What Supplement Makers Don't Want You to Know

More is not better when it comes to the ingredients in your vitamin supplement. When a multivitamin pill is packed with extra nutrients or herbs along with vitamins and minerals, it's not the bargain you think it is, says Dr. James Dillard, former clinical medical adviser at the Rosenthal Center for Complementary and Alternative Medicine at Columbia University.

Why? A tablet or capsule can only hold so much, and the more ingredients in a single pill, the less of each ingredient you can have; sometimes pills have so little of each nutrient, they are hardly worth taking, he says.

That can hurt if you think you're protecting yourself, especially if you're a woman who needs extra calcium, says registered dietician Samantha Heller.

"Calcium should always be taken as a separate supplement, as they simply can't fit all a woman's needs into one multivitamin pill," says Heller, a New York University Langone Medical Center nutritionist and satellite radio host.

TOO MUCH OF A GOOD THING

Vitamin supplements with nutrient levels that soar above the recommended daily amounts (RDA) can also cause problems, increasing the risk of such side effects as diarrhea and nausea, Heller says.

Too much vitamin A and D, for example, can be toxic, she notes. A vitamin supplement can even make you feel ill.

According to Dillard, nuances in the way vitamins are made, or even the source of the nutrients themselves, can affect the way you react to any specific supplement. That can result in everything from dizziness to headaches, fatigue, hives or other allergic reactions.

"If you take a vitamin supplement and don't feel well, switch brands," Dillard says.

But which brand should you take? Many experts say that the bigger, more experienced companies are more likely to give you a higher quality product. Also important is a product with no sugars, starches, binders or fillers.

THE DISSOLVE FACTOR

Another key concern is getting the nutrients into your bloodstream, a goalthat's often defeated when supplements are made with a hard-shell coating.

"If we X-ray someone's stomach, we can often see dark shadows indicating undissolved vitamin pills," Dillard says.

Look for products that carry the US Pharmacopeia seal of approval, usually noted as "USP Approved" on the label. This means the product was tested by a government agency and will dissolve in a minimum amount of time.

Here's a home test suggested by Dillard to see how well your vitamin dissolves—mix equal parts water and vinegar in a glass and drop in your vitamin pill. Within 40 minutes, it should be well on its way to being dissolved. If it's not, he says, it's probably going to pass through your body undigested.

Finally, always check the expiration date before buying a vitamin supplement. If you don't find one, don't buy the product.