Does vitamin D reduce the risk of many types of cancer as many studies suggest? A new study finds that high vitamin D in blood serum only reduces the risk of colorectal cancer.
No relationship was found between vitamin D levels and the overall risk of dying from cancer, according to a study published online October 30 in the Journal of the National Cancer Institute. However, higher vitamin D levels were associated with a decreased risk of colorectal cancer death.
Several epidemiological studies have supported the hypothesis that vitamin D can reduce cancer mortality by decreasing cancer incidence or improving survival. Animal and cell studies suggest that vitamin D may reduce tumor growth and induce cancer cell death. Diet and exposure to sunlight are the major sources of vitamin D.
D. Michal Freedman, Ph.D., of the National Cancer Institute in Bethesda, Md., and colleagues analyzed data from the third national Health and Nutrition Examination Survey to examine the relationship between levels of circulating vitamin D in the blood and cancer mortality in a group of 16,818 participants aged 17 and older.
After about a decade of follow-up, 536 participants had died of cancer. Cancer mortality was not related to the level of circulating vitamin D for the overall group, nor was it related when the researchers looked at the data by sex, race, or age. But higher levels of vitamin D (80 nmol/L or more) were associated with a 72 percent reduced risk of colorectal cancer mortality, compared with lower levels (less than 50 nmol/L).
“To our knowledge, this study is the first to examine the relationship between measured serum vitamin D levels and cancer mortality for selected site and for all sites combined,” the authors write.
A single study can't decisively resolve this question. Fortunately, other studies on vitamin D and total cancer risk are underway.
"Among the questions to be addressed in future studies is the relationship between vitamin D levels and future cancer risk both for individual cancer sites and for total cancer risk." The NCI and other institutes currently have a number of these studies underway, Freedman said.
A previous study found a negative association between blood serum vitamin D and both breast and colorectal cancer.
Keep in mind that vitamin D delivers other health benefits: Vitamin D Supplements Lower Risk Of Death, Low Vitamin D Linked To More Hip Fractures In Women, Low Vitamin D Ups Chronic Back Pain?, and Low Vitamin D Speeds Muscle Decline In Old Age?
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