How to get the nutrients you need: vitamin and mineral supplements help you feel your best and ward off illness. To reap their benefits, you need to take them the right way - Consumer guide: how to be an educated consumer - Cover Story

Natural Health, August, 2002 by Erin O'Donnell

Magnesium

Why You Need It: Among its many functions, the mineral magnesium maintains your bones and helps your muscles relax. Food sources of magnesium include beans and artichokes.

Which Form Is Best: Physician Elson M. Haas, M.D., usually recommends magnesium citrate, gluconate, or aspartate because they're better absorbed, but he says that magnesium oxide (a common and inexpensive form) is also absorbed decently. Haas recommends taking it before bed with your calcium supplement; these two minerals work together to help your body relax for sleep.

Effective Dosage: Our experts recommend that you take 300 to 500 mg of magnesium daily, which is more than most multivitamins contain. Magnesium supplements may trigger diarrhea. Reduce your dose if this occurs.

Potassium

Why You Need It: An electrolyte (a substance that maintains your body's fluid levels), this mineral helps regulate blood pressure and heart function. Research shows that increasing your potassium intake can lower your blood pressure.

Which Form Is Best: Get your potassium by eating lots of produce. Good sources include bananas, orange juice, dried dates, and apricots. You need about 3,500 mg daily, but over-the-counter supplements contain no more than 99 mg. The small amount in your multivitamin is fine, but many practitioners advise against taking more than 99 mg daily in supplement form because it can irritate your stomach.

Effective Dosage: Take a multivitamin and eat at least five servings of fruits and vegetables daily.

Selenium

Why You Need It: The mineral selenium could be your most potent ally against cancer. A study at the University of Arizona in Tucson in 1996 found that people who took 200 mcg of selenium a day for four and a half years reduced their risk of cancer by 32 percent and their risk of death from cancer by 50 percent. Selenium, an antioxidant, appears to regenerate vitamins E and C so that they can continue to fight free radicals. Brazil nuts are an especially good food source.

Which Form Is Best: Haas recommends that you take selenomethionine, a natural form that is less easily convened in your body to potentially toxic elemental selenium.

Effective Dosage: Take 200 mcg a day with food. Be aware that doses of more than 400 mcg daily can be toxic.

Zinc

Why You Need It: Among its many functions, the mineral zinc strengthens your immune system and supports reproduction: It helps sperm develop and is needed for ovulation and fertilization. Research also suggests that taking lozenges made of zinc gluconate can help shorten the length of a cold. Pumpkinseeds and oysters are good food sources.

Which Form Is Best: Most forms of zinc work equally well, Haas says. But if you're trying to prevent a cold, use zinc lozenges or a zinc spray made of zinc gluconate.

Effective Dosage: Take 15 mg of zinc daily (the amount in most multivitamins). Because zinc can block copper absorption, make sure that your supplement also contains 1 to 2 mg of copper. To fight colds, use a zinc nasal spray four times a day or suck on zinc lozenges that contain 15 to 25 mg of zinc gluconate every two to four hours as soon as you notice symptoms. Stop when symptoms subside. Consuming zinc on an empty stomach can cause nausea, so take zinc supplements with food.