What vitamins to take and which to avoid

Americans love to take their vitamins. More than 150 million Americans take dietary supplements according to the Council for Responsible Nutrition, a supplement industry trade group. But it’s hard to know what vitamins to take – any grocery store aisle has a dizzying array. That's why this week the Empowered Patient asked two wellness experts what supplements they take every day – and what supplements they say you shouldn’t take.

Dr. Andrew Weil; Age: 66; director, Arizona Center for Integrative Medicine; drweil.com

What he takes:

1. A daily multivitamin/multimineral

2. Vitamin D. Vitamin D deficiency has been linked to breast cancer, colon cancer, prostate cancer, heart disease, and multiple sclerosis, as well as other conditions. Studies show many of us are vitamin D deficient. Weil says look on the label to make sure you're getting vitamin D3, not vitamin D2.

3. Magnesium. Lack of magnesium may lead to irritablity, muscle weakness, and irregular heartbeat.

4. Juvenon (or "Omega"), a compound believed to enhance cellular health and function. This supplement contains two nutrients, acetyl-L-carnitine and alpha lipoic acid. The company that makes Juvenon says benefits include "more energy," a "sharper mind", and "more restful sleep."

5. Co-Q-10, a supplement that boosts coenzyme Q10, which is produced by the human body and is necessary for the basic functioning of cells. Animal studies have found that coenzyme Q10 helps the immune system work better and makes the body better able to resist certain infections and types of cancer.

Weil, author of 10 books including, "Eight Weeks to Optimum Health," says it is important to take studies, like the one in JAMA, with a grain of salt. "I believe vitamins E and C are important as part of our antioxidant defenses, even if we have not yet documented specific preventive effects," says Weil.

What not to take

Weil says men shouldn't take iron unless they've been diagnosed by a physician as having iron deficiency anemia. He also advises against men taking calcium supplements; he's concerned they could increase the risk of prostate cancer.

Dr. Christiane Northrup; Age: "50 something;" author, "The Secret Pleasures of Menopause;" Drnorthrup.com

What she takes:

1. Antioxidant supplement

2. Fish oil. Some studies have found fish oil, which contains omega 3 fatty acids, can help lower triglyceride levels, lower blood pressure, and help depression, among other uses.

3. Calcium, which can help prevent osteoporosis - a problem in particular for older women

4. Magnesium

5. Coenzyme Q10

6. Vitamin D

Northrup, an authority on women's health and wellness and author of the new book "The Secret Pleasures of Menopause," says it is important to remember that vitamins are not drugs. They don't work the same way in the body.

"Vitamins are best taken in the correct proportions to each other," says Northrup. For example, she says if you are taking folic acid, which is a B vitamin, you'll do better when you also take the other Bs that make up the B complex. Says Northrup, "That's how nutrients occur naturally and how the body best utilizes them."

What not to take

Northrup says postmenopausal women almost never need iron, and taking too much might pose a risk for heart health.

For more tips on taking vitamins, check out my column at CNN.com/empoweredpatient