Vitamin D May Be Cancer Fighter, UCSD Study Says

Maintaining high blood levels of a certain Vitamin D compound might reduce the risk of developing colorectal cancer by as much as 80%, according to results of a joint study conducted by UC San Diego’s School of Medicine and Johns Hopkins School of Hygiene and Public Health.

Colorectal, or colon, cancer is the second leading cause of cancer death in the United States, with more than 150,000 new cases and 61,000 deaths reported each year.

The risk of developing colon cancer seems to be “strongly related to sunlight exposure and dietary sources of vitamin D,” according to UCSD Professor Cedric Garland, principal author of the study described in the Nov. 18 issue of The Lancet, a British medical journal.

Garland on Tuesday cautioned against consuming large amounts of vitamin D in pill form because the vitamin is toxic in high doses. The specific vitamin D compound described in the study could best be increased by drinking fortified milk and eating fish such as tuna and salmon, Garland said.

The research described in The Lancet article drew cautious optimism Tuesday from the medical community.

The findings are “not yet supported by any other groups at this time,” according to Dr. Paul Goldfarb, a past president of the San Diego unit of the American Cancer Society.

“It’s nice to think that eating (healthy foods) and leading a moderate life could reduce the risk of colon cancer,” Goldfarb said Tuesday. “But what people need to understand is that, in the here and now, the way we find colon cancer is . . . (through) physical examinations. The ACS recommends that Americans begin having colon examinations at age 50.”

Cancer Society guidelines suggest that Americans can best avoid colon cancer by maintaining appropriate body weight, exercising regularly, drinking alcohol in moderation, and increasing the consumption of fruit, vegetables and whole grains.

“A paper like this does draw attention to the possible role of vitamin D in colon cancers,” said Diane Birt, a nutritional biochemist at the University of Nebraska Medical School’s Eppley Institute for Research in Cancer. “But it’s only preliminary evidence, and it’s important to remember that vitamin D is extremely toxic, especially for youngsters and infants.

“Given (the ACS guidelines), what Garland is suggesting falls within a normal, healthy diet,” Birt said.

Garland said the research was based on blood samples drawn from 25,620 healthy men and women in 1974. The blood was frozen until this year, when researchers thawed samples from 34 patients who developed colorectal cancer and 67 “control” volunteers who had not developed cancer.

“Those who developed colon cancer were deficient in vitamin D,” Garland said. “The laboratory data provide the most direct, conclusive evidence to date, and make an exceptionally strong case for the protective effects of vitamin D.”

“The next step would be clinical trials” to document the vitamin D compound’s role in reducing the risk of colon cancer, Garland said.

“We’d put people who have had colon cancer on vitamin D and see, if over the next few years . . . they have a lower incidence of recurrences, complications and deaths,” Garland said.