The benefits and risks of multi-vitamins in your diet

Multivitamins are widely viewed as your diet's backup plan:  a defense against those days when you really meant to have a salad at lunch, but the pastrami sandwich won out. Should you take them?

Maybe. Multivitamins are hugely popular, but if you eat a varied, nutrient-rich diet, you probably don't need them.

• Multivitamins have long been promoted as a modest investment with a big payoff — a daily guarantee that you'll get all the nutrients your body needs to keep running and ward off disease.
• Choosing a multivitamin can be hard enough, given the variety of products — but some experts have questioned whether you should use one at all.
• If you are healthy and eat plenty of fruit, vegetables and whole grains, then "you are probably not going to benefit from a multivitamin," says nutritionist Diane F. Birt, PhD.
• Granted, most people's diets aren't ideal. A recent survey of the American diet, for instance, found that most adults and children don't get enough vitamin E, calcium, magnesium or potassium. The typical adult was low on vitamins A and C, too.
• Even if you don't eat a well-balanced diet, though, there is surprisingly little evidence that taking a multi will do you much good.
• Dr. Birt was on a panel appointed by the US National Institutes of Health to study the scientific literature on the health benefits of multivitamins. The panel determined that there is currently no reason to either recommend or discourage their use.
• Few studies have directly examined whether multis reduce the risk for any disease.
• Most vitamin studies have examined specific combinations of vitamins and minerals, and these offer some evidence that multivitamins may help certain people, though they are burdened by caveats.
• For example, a study involving nearly 30,000 people from small villages in China determined that supplements containing beta-carotene, vitamin E and selenium reduced the risk of stomach cancer and the overall risk of dying from any cancer.
• However, many of the people were malnourished, so the study's findings don't apply to everyone, especially people in first-world countries.

If you decide to take a multivitamin, keep three rules in mind.

1. Don't take "high-potency" supplements. They probably won't make you any healthier, but they may expose you to dangerously high levels of some nutrients, especially if you eat a well-balanced diet. As a general rule, don't take multivitamin and mineral supplements that provide more than 100 percent of the Daily Value, or DV (which is often the same as the Recommended Daily Allowance, or RDA) for any nutrient unless instructed to do so by a physician. A recent study found that 10 to 15 percent of multivitamin users consume too much vitamin A, iron and zinc.
2. Don't take multivitamins containing herbs. There is too little evidence that any offer health benefits, nor is there adequate information about the proper dosage.
3. Don't worry about form. Multivitamins are available as traditional tablets as well as chewable tablets and liquids. All work just fine, so pick the form that makes you most comfortable.

Like any dietary supplement, multi-vitamins have their place, but they may not be for everyone. Consult a doctor or dietician to see if there are any crucial vitamins you are not getting enough of in your diet, and plan a multi-vitamin regiment accordingly.