May 1, 2014
News Review From Harvard Medical School -- Study Links Low Vitamin D, Prostate Cancer
Low vitamin D levels may increase the odds of developing aggressive prostate cancer, especially for black men, a new study finds. The study included 667 men. All of them were having their first prostate biopsy after an abnormal prostate exam or prostate-specific antigen (PSA) test. Researchers tested the men's blood for vitamin D. Normal levels are 30 to 80 nanograms per milliliter (ng/ml). Most of the men, both white and black, had vitamin D deficiency. Black men with the lowest levels, less than 12 ng/ml, were 5 times as likely to have aggressive prostate cancer as those with normal levels. White men with the lowest vitamin D levels were 4 times as likely to have aggressive disease. Black men also were more than twice as likely to have any type of prostate cancer if their vitamin D levels were 20 ng/ml or lower. In white men, vitamin D levels were not linked with overall prostate cancer risk. The journal Clinical Cancer Research published the study. HealthDay News wrote about it May 1.
By Robert H. Shmerling, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
This new study links vitamin D deficiency with prostate cancer. When I read about it, my first reaction was to ask: why would the researchers suspect a link in the first place?
Actually, there were good reasons to suspect a connection between low vitamin D and prostate cancer:
- Prostate cancer rates are highest in places where people are most likely to have vitamin D deficiency.
- Prostate cancer is more common among the elderly and those of African ancestry. These groups also have the highest rates of vitamin D deficiency.
- Prostate cancer tends to be more common where sun exposure is low (including northern latitudes). The skin also makes (synthesizes) less vitamin D when it's less exposed to the sun.
These observations suggest that low vitamin D might increase a man's risk of developing prostate cancer. And that's just what this new study found.
Among 667 men having a prostate biopsy for suspected cancer:
- African-American men tended to have lower vitamin D levels. Perhaps that's because darker skin pigment reduces absorption of the sun's ultraviolet radiation. The risk of prostate cancer also was higher than that of other ethnic groups.
- The lower the level of vitamin D, the higher the risk of having an aggressive form of prostate cancer. This effect was especially dramatic for African-American men.
These findings are important. Other than skin cancer, prostate cancer is the most common type of cancer diagnosed among men in the United States. Nearly 30,000 American men die of the disease each year. This new study suggests that something as simple as taking a vitamin D supplement might prevent many of these deaths. Increased sun exposure might also be helpful, but the risk of skin cancer makes this option less appealing.
These findings could help explain why African-Americans have a 60% higher risk of prostate cancer. They are also more than twice as likely to die of the disease as men of other ethnic groups.
What Changes Can I Make Now?
Learn about the factors that increase the risk of prostate cancer. They include:
- Advanced age
- Family history
- Ethnicity (as noted above)
You can take measures that may reduce your risk of prostate cancer and its complications. Here's what you can do:
- Change your diet. A low-fat diet that's high in fruits and vegetables has been linked with a lower risk of prostate cancer. Green tea and omega-3-fatty acids (found in fatty fish such as salmon, trout and tuna) may also reduce risk.
- Maintain a healthy body weight. Obesity may increase the risk of prostate cancer. Losing excess weight and avoiding obesity may lower risk.
- Get regular exercise. Some studies suggest that physical activity may lower the risk of prostate cancer.
- See your doctor for a prostate examination. If the exam reveals enlargement or suspicious lumps, your doctor may order a biopsy. This test may diagnose cancer at an earlier, more curable stage. However, the overall value of routine prostate exams is uncertain.
- Consider having a PSA blood test. There is controversy about the usefulness of this test. Ask your doctor whether he or she routinely recommends the test and why it is (or isn't) a good idea for you.
- Consider taking finasteride (Proscar) or a related medicine. These medicines can shrink an enlarged prostate and improve urination. But they may also lower the risk of prostate cancer for those at high risk. The overall benefit of this approach is controversial, however. That's because some studies have found that taking these medicines may increase the risk that if you do develop prostate cancer it will be a more aggressive type.
Screening for vitamin D deficiency is not currently a standard part of assessing prostate cancer risk. But that could change if future studies confirm this new research. Talk to your doctor about whether you should have a blood test for vitamin D and whether you should take vitamin D pills. In my view, we should not yet rely on vitamin D pills as a way to lower prostate cancer risk.
What Can I Expect Looking to the Future?
Vitamin D has been in the new a lot in recent years. This new study only adds to the list of potential benefits of getting enough vitamin D. We know it's good for bone health. We'll need much more research to show whether it's also important for avoiding cancer, heart disease and other ills. Other important questions need to be answered:
- How does vitamin D deficiency exert an effect on the risk of prostate cancer? Does the vitamin somehow prevent cell changes that lead to cancer? Does it slow the spread of tumors?
- Can vitamin D pills reduce the risk of prostate cancer (or other cancers)?
- Should healthy people be screened for vitamin D deficiency?
Stand by for more research news that answers these questions.