DEAR MAYO CLINIC: Is it true that a large study found that most vitamin supplements may actually do more harm than good? What supplements should I avoid? Which are worth taking? I'm 67 and in good health.




Many people take supplements as an "insurance policy" against inadequate nutrition. However, in developed countries, deficiencies in most vitamins and minerals are uncommon, unless there is a predisposing condition. Taking supplements provides these nutrients far in excess of what's necessary for good health.

Another reason people take supplements is to help prevent serious diseases. Studies have consistently shown that diets high in antioxidant-rich fruits, vegetables and other plant foods are associated with lower rates of cancer and heart disease. However, studies looking at supplements, including antioxidants such as beta carotene and vitamins A and E, haven't shown much benefit and there is some evidence they may actually cause harm.


Potentially risky vitamin and mineral supplements include:

1. Vitamin E: A 2012 review of research published in the Cochrane Database found that taking daily vitamin E supplements may increase the risk of dying prematurely.

2. Vitamin A: The same review found large doses of vitamin A supplements were also associated with an increased risk of dying prematurely. Supplementation with beta-carotene, a compound that's converted to vitamin A by the body, was also shown to increase risk of death, especially for smokers or former smokers. Since vitamin A deficiency is rare in the U.S., it's probably not worth the potential risk to take this supplement.

3. Folic acid (vitamin B-9): Most older adults consume adequate folate. Supplementation helps prevent birth defects, but evidence of other benefits has been elusive.

4. Vitamin B-6: Large daily doses of vitamin B-6 -- more than 100 milligrams (mg) -- can over time cause nerve damage.

5. Vitamin B-3 (niacin): High doses can help lower high cholesterol levels, but this should be done only under the supervision of a doctor. Side effects, including severe liver disease, can occur.

6. Iron: In healthy men and postmenopausal women, iron deficiency is rare. If you're in one of these categories and iron deficient, further evaluation may be considered. There is some evidence that too much iron is associated with adverse effects, including possibly increased mortality.

7. Trace minerals: Copper, chromium, magnesium, selenium and zinc are among the essential trace minerals. However, there isn't any solid evidence that trace mineral supplementation has any benefit in the absence of deficiency -- which is rare.

Supplements that older adults may consider taking include:




