If you take a multivitamin, be sure to buy a major brand name or store-brand product. When Consumers Union tested cut-rate products, it found that almost half didn't contain the listed amount of at least one nutrient. And above all, don't skimp on your veggies.

Copyright 2006 the President and Fellows of Harvard College. Developed by Harvard Health Publications (www.health.harvard.edu). Distributed by UFS. Submit questions to harvard_ adviser@hms.harvard. edu.