Supplements May Boost Prostate Cancer Risk

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Supplements May Boost Prostate Cancer Risk

News Review From Harvard Medical School

February 25, 2014

News Review From Harvard Medical School -- Supplements May Boost Prostate Cancer Risk

Taking vitamin E or selenium pills could double some men's risk of aggressive prostate cancer, a new study finds. This study took a closer look at some data from a large study that was stopped early, in 2008. Researchers stopped that study because men taking vitamin E pills showed an increased risk of prostate cancer. Selenium pills did not appear to affect prostate cancer risk in that study. The new study focused on 1,739 men from the earlier study who were diagnosed with prostate cancer. They were compared with 3,117 men without prostate cancer. This second group was matched to the first group by age and race. Researchers looked at men's natural selenium levels, before they took any supplements. For men with high selenium levels, taking selenium pills in the study almost doubled their risk of aggressive prostate cancer. Men with low natural selenium levels had an increase in cancer risk if they took vitamin E. Their risk of prostate cancer rose by almost two-thirds. Their risk of aggressive prostate cancer more than doubled. The Journal of the National Cancer Institute published the study. HealthDay News wrote about it February 21.


By Lori Wiviott Tishler, M.D.
Harvard Medical School


What Is the Doctor's Reaction?

Prostate cancer is one of the most common cancers in America. It affects 1 man in every 7 during his lifetime. Cancer of the prostate, the gland that produces the fluid in semen, is most common among older men.

Fortunately, most men with prostate cancer do not die of the disease. More than 2.5 million men in the United States are living with prostate cancer today. 

Nonetheless, with statistics like these, it makes sense that many men -- and many researchers -- want to know how to decrease the risk of developing this common cancer. This recent study in the Journal of the National Cancer Institute explores the effects of selenium and vitamin E on prostate cancer risk. 

Selenium is a trace element that can be found in seafood, meats (organ meats in particular), some grains and dairy products. It helps to create certain proteins in the body. It helps repair cells. Most Americans get enough selenium through food.  

Vitamin E is primarily found in nuts, seeds and vegetable oils. Many Americans have diets low in vitamin E, but true vitamin E deficiency is rare. Vitamin E helps to protect cells from damage.  

Given that both these agents have roles in cell repair, it is not surprising that researchers would hope that supplements might decrease the risk of cancer. After all, cancer, at its most fundamental level, is the poor regulation and repair of our own cells.

Many studies, however, have not found a benefit from selenium or vitamin E in cancer prevention. A recent study found that taking selenium pills had no effect on prostate cancer risk. And there was a 17% increased risk from taking vitamin E.

Today's study looks at the effects of selenium and vitamin E pills on prostate cancer risk, depending on how much selenium is already in the man’s body.

Men who already had high levels of selenium in their bodies nearly doubled their risk of prostate cancer if they took selenium pills! For men with low levels, selenium pills did not help prevent prostate cancer. Vitamin E increased the risk of prostate cancer.

The bottom line? As far as prostate cancer prevention goes, vitamin E and selenium don't work. They may, in fact, increase the risk of prostate cancer.

My patients are always happy to learn when supplements are good and disappointed to learn when they are harmful. Yet this article provides important information. It's also a clear reminder that -- even with "natural" supplements -- more is not always better. In this case, it's harmful.


What Changes Can I Make Now?

No one knows exactly what causes prostate cancer. We do, however, know some of the factors that increase a man's risk. These include:

  • Older age.
  • Race -- African-American men are more likely to get prostate cancer. They are also more likely to die of it than white men.
  • Family history -- If your father or brother has prostate cancer, your risk is increased.
  • Lifestyle -- There is some evidence that eating a high-fat diet can increase the risk of prostate cancer.

Doctors disagree about whether men should be tested for prostate cancer with a test called the PSA. If you are interested in it, discuss it with your doctor. It is not a good test for everyone. Learn the pros and cons and make a good decision based on your risk, your medical history and your personal preferences.

This study suggests there is no reason to take vitamin E or selenium in levels higher than the recommended daily amount. In general, I advise patients to eat a healthy, balanced diet. I'd rather see them spend their money on good, healthy, vitamin-rich food than to spend it on vitamins in bottles. However, if you do take standard multivitamins, the amount of vitamin E and selenium in these pills should not harm your prostate.


What Can I Expect Looking to the Future?

Researchers and patients will continue to look for ways to prevent cancers. I believe that we will find many of them. But we may also continue to learn that micronutrients and vitamins are safest for humans at the low levels that our bodies have evolved to need. I won't be surprised if we find that high levels of other supplements cause more harm than good.



Last updated February 25, 2014

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