Study ties red and processed meats to worse colon cancer survival
The findings, published online July 1 in the Journal of Clinical Oncology, do not prove that steaks and hot dogs themselves affect a person's chances of surviving colon cancer. But experts said the study supports what's already recommended for colon cancer patients, and everyone else: Eating a healthy diet rich in fruits and vegetables, and low in red and processed meats.
"I think this underscores the importance of a lifelong healthy diet," said lead researcher Marjorie McCullough, of the American Cancer Society.
McCullough's team found that among more than 2,300 colon cancer patients, those with a high intake of red and processed meats both before and after their diagnosis were at greater risk of dying from the disease.
Specifically, patients who ate at least four to five servings per week before and after their diagnosis were 79 percent more likely to die from colon cancer than patients who consistently ate less.
In addition, patients who'd had the biggest appetite for red and processed meats before their diagnosis faced a heightened risk of dying from any cause, including heart disease or stroke.
None of that, however, proves that the high meat intake itself is to blame, said Dr. Jeffrey Meyerhardt, of the Dana-Farber Cancer Center in Boston.
"This doesn't give us enough to make definitive dietary recommendations," said Meyerhardt, who wrote an editorial published with the study. "It's suggestive of some role for red and processed meats in the overall health of colon cancer survivors."
Still, Meyerhardt agreed that the results support having a healthful diet after a colon cancer diagnosis—and ideally, your whole life.
The findings are based on more than 2,300 U.S. adults diagnosed with colon cancer that had not yet spread to distant sites in the body. Over the next seven and a half years, nearly 1,000 patients died—more than 400 from colon cancer itself.
The patients were all part of a larger study on nutrition and cancer, and had been regularly completing diet questionnaires before their colon cancer diagnosis. So McCullough's team was able to look at people's diet habits over time, and how they correlated with survival.
When the researchers looked only at pre-diagnosis eating habits, colon cancer patients who had downed the most red and processed meats—eight or more servings per week for men, and six or more for women—were 29 percent more likely to die during the study period.
But that seemed to be explained mainly by deaths from heart disease or stroke. When it came to the risk of dying from colon cancer, only people who ate a lot of red and processed meats both before and after diagnosis faced worse odds.
McCullough said there are many studies showing "convincing evidence" that red-meat-lovers are, on average, at increased risk of developing colon cancer in the first place.
The reasons are not completely clear. But, Meyerhardt said, both red and processed meats can generate certain cancer-promoting chemicals—including heterocyclic amines and N-nitroso compounds—that could damage cells in the colon lining.
That, in theory, is how the meats might raise the odds of developing colon cancer. It's not clear how they would affect colon cancer survival, Meyerhardt said.
But, he said, based on the current findings, it is "reasonable" for colon cancer patients who had been eating a lot of red and processed meats to cut down.
"This is a question patients ask all the time: 'What should I eat? Should I cut down on red meat?'" Meyerhardt said.
For now, it seems that cutting down is wise—although the question of how much red meat is OK cannot be answered, Meyerhardt said. But both he and McCullough said trimming back on steaks and lunch meat alone is not enough.
"A healthy diet includes eating a lot plant foods," McCullough said. She advised getting plenty of fruits and vegetables, whole grains—rather than the refined grains in white bread and many processed foods—and healthy fats, like those in vegetable oils.