TOO MUCH OF A GOOD THING?

It used to be that we took vitamins to prevent deficiency diseases. But nowadays, scientific studies are showing how some vitamins and minerals may actually prevent diseases as big and deadly as osteoporosis, neural tube defects, heart disease and cancer. In our zeal to take advantage of those benefits, many of us take supplements in megadoses, hoping that if a little is good, more is better. But that's seldom the case. The fact is some nutrients are potentially toxic when ingested in sufficiently large amounts. In addition, high dosage vitamin and mineral supplements can interfere with the normal metabolism of other nutrients and with the therapeutic effects of certain drugs.

The following vitamins and minerals are ones that you should be particularly cautious about when taken in supplemental form. When choosing these supplements, stick to those that don't exceed 100% of the RDA.

• Vitamin A: When taken for a sustained period of time, vitamin A is toxic at doses as low as 50,000 IU (15,000ug of retinol) a day (10 times the RDA). Vitamin A is stored in fat, particularly in the liver, where it can cause jaundice and liver damage. There are many other toxic manifestations including: headache, nausea and vomiting, blurred and double vision, hair loss, bone pain and dry mucus membranes. On the other hand, carotenoids, which your body turns into vitamin A, are not known to be toxic even when ingested in large amounts for weeks to years, but they may turn your skin orange.