Vitamin D Newsletter
Statement regarding recent studies showing no beneficial effect of vitamin D on cancer risk
The recent set of studies by the Cohort Consortium Vitamin D Pooling Project of Rarer Cancers published in the American Journal of Epidemiology online June 18 found virtually no effect of prediagnostic serum 25-hydroxyvitamin D [25(OH)D] levels on affecting incidence for seven types of cancer: endometrial, esophageal, gastric, kidney, ovarian, and pancreatic cancer and , non-Hodgkin's lymphoma. These results are puzzling as numerous studies report reduced risk of breast and colorectal cancer with higher serum 25(OH)D levels. Also, numerous ecological studies found lower cancer incidence and mortality rates for all of these cancers. What could explain the finding of no benefit?
One possibility is that a single serum 25(OH)D level measurement does not represent the level over the course of time when it would affect cancer incidence. Several studies find that long-term ultraviolet B (UVB) doses reduce the risk of cancer. A randomized controlled trial of vitamin D and calcium supplementation found a significant benefit of vitamin D between the ends of the first and fourth years of the study.
Another possibility is that serum 25(OH)D levels changed over the course of the studies; the median follow-up times ranged from 1.7 to 10.8 years. Serum 25(OH)D levels have fallen in Australia, the UK, and the US as the result of publicity on the risk of skin cancer and melanoma from sun exposure and the need to protect oneself from the harmful UV rays. On the other hand, vitamin D supplement use has increased greatly recently due to the widespread publicity of the benefits of vitamin D in reducing the risk of cancer and other diseases.
Thus, these studies should be taken with a grain of salt.
Page last edited: 25 January 2011