The study -- published in the September 23 issue of The Journal of the American Medical Association and discussed at the annual meeting of the American Dietetic Association in October -- found that people who ate a diet rich in low-fat dairy products may have fewer abnormal, pre-cancerous cell growths in the colon than people on conventional diets.
This may be encouraging news for people fighting colorectal cancer, which claims more than 56,000 American lives every year, according to the American Cancer Society. About 130,000 new cases are diagnosed every year.
The Study's Results
Peter Holt, MD, of Columbia University conducted the research at St. Luke's-Roosevelt Hospital Center in New York. He examined 70 men and women who had abnormal cells that were growing unusually quickly in their colons -- a marker for colorectal cancer risk.
While one group stayed on a conventional diet, another group consumed a diet including enough low-fat dairy foods to provide 1,500 milligrams of calcium per day. The researchers then examined the participants' colons after six months and a year. On the average, people on the high-dairy diet had fewer abnormal cells, and those cells' growth had slowed. People who remained on a conventional diet continued to experience abnormal cell growth in their colons.
This isn?t the first study to show such results, Holt says. Previous research has shown that calcium helps to reduce irritation in the colon, possibly reducing colorectal cancer risk.
Vitamin D May Help
The vitamin D found in milk may play an important role in preventing the disease, said Cedric Garland, PhD, professor of preventive medicine at the school of medicine at the University of California, San Diego. Speaking at the American Dietetic Association's annual meeting, Garland explained that vitamin D helps the body absorb calcium from dairy products.
Despite these findings, Gabriel Feldman, MD, national director of the American Cancer Society's colorectal cancer research division, remains skeptical. He says the study didn't have enough subjects and didn't last long enough to generate solid evidence. He also thinks the study should have used numbers of pre-cancerous polyps to measure the effectiveness of a high-dairy diet.
Other studies have shown evidence that a diet high in dairy products may actually increase colorectal cancer, Feldman says. "Non-dairy consuming regions of the world, like Asia and the Mediterranean, have the lowest incidence of colorectal cancer."
Both Holt and Garland respond to this criticism by pointing to a much larger and longer-running study, published in 1985 in the journal Lancet, that showed a higher calcium intake could prevent colorectal cancer.
Eat a High-Fiber Diet
Regardless of the ongoing debate, the American Cancer Society and other health officials say a diet high in fiber (whole grains, rice, breads, vegetables and fruits) and low in animal fats (especially red meats) can reduce the risk of the disease.
Feldman acknowledges that studies have shown that when calcium is taken through dietary supplements, it can reduce the risk of colorectal cancer. "Considering the benefits that I've seen, I don?t think that it would hurt to increase calcium intake through low-fat dairy," Garland says.
Diet isn't the only way to prevent the cancer, Feldman stresses. He says people should get screened every year after age 50 for colon polyps, which can be removed before they develop into full-blown cancer. People need to overcome their fear of colorectal exams because they're the only way to be "100% sure" of avoiding the potentially fatal disease, he says.
"The reality is that it's nowhere near as bad as people make it out to be," he says. "The most important thing is that [exams] can help prevent cancer and save your life."