Vitamins Not Advised for Disease Prevention

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Vitamins Not Advised for Disease Prevention

News Review From Harvard Medical School

November 12, 2013

News Review From Harvard Medical School -- Vitamins Not Advised for Disease Prevention

We still don't know whether vitamin or mineral pills can help to prevent heart disease or cancer, an expert report says. Vitamin E and beta-carotene pills definitely do not prevent these diseases. And beta-carotene can increase the risk of lung cancer in smokers and former smokers. Those are the main conclusions of the report from the U.S. Preventive Services Task Force. This is a government-appointed group of experts that advises doctors on preventive care. The panel looked at the best-quality research on vitamins, minerals and health. Some pills given in the studies contained single ingredients. Others included two, three or multiple vitamins. Taken together, the studies don't provide enough evidence that these pills can prevent either heart disease or any type of cancer, the task force said. Instead, the group recommended that people eat a balanced diet that is rich in nutrients. The report is a draft. The public can post comments on the task force website through December 9. The journal Annals of Internal Medicine published the task force evidence report. HealthDay News wrote about it November 11.


By Howard LeWine, M.D.
Harvard Medical School


What Is the Doctor's Reaction?

More than one-half of Americans take some type of vitamin or mineral supplement. We spend almost $12 billion a year on them.

Are these pills really needed? Most of these same Americans get more than enough vitamins and minerals in their diets. And the people who least need supplements are the ones most likely to take them.

The most popular are daily multivitamins. They are relatively low-cost and easy to take. But so far the medical evidence doesn't support their general use.

Once again, that's the conclusion of a new systematic review of the best studies looking at generally healthy adults. The researchers could not find evidence to support the use of vitamin and mineral supplements as a way to prevent cancer, heart disease or strokes. For vitamin E, there is clearly no health benefit.

A recent study suggested that men who take a multiple vitamin daily might have a slightly lower cancer risk. However, this study was observational. Researchers compared people who chose on their own to take vitamins or not. This type of study does not prove that any ingredient in a multiple vitamin actually prevents cancer. There could have been some other reason for the difference between groups.

In general, standard multiple vitamins with minerals and products containing reasonable doses were not found to be harmful. The exception was the use of beta-carotene supplements in smokers and former smokers. This is linked with an increased risk of developing lung cancer.


What Changes Can I Make Now?

You should not need vitamin and mineral pills if you:

  • Eat a well-balanced diet that is rich in fruits and vegetables
  • Get enough calcium in your diet
  • Eat some foods or drinks fortified with vitamin D

Still, there are reasons for some people to take vitamins.

Women should take 400 micrograms of folic acid a day during their childbearing years. This is the amount in a standard multiple vitamin. Women who take in enough folic acid are less likely to have babies born with spina bifida.

People who aren't out in the sun very often may need a vitamin D supplement. We need sunlight to change the inactive form of vitamin D in our skin to the active form. Low sun exposure may cause a lack of vitamin D in our bodies. We need enough vitamin D to maintain bone health.

Most people in the upper half of the Northern Hemisphere don't get enough sunlight during winter and most of spring and fall as well. We also have been told to avoid sunlight because it ages our skin and causes some types of skin cancers.

Each standard multivitamin has 400 International Units (IUs) of vitamin D. It's very safe to take 1,000 IUs daily.

Strict vegetarians should take vitamin B12. They may also need an iron supplement.

People at increased risk of macular degeneration might benefit from a specific vitamin and mineral combination. Check with your doctor if this is something you should consider.

If you think your diet has too little of any vitamin or mineral, multivitamins are still a very low-cost way to protect yourself against vitamin deficiencies.


What Can I Expect Looking to the Future?

I do expect that someday at least one vitamin or mineral will be found to prevent cancer and/or heart disease, even in people who eat a well-balanced diet. So far, none has passed the test.

Last updated November 12, 2013

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