A new study sponsored by the National Cancer Institute has found that patients diagnosed with colon cancer who had abundant vitamin D in their blood were less likely to die during a follow-up period than those who were deficient in the vitamin. This study was conducted by scientists at Dana-Farber Cancer Institute and the Harvard School of Public Health.
The study appears in the June 20 issue of the Journal of Clinical Oncology. In it, the authors note that previous research has shown that higher levels of vitamin D reduce the risk of developing colon and rectal cancer by about 50 percent, but the effect on their later life wasn't known. To examine this question, the investigators, led by Dr. Kimmie Ng, and Dr. Charles Fuchs, both of Dana-Farber, analyzed data from two long-running epidemiologic studies whose participants gave blood samples and whose health has been monitored for many years.
They identified 304 participants in the Nurses' Health Study and the Health Professionals Followup Study who were diagnosed with colorectal cancer between 1991 and 2002. All had had vitamin D levels measured in blood samples given at least two years prior to their diagnosis. Each patient's vitamin D measurement was ranked by "quartiles" -- the top 25 percent, the next lowest 25 percent, and so on. Those whose levels were in the lowest quartile were considered deficient in vitamin D.
The researchers followed the 304 patients until they died or until 2005, whichever occurred first. During that period, 123 patients died, with 96 of them dying from colon or rectal cancer. The researchers then looked for associations between the patients’ previously measured vitamin D blood levels and whether they had died or survived.
The results showed that individuals with the vitamin D levels in the highest quartile were 48 percent less likely to die (from any cause, including colon cancer) than those with the lowest vitamin D measurements. The odds of dying from colon cancer specifically were 39 percent lower.