Vitamin sales keep growing, but experts say Americans really need dose of common sense

Vitamin sales remain strong despite the economic slowdown as more people seek simple ways to prevent disease and the medical bills that come with it. About half of American adults say they take vitamins regularly. But do they help?

Here are some frequently asked questions about who should take vitamins, whether you get what you pay for, and how to know what you're getting.

Should everyone take a multivitamin every day?

It depends on whom you ask. "Most people have gaps in their diet that need to be filled, and a multivitamin serves that purpose," says Dr. Andrew Shao, senior vice president for scientific and regulatory affairs at the nonprofit Council for Responsible Nutrition.

A different view is offered by Dr. Darrin D'Agostino, chairman of internal medicine at the UNT Health Science Center in Fort Worth. "Very few people need supplements if their diet is fairly regular and fairly balanced," he says.

But if you want to be extra sure, taking a multivitamin every other day is probably enough, D'Agostino says. If you have symptoms you think a vitamin could help, talk to your doctor.

Will it hurt me to take a multivitamin every day?

No, says D'Agostino. But don't take more than the recommended dose.

OK then, what about megadoses?

All physicians recommend against that, D'Agostino says. Problems can crop up with the kidneys, liver, vision and more.

"I was working with a body builder whose skin took on a bright orange look," D'Agostino said. "She was taking too many vitamins of one sort, plus foods high in this vitamin."

Both Shao and D'Agostino emphasize that certain people with special needs should talk to their doctor about their nutritional needs, including elite athletes and people on fad diets or low-carb regimens, for example.

Will vitamins keep me well?

Don't bet on it.

"A number of products can support immune function in a very general way," says Shao. However, "there are products that claim they treat, prevent or cure a disease such as cancer, or protect against swine flu." Those are not proven and are not legal.

How can I be sure the vitamins I buy are pure and good quality?

Shao recommends these rules of thumb for all supplements:

Brand: Choose one that's been around a long time. "They have too much to risk to get it wrong. They're in business for the long term." It can have a "household name" or be a generic or store brand.

Cost: Higher price doesn't necessarily mean better quality. Club stores and drugstore chains charge less but have quality "comparable to brand names," Shao says.

D'Agostino says another way to check your vitamins' quality is to join, which tests a huge variety of products.

Any red flags?

Internet bargains -- if you don't know the brand or the company, don't take the risk, says Shao.

"FDA approved." That's bogus; the Food and Drug Administration doesn't test vitamins.

Too good to be true: Some vitamins try to be "all things to all people" or offer what amounts to a magic bullet, says Shao. "Some have 30, 40, 50 ingredients. A single tablet can only hold so much stuff; as you add more and more, you can put less and less of them in there," he says.

What about those 'quality seals' on the label?

Third-party organizations certify that the vitamins meet certain high standards, Shao and D'Agostino agree. USP and NSF are leading ones. However, don't be fooled by a "generic" seal that says something like "laboratory tested--quality assured," but doesn't say by whom. And don't worry if there's not a seal -- some mainstream brands don't put a seal on their label.

Are prescription vitamins better?

There's no evidence of any difference in quality when compared to over-the-counter, Shao says.

What should I know about vitamin D?

D'Agostino and Shao agree vitamin manufacturers are starting to include higher amounts of vitamin D as research underlines D's importance.

Until recently, vitamin D levels were calibrated to standards set some 70 years ago in meeting the needs of 18- to 22-year-old World War II recruits, says D'Agostino.

"Most adult vitamins have 400 iu [international units], but we need north of 1,000," says Shao.