Colon cancer patients who have high levels of vitamin D in their blood have a reduced risk of death compared to patients who are vitamin D deficient, a new study says.

Researchers at the Dana-Farber Cancer Institute and the Harvard School of Public Health analyzed blood samples from 304 patients, and ranked vitamin D levels by quartiles (the top 25 per cent, the next lowest 25 per cent, and so on). Patients in the bottom quartile were considered to be vitamin D deficient.

They found that patients in the highest quartile, who had the highest vitamin D levels at least two years prior to diagnosis, were 48 per cent less likely to die from any cause, including colon cancer, compared to those in the bottom quartile. The risk of dying from colon cancer was reduced by 39 per cent.

"Our data suggest that higher pre-diagnosis plasma levels of [vitamin D] after a diagnosis of colorectal cancer may significantly improve overall survival," the study's authors wrote.

"Future trials should examine the role of vitamin D supplementation in patients with colorectal cancer."

The findings, the first to analyze the relationship between vitamin D and colon cancer survival rates, are published in the June 20 issue of the Journal of Clinical Oncology.

The researchers said that further study is required before doctors start recommending vitamin D supplements as a part of colon cancer treatment.

Previous research has shown that high vitamin D levels can reduce the risk of developing colon and rectal cancer by 50 per cent.

An upcoming study will involve giving vitamin D to colon cancer patients in addition to chemotherapy following surgery, to determine if the supplements offer any additional benefit.