According to the results of a study published in the Journal of the National Cancer Institute, higher circulating vitamin D levels may reduce the risk of death from colorectal cancer.
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. Vitamin D is hypothesized to play a role in the prevention of some types of cancer.
To explore the relationship between levels of vitamin D in the blood and cancer mortality, researchers evaluated information from the Third National Health and Nutrition Examination Survey. The study collected information from more than 16,000 individuals.
Vitamin D levels were measured in blood samples collected at the start of the study. Men, Whites, and more highly educated people tended to have higher vitamin D levels. Individuals with a higher body mass index (BMI) tended to have lower vitamin D levels. The analysis accounted for these and other factors.
During follow-up 536 cancer deaths occurred among study participants. Of these deaths 153 were due to lung cancer, 66 were due to colorectal cancer, 72 were due to other digestive cancers (esophagus, stomach, liver, and pancreatic), 28 were due to breast cancer, 47 were due to prostate cancer, 40 were due to lymphoma or leukemia, and 130 were due to other types of cancer.
- Total cancer mortality did not vary by level of vitamin D.
- Colorectal cancer mortality was lower among individuals with higher vitamin D levels. Compared with individuals with serum vitamin D levels below 50 nmol/L, individuals with levels of 80 nmol/L or higher were 72% less likely to die of colorectal cancer.
These results suggest that vitamin D may reduce colorectal cancer mortality, but not total cancer mortality.
A potential limitation of this study is that vitamin D level was measured at only a single point in time. This single measure may not be a good indicator of vitamin D levels over time. Furthermore, the relatively small number of cancer deaths limited the ability of the researchers to evaluate individual types of cancer.
The authors of an accompanying editorial write: “The relationship between nutritional factors and colorectal as well as other cancers is complicated…Randomized clinical trials of the effects of vitamin D on the incidence of colonic polyps and invasive cancer are needed.”
 Freedman DM, Looker AC, Chang S-C, Graubard BI. Prospective study of serum vitamin D and cancer mortality in the United States. Journal of the National Cancer Institute [early online publication]. October 30, 2007.