How to avoid common mistakes and choose the right supplement

Supplements and vitamins are great ways to make sure you're getting the nutrition a healthy body requires. Before you make a purchase, check out how to avoid some common mistakes and select the right supplement.

A rising tide of studies shows that antioxidants in pill form simply don't work — or may even be dangerous.

• And added herbs for memory or your prostate may be present in tiny, ineffective doses or create unwanted side effects and interactions with prescription drugs you may be taking.

Your body doesn't care if the vitamin C comes from rose hips or was produced in a big vat somewhere.

• And unless you've got an allergy or sensitivity to ingredients such as wheat, lactose or rice, you shouldn't pay extra for allergen-free types.

A multi that provides sufficient levels of important vitamins and minerals shouldn't cost you more than $30 a year.

• You can keep costs lower by buying on sale; just check the expiration dates to be sure you'll take them all before then.
• Multivitamins will keep for about a year in a cool, dry place.
• You don't need a fancy, expensive pill. A moderately priced name brand or store brand is usually just fine.

More than 5,000 IU per day of vitamin A from retinol may increase osteoporosis risk.

• Look for supplements containing no more than 2,500 IU of retinol-based vitamin A (it may be listed on the label or in the ingredients as vitamin A acetate or palmitate).
• Less risky: vitamin A that comes from beta-carotene, which your body converts to A as needed.
• A big caution: If you smoke, keep levels of even supplemental beta-carotene low since studies suggest high levels may raise lung cancer risk.

Increased iron is associated with a higher risk of heart disease. Once women stop menstruating, they stop losing iron, and men have been storing it all along.

• Most older people get plenty of iron from their diets and a low-dose supplement.
• Aim for eight milligrams or less. If your current multi contains more, toss it and switch.
• Getting too much can lead to gastrointestinal discomfort and, for 1 in 250 people, may trigger a potentially fatal iron-overload condition called hemochromatosis.

You just don't need more than the Daily Value for chromium, copper, iodine, manganese, molybdenum and zinc. And most of us take in sufficient quantities of chloride, magnesium, phosphorus and potassium from a healthy diet.

• Don't worry about sci-fi-sounding trace elements like boron, nickel, silicon, tin and vanadium. Experts aren't sure we need them at all.

Contact your doctor to find out which vitamins you're lacking in and keep these tips in mind to select the right supplement.