Q: Can you overdose on supplements of vitamin C, vitamin E, and vitamin A?
– Monika in Pittsburgh

A: Yes, you can overdose on almost any nutrient. For example, even moderate daily doses of 10,000IU of vitamin A are suspected to increase risk for birth defects in pregnant women, which is why this vitamin is limited to 5,000IU in prenatal supplements. Since one out of two pregnancies are unplanned, all women during the childbearing years should limit intake of vitamin A to this amount. Vitamins C and E are relatively non-toxic, but can have side effects if dosages are high enough. While 250mg to 1,000mg of vitamin typically is safe for adults, these amounts could be toxic for small children and larger doses of several grams can cause stomach upsets in adults. Vitamin E is safe in doses up to 400IU or more, although people taking anticoagulant medications should consult with their physicians before taking more than this, since this vitamin is a blood-thinner. -Elizabeth Somer

Q: How much over the RDA would be wise and safe in taking vitamin E for arthritis and premenstrual syndrome?
– Sue in Berkeley, CA

A: Vitamin E is a relatively safe vitamin and can be taken in doses as high as 800IU or more with little or no adverse side effects. The only concern is if you also take blood-thinning medications, since vitamin E also is a blood thinner and could cause excessive bleeding if taken with these medications. Typical recommendations for vitamin E are 100IU to 400IU a day. Whether vitamin E is effective in the treatment of either arthritis or Premenstrual syndrome has not been proven, so taking doses any greater than 400IU for these conditions is not recommended without physician approval. – Elizabeth Somer

Q: Should I take vitamin E supplements and if so, how much and which ones?
– George from New Orleans

A: Vitamin E forced everyone to accept that a good diet still needs supplements by showing unequivocally that intakes of vitamin E – in amounts far greater than realistically possible from diet alone – lower heart-disease risk, protect the eyes from age-related vision loss, boost the immune system, and possibly help slow the progression of Alzheimer’s disease. How much do you need? A landmark study from Harvard showed that 100IU of vitamin E taken daily for years lowered heart-disease risk by up to 40% in men and women. If you go the diet route, you must eat 3,350 slices of whole wheat bread, more than 6 cups of cashews, 1 cup of almond oil, or 4 cups of wheat germ to meet this minimum amount! Other studies show that 200IU to 400IU lowers heart-disease risk. There doesn’t seem to be much benefit in taking doses any greater than this if you’re healthy and hope only to lower disease risk in the future. What type of vitamin E should you take? Natural vitamin E supplements are best. Natural vitamin E supplements are two times better than synthetic at making it into the tissues and raising blood levels. Look for supplements that contain only d-alpha tocopherol or the new term RRR-alpha, rather than the synthetic dl-alpha tocopherol or all-rac-alpha. If you can’t afford the natural, take a little more of the synthetic to make up for its poorer retention. -Elizabeth Somer