According to the results of a study published in the Journal of the National Cancer Institute, people with higher plasma levels of vitamin D may have a reduced risk of developing colon 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, including colon cancer.
To explore the relationship between plasma levels of vitamin D and risk of colorectal cancer, researchers evaluated information from the Health Professionals Follow-up Study. This study began in 1986 and enrolled more than 51,000 male U.S. health professionals.
The current analysis focused on 179 study participants who had been diagnosed with colorectal cancer and a matched comparison group of 356 study participants who had not been diagnosed with colorectal cancer.
The plasma level of vitamin D in the men with colorectal cancer was compared to the plasma level of vitamin D in the men without colorectal cancer. An advantage of assessing plasma vitamin D (rather than dietary vitamin D) is that plasma vitamin D reflects both dietary sources of vitamin D as well as vitamin D from sun exposure.
The researchers then merged their results with the results of another large study -the Nurses’ Health Study. Merging the results of the two studies provided a larger number of subjects, and also allowed the researchers to incorporate results from women (all of the Nurses’ Health Study participants are women).
- Increasing plasma levels of vitamin D were linked with a reduced risk of colon cancer in both the Health Professionals Follow-up Study and the Nurses’ Health Study.
- The relationship between plasma vitamin D and rectal cancer remains uncertain. Results from the Health Professionals Follow-up Study suggest an increase in risk of rectal cancer with increasing plasma vitamin D, while results from the Nurses’ Health Study suggest a decrease in risk of rectal cancer with increasing plasma vitamin D.
The results of this study provide additional evidence that vitamin D may be protective against colon cancer.
Reference: Wu K, Feskanich D, Fuchs CS, Willett WC, Hollis BW, Giovannucci EL. A nested case-control study of plasma 25-hydroxyvitamin D concentrations and risk of colorectal cancer. Journal of the National Cancer Institute. 2007;99:1120-9.