High levels of vitamin D in the bloodstream do not appear to reduce the risk of seven less common cancers: endometrial, esophageal, stomach, ovarian, pancreatic, kidney, and non-Hodgkin’s lymphoma. In fact, there was a suggestion that people with the highest vitamin D levels may have an increased risk of pancreatic cancer. These results were reported in a series of studies published in the American Journal of Epidemiology.
Vitamin D is a fat-soluble vitamin that comes from dietary supplements, foods such as fortified milk and cereal, certain kinds of fish (including salmon, mackerel, and tuna), and exposure to sunlight. Long known as an important factor in bone health, a quickly growing body of evidence now also shows that vitamin D may help lower the risk of cancer, heart disease, and even premature death. Several studies have shown a link between vitamin D and a reduced risk of colon cancer.
While some data suggests that vitamin D may reduce the risk of several other less common cancers, no single study could address the risk due to small study sizes. Instead, researchers pooled data from 10 studies in order to better assess the link between vitamin D and these cancers. The study—called the Cohort Consortium Vitamin D Pooling Project of Rarer Cancers—measured blood levels of 25-hydroxy vitamin D (the primary form of the vitamin).
After analyzing the data, researchers did not find evidence that high vitamin D levels reduced the risk of these particular cancers. In fact, people with the highest circulating vitamin D levels appeared to have an increased risk of pancreatic cancer.
Research will likely continue regarding the importance of vitamin D. Although it does not appear to reduce the risk of these less common cancers, it is still an important component of bone health. Finding middle ground is likely to be important—vitamin D levels that are too low or too high may increase health risks.