In fact, high vitamin D seems to be linked to an increased risk of aggressive disease - although the researchers emphasise that these findings might have occurred by chance.
Laboratory studies have indicated that high doses of vitamin D may cut the risk of the malignancy, but the results of epidemiologic studies have been inconsistent, according to the report in the Journal of the National Cancer Institute.
In the current investigation, which compared 749 men with prostate cancer to 781 matched 'controls' without cancer, increased levels of vitamin D were tied to a 96 percent increase in the likelihood of prostate cancer being aggressive or advanced.
On the other hand, the overall risk of prostate cancer was not influenced by the vitamin D level.
Results not conclusive
However, the associations were not significant from a statistical standpoint. Furthermore, the results were not linear, so that men with moderate levels of vitamin D had the highest risk of aggressive disease compared to those with lower or higher levels.
Nonetheless, Dr Jiyoung Ahn, from the National Cancer Institute in Bethesda, Maryland, and colleagues found that the associations were consistent in patient subgroups based on age, family history of prostate cancer, diabetes, body mass index, and other factors.
Writing in a related editorial, Drs Lorelei A. Mucci and Donna Spiegelman, from Brigham and Women's Hospital and Harvard Medical School in Boston say the findings require confirmation and "even if ultimately confirmed, should not be misinterpreted as evidence against other well-documented health benefits of vitamin D."
They write: "The weight of evidence does suggest that increased vitamin D levels - from diet, supplementation, or sun exposure - are likely to have a modest beneficial effect on the overall burden of chronic disease in the United States and other epidemiologically similar countries." – (Reuters Health, May 2008)
Moderate sun cuts cancer risk
Too little vit D linked to cancer