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iccky · 11-14-2006, 08:40 PM

The science suggests that taking a daily multivitamin doesn't do much good, but probably doesn't hurt either. So figure that while you should probablly take one, don't waste a lot of time or money on it.

http://www.chicagotribune.com/entert...t_shopping-hed

Quote:

Studies shed negative light on use of the multivitamin
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Harvard Health Letter

October 24, 2006

Studies have raised doubts about vitamins, but the multivitamin pill is still 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 convenience and cravings lead us astray. The multivitamin is partial protection from our lapses.

It's also an easy way to add surplus vitamins and minerals to our diets. By definition, vitamins are organic (carbon-based) compounds needed in only small amounts. Minerals serve a similar purpose but are inorganic. Historically, nutrition focused on vitamin deficiencies that cause disease. But with fortification -- the systemic addition of nutrients, chiefly vitamins, to the food supply -- and no shortage of food, the focus changed to whether vitamins and minerals in amounts larger than we need might protect us against conditions such as heart disease and cancer.

Some people scarf down megadoses, an approach with which most experts disagree. 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 has been looking like they might not, as high-profile studies have come to negative conclusions.

It's well established that a dose of B vitamins -- B-6, B-12, and folate -- lowers homocysteine, an amino acid that is a risk factor for heart attack, stroke and dementia. The logical supposition: Having an ample supply of those B's coursing through your veins (and arteries) could improve your chances of avoiding cardiovascular disease and cognitive decline.

But results from a large randomized controlled trial published in the New England Journal of Medicine in April 2006 showed that while the B vitamins lowered homocysteine levels, that didn't result in fewer heart attacks or other major cardiovascular events. A second disappointing study was published in the journal in June 2006. Despite their homocysteine-lowering prowess, B vitamins were no better than a placebo at protecting people from cognitive decline.

Vitamin E hasn't been faring too well, either. Johns Hopkins researchers dubbed 2005 the annus horribilis for the vitamin because of all the disappointing studies, chief among them their meta-analysis that found that large daily doses (400 IU and up) increased mortality risk.

The National Institutes of Health convened a meeting on multivitamin and mineral supplements last May. The NIH holds these "consensus conferences" several times a year on a variety of subjects. Experts listen to presentations by other experts for a couple of days, then issue a "state of the science" statement.

In this case, the statement was extremely cautious. Present evidence is "insufficient to recommend either for or against the use of multivitamin/multimineral supplements by the American public to prevent chronic disease," was the inconclusive conclusion. The experts 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 and already have healthy diets.

Dr. Walter Willett, chairman 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 spate of negative study results.

Those results have come from randomized controlled trials, which usually are regarded as the gold standard. But there are problems with clinical trials too. They often are fairly short, so a nutrient's long-term consequences may be missed. For example, Willett said that beta carotene didn't look like it was having any effect on cognition at the 12-year mark in Harvard's Physicians' Health Study, but at 18 years, benefits were detected.

There also often are questions about how applicable the results of clinical trials are. Some of the negative findings have come from studies that enrolled people who had vascular disease or diabetes. High-risk individuals tend to have more "events," so there is more data for analysis, and the results are more reliable statistically. But how relevant are the findings to healthier people? With the B vitamin research, it's the reverse: The patients in those studies had homocysteine levels that were normal or just slightly elevated, so the results may not apply to people with higher levels.

Multivitamins already are part of some official recommendations. The federal government's 2005 Dietary Guidelines suggest that people older than 50 take them as a way to ensure adequate vitamin B-12 intake. And the U.S. Centers for Disease Control and Prevention advises all women of child-bearing age to take folic acid -- and a multivitamin is also a good way to do that -- because doing so lowers the risk of birth defects. That leaves men age 50 and under as the only adult group not covered.

I was always kind of skeptical. I mean, your body is designed to take in these compounds a little bit at a time over the course of the day, in the context of normal food. We expect it to absorb and make as efficient use of these vitamins and minerals when they're dropped into our system is a single pill early in the morning? I doubt it.