Too Much Vitamin D Ups Prostate Cancer Risk

NEW YORK JAN 12, 2004 (Reuters Health) - While it may not be a surprise that men who have too little  vitamin D in their bodies appear to be at higher risk of prostate cancer, it now appears that too much vitamin D can also have the same effect, new research reports.

Specifically, men who had the least amount of vitamin D circulating in their blood were 50 percent more likely to have prostate cancer than men whose blood contained an average amount of vitamin D.

Among men with the most vitamin D -- around twice the blood levels as men with an average amount -- the risk of prostate cancer increased by 70 percent.

Vitamin D is linked to a number of health benefits, so people who are deficient in the vitamin should make sure to boost their intake, the authors, led by Dr. Pentti Tuohimaa of the University of Tampere in Finland, write.

However, "our study suggests that moderately high levels of vitamin D for long periods may have adverse effects on prostate cancer risk," they note.

Consequently, for people looking to use vitamin D to help them reduce their risk of prostate cancer, "very high serum vitamin D may not be the appropriate goal," Tuohimaa and colleagues add.

This is not the first study to link prostate cancer to vitamin D. Earlier reports have found that lack of sunlight, which boosts vitamin D, is linked to prostate cancer, as is having low blood levels of the vitamin. Other studies have found that breakdown products of vitamin D can suppress the growth of prostate cancer cells in the laboratory.

During the current study, the largest to date on prostate cancer risk and vitamin D, Tuohimaa and colleagues measured the amount of vitamin D in blood samples from 622 men with prostate cancer and 1,451 men who were cancer-free. All participants were from Finland, Norway or Sweden.

In general, men who had high or low levels of vitamin D in their blood were more likely to have prostate cancer than men carrying around an average amount of vitamin D in their bodies.

There are a few possible reasons why vitamin D may influence prostate cancer risk, Tuohimaa and colleagues write.

Vitamin D itself could be affecting the growth and development of cancer, or it could exert its effects via calcium and phosphate, known risk factors for prostate cancer that interact with vitamin D, the authors note.

Additionally, some vitamin D comes from our diet, so prostate cancer risk may be influenced by whether people eat more or less of certain vitamin D-rich foods, they write.

SOURCE:

• International Journal of Cancer, January 2004.