The multivitamin maze

Nutrition Action Healthletter, March, 2006 by Bonnie Liebman, David Schardt

Shopping for a multivitamin is like trying to hit a moving target.

Each supplement has at least 20--and sometimes 40 or 50--ingredients. Combine that with the evolving science ("beware of excess vitamin E," "bones need more vitamin K," "don't overdo vitamin A") and the claims on the packages ("More energy boosting ingredients!" "More cell-protecting antioxidants!" "Helps promote a healthy heart!") and you've got the makings of a migraine.

That's just the beginning. How are people supposed to know if they need lycopene, lutein, ginseng, ginkgo, or digestive enzymes? No wonder stress vitamins sell so well.

Here's our guide through the multivitamin maze.

1 Watch out for too little.

A good multi should supply roughly 100 percent (or more) of the Daily Value (DV) for most vitamins and minerals. Exceptions:

* Calcium and magnesium are bulky, so the only multis that have a day's worth require you to take two or more capsules a day. Don't bother. Look for 100 milligrams (mg) of magnesium (25 percent of the DV), which can easily fit into a single pill. Get your calcium from foods or a separate supplement.

* Chromium, selenium, and zinc should be there, but may be missing. Our Best Bites didn't have to have 100 percent of the DV for each, though, because the DVs haven't been lowered to match the latest recommendations from the Institute of Medicine (see p. 6).

Among the popular brands that fall short of the IOM's recommended levels for selenium: Geritol Complete, GNC Preventron and Solotron, One A Day (Active, Essential, and Maximum), Whole Foods Daily, and Centrum (regular, Silver, and Chewables) and its copycats.

* Vitamin K. The DV is 120 micrograms (mcg), but research suggests that people need more to reduce the risk of a hip fracture. Many multivitamins have little or no vitamin K, probably because it can interfere with blood thinners like Coumadin (warfarin). If you take a blood thinner, check with your doctor before taking a multi that contains vitamin K.

We gave Best Bites to multis with lower levels of vitamin K--at least 25 mcg for men and premenopausal women and at least 10 mcg for anyone 50 or older--only because in each case it was tough to find more. You can also get vitamin K from leafy greens like romaine lettuce and 2 spinach.

2 Watch out for too much.

In their competition for customers, some multivitamins go overboard. Our chart includes only brands that limit their beta-carotene, iron, magnesium, phosphorus, and vitamin B-6 to safe levels. Best Bites also limit vitamin A acetate or palmitate, vitamin E, and zinc. Here's why:

* Vitamin A acetate or palmitate (retinol). Too much can raise the risk of hip fractures. The Tolerable Upper Intake Level--the most you can take without worrying about any adverse effects--is 10,000 IU (International Units) a day, but if you get that much in a multi, whatever you get from foods would put you over the top. Among the multis with at least 10,000 IU: KAL (Mega Vita-Min and Multi-Four ), NOW Vit-Min 75 , Solaray (Multi-Vita Mega-Mineral, Provide, Spectro, and Three Daily Super-Energy), and TwinLab Vita Quick.

* Vitamin E. The Vitamin Shoppe Multi-Vitamins pack has 1,000 IU of vitamin E. That's too much, considering that an analysis of 19 trials found that the risk of dying rose steadily as the vitamin E dose increased from 100 IU to 2,000 IU a day.

* Iron. The highest safe level is 45 mg, from supplements and food combined. Given how much iron people get from red meat and other foods, the 25 mg in some multis could bring you close to that max. Too much iron from pills can cause constipation or (if you're genetically susceptible) iron overload. The jury is still out on whether excess iron can increase the risk of heart disease and cancer.

* Zinc. You need only 8 mg (women) or 11 mg (men) per day. Too much zinc can make it hard to absorb or retain copper. (At doses close to 300 mg a day, zinc can also impair the immune system.) The highest safe level is 40 mg, but that includes zinc from food. So it's wise to avoid the 30 to 35 mg in some formulas and the SO mg in Solgar Male Multiples and The Vitamin Shoppe Mature Male pack.

3 What do YOU need?

For some nutrients, how much you need depends on who you are:

* Iron. Many brands have 18 mg because that's the Daily Value, but only premenopausal women (who lose iron during menstrual periods) need that much. Men and postmenopausal women need 8 mg a day, but the 9 or 10 mg in many multis is close enough. Think twice before you switch to an iron-free multi, though. If you rarely eat red meat, you may run short on iron, especially if you donate blood regularly.

* Vitamin B-12. The DV is only 6 mcg, but some experts recommend 25 mcg a day if you're over SO. In theory, people who take acid blockers like Pepcid, Prilosec, Prevacid, Tagamet, or Zantac may be less able to absorb B-12, but few studies have looked. To play it safe, take 250 to 500 mcg a day of B-12 if you take acid blockers daily (you'll probably need a separate supplement). High levels of B-12 have no known side effects.