September 18, 2012 in Features, Health

Play it safe when taking supplements

Anthony L. Komaroff Universal Uclick

DEAR DOCTOR K: I take vitamin and mineral supplements. Do I need to worry about getting too much of certain nutrients?

DEAR READER: Many people take individual vitamin and mineral supplements in addition to a powerful multivitamin. But ingesting too much of certain micronutrients can be dangerous. It’s harder – but not impossible – to get dangerously high amounts of micronutrients from food alone.

To play it safe, avoid taking more than the recommended dietary allowance (RDA) of any micronutrient through supplements. (To check the RDA for any supplement, visit: list-all/.)

It is especially important to avoid taking too much of the vitamins and minerals listed below:

• VITAMIN A. Most of us get plenty of vitamin A in foods – liver, milk, eggs, carrots, spinach and many other foods. Too much vitamin A in supplements can harm bones and can lead to birth defects.

• VITAMIN E. Too much vitamin E can cause bleeding, headache, fatigue and blurred vision.

• CALCIUM (FOR MEN). Recent studies have found that excess intake of calcium appears to increase the risk of prostate cancer. While not all scientists agree, I think that most men should avoid taking calcium supplements and should not consume too many dairy products.

• IRON. Large doses of iron supplements can trigger an iron overload. Some people inherit a genetic condition that causes them to absorb more iron from the gut than most people. This can damage body tissues and can raise the risk of heart disease, liver cancer, infections and arthritis. Your body can’t easily shed excess iron. Also, taking high doses of vitamin C allows your body to absorb more iron than it normally would.

• ZINC. Getting enough but not too much zinc is a bit of a high-wire act. The RDA for zinc is 8 mg for women and 11 mg for men. Yet levels higher than 15 mg can trigger side effects, such as a depressed immune system, poor healing, hair loss and interference with taste and smell. It’s best to get zinc from food sources rather than supplements.

To send questions, go to, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.

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