A: Vitamin E is found naturally in vegetable oils, nuts, seeds, leafy green vegetables, and wheat germ. I think it’s safe to say that you need not worry about getting too much vitamin E through your diet. But supplements could be another matter. The Recommended Dietary Allowance (RDA) for females is 8 milligrams—although taking 200-800 milligrams has been considered safe. Since the labels on most supplements bottles express the amount of vitamin E in terms of international units (IU) rather than milligrams, you’ll want to know that the equivalent in terms of your recommended daily vitamin E needs is 30 IU, and that studies of vitamin E toxicity indicate that a person would have to take up to 3,200 IU per day to see any consistent side effects. 

Vitamin E’s primary role appears to be as an antioxidant, helping to combat free radicals—unstable molecules that attack other molecules in the body. Vitamin E may also help fight heart disease by inhibiting platelet clusters, which cause clots to form, as well as blocking the formation of thrombin, a potent hormone that also plays a role in platelet clustering.

While vitamin E is a powerful protective antioxidant, you should of course be careful not to overdose on it through the use of supplements. There are a number of circumstances under which you should not use the supplements or should do so only in consultation with you doctor. The first set of concerns has to do with its anticlotting properties. If you are deficient in vitamin K, which helps the blood clot, or if you are taking any doctor-prescribed anticoagulant medicines or thinners, you should talk to your doctor for advice about taking vitamin E supplements. Because vitamin E acts as an anticoagulant, if you take it on top of one of these medications, it could increase the risk of bleeding. Similarly, for anyone who is going to have extensive dental work or contemplating surgery, it is advisable to stop taking vitamin E supplements well before you go under the knife so that you won’t bleed or bruise excessively.

You should also be careful about using vitamin E supplements if you are taking drugs such as ulcer medications, cholesterol-lowering drugs, or an anti-biotic called neomycin. Consult your physician if you are taking these or other prescription drugs.