Health Watch -- Vitamin Advice (Part 3)

Health Watch is a Public Service of the Office of News and Publications and is intended to provide general information only and should not replace the advice of a medical professional. You should contact your physician if you have questions about any of these topics.

Too much of a good thing isn't always good.

While we think of vitamins as being beneficial, some vitamins can be harmful in high doses. Dr. Jo Ann Carson, a dietitian who teaches clinical nutrition at UT Southwestern, says it's helpful to look at the Dietary Reference Intake numbers related to supplements. These numbers include the Recommended Daily Allowances, or RDA, and the Tolerable Upper Intake Levels, or UL. The UL is the upper limit on safe dosage for a nutrient.

For some vitamins, going above the RDA doesn't cause harm. While the RDA for vitamin E is 15 milligrams, studies have shown that it's safe to take up to 1,000 milligrams a day.

On the other hand, going above the recommended dosage of vitamin A can cause liver damage and may reduce bone mineral density. Excess vitamin A consumption in pregnant women can cause birth defects. Too much vitamin D can cause nausea, headache, excessive urination, high blood pressure and kidney damage. Some minerals can also be dangerous in high doses.

It's important to talk to your doctor about your supplement needs, as well as about any possible interaction between the supplements you're taking and any medications you might be prescribed.


April 2004