Does vitamin D have a role to play in preventing cancer, and if it does, what is the optimal dose? At the 2009 American Society of Preventive Oncology meeting in Tampa, Fla., investigators presented data about vitamin D and cancer, with conflicting results: While some studies have indicated that vitamin D can lower risk, others have deduced that vitamin D may have no effect as a preventative or, even worse, may boost cancer risk. In the end, the experts agreed that only large, prospective, randomized trials will off er definitive answers.
Lowering risk
There is a substantial body of data to support the idea that vitamin D supplementation may prevent cancer, said Donald L. Trump, MD, professor of oncology at Roswell Park Cancer Institute in Buffalo, N.Y. Because the exact role of vitamin D in cancer and human health is unclear, and links are almost all associational, the subject needs to be scrutinized in rigorous randomized trials.
Dr. Trump has explored whether low vitamin D levels could be a risk factor for prostate cancer. He measured vitamin D levels in 100 patients with recurrent prostate cancer and in controls. However, both patients and controls had similarly low levels of vitamin D, leading him to conclude that the low vitamin D levels were a reflection of Buffalo's geography and not a characteristic unique to cancer patients.
"Still, there are lots of other cities in North America at this latitude, so if this latitude is a risk factor for cancer, there are many other cities and large-population areas that are at the same risk," he said.
