The association between red and processed meat consumption and risk of developing colorectal cancer has been widely demonstrated, but what hasn't been known was whether there was an impact on outcomes.
It is an important question to ask, but it hasn't been answered yet.
An American Cancer Society study investigating diet and survival in 2,315 patients who developed colorectal cancer while participating in the ACS's Cancer Prevention Study-II Nutrition Cohort confirms an elevated risk of mortality from any cause in those who ate the most red and processed meat, but the study could not connect worse cancer-specific survival with high consumption levels of red meat and processed meat in the diet after diagnosis.
In the study, published in the August 1 issue of the Journal of Clinical Oncology (2013; 22:2773-2782), colorectal cancer patients who reported consuming the highest amount of red and processed meat before diagnosis had a 29 percent higher risk of all-cause mortality compared with those consuming the least amount. But, cardiac mortality was the major cause of death, and self-reported meat consumption after colorectal cancer diagnosis was not independently associated with mortality.
Still, the study authors say the data are relevant because cancer survivors in general are at a greater risk of chronic diseases such as heart disease.
“Our main finding was that men and women who consumed the most red and processed meat before diagnosis had a 29 percent increased risk of death from any cause, compared with men and women who consumed the least,” said first author Marjorie L. McCullough, ScD, RD, Strategic Director of the ACS's Epidemiology Research Program.
McCullough said the researchers did not have data on colorectal cancer recurrence, only data on what individuals diagnosed with colorectal cancer died from, and that included colorectal cancer-specific deaths, cardiovascular deaths, and all other causes combined.
In an accompanying editorial—“We Are What We Eat, Or Are We?” (JCO 2013; 31:2763-2764)—Jeffrey Meyerhardt, MD, MPH, Clinical Director of the Gastrointestinal Cancer Center at Dana-Farber Cancer Institute, said that although a message that diet before diagnosis influences outcomes may seem to have limited utility for someone who has already developed cancer, the information does further strengthen the recommendation to maintain a healthy diet and lifestyle throughout life to maximize health benefits.
Still, “the findings are not as clean of an answer one would have hoped or expected from looking at this question,” he said in a telephone interview. “It is important to ask the question [about diet after colorectal cancer diagnosis], but if you are a patient it is not clear you are impacting your colorectal cancer by eating red or processed meat. It may be that you are affecting survival of other diseases, so maintaining a healthy lifestyle and reducing the consumption of red and processed meat may be a reasonable option to consider.”
Meyerhardt said that patients regularly ask what they can eat and how that might affect their outcome.
“As cancer patients go through treatment and survived the immediate risk of recurrence and move on with their lives, they want to know how they can stay healthy otherwise,” he said. “And in a colorectal cancer survivor, there are exposures they may want to avoid, and perhaps red meat is one of them.
“We have had other studies that looked at other exposures such as exercise and other dietary factors such as a high glycemic load where the exposure after diagnosis does seem to impact outcome,” he said. “But this study does not provide a clear recommendation of what to tell colorectal cancer patients in terms of red and processed meat in their diet.”
The study does not speak as much to patients who already have colorectal cancer as it does to the primary care patient, emphasizing the detriment that red and processed meat can have in the development of colorectal cancer, he said.
What to Tell Patients
Robert J. Mayer, MD, a gastrointestinal cancer specialist, who is Faculty Vice President for Academic Affairs and the Stephen B. Kay Family Professor of Medicine at Harvard Medical School and Dana-Farber Cancer Institute and a member of OT's Editorial Board, agreed, saying that the study reinforces the importance of being prudent about one's health overall and after cancer has been operated on and hopefully cured.
“This [consuming less red and processed meat] is one of several things that go along with daily use of aspirin, weight control, and other factors linked to better outcome and a lowered likelihood of recurrence and death,” he said in a telephone interview.
He said he would be the first to tell patients that “up to now, we are not smart enough to explain why that happens.
“I don't think we need to wait for a mechanistic answer for why this is happening, I think the data are quite compelling that a patient fortunate enough to have been diagnosed with a colon cancer that is potentially curable should marshal all of the available personal quality-of-life lifestyle initiatives to reduce their risk for recurrence and make their likelihood for cure even greater—and one of those is to limit the amount of red meat they eat.”
But, Mayer added, “this doesn't mean everybody has to be a vegan, and that periodically having a T-bone steak is committing a cardinal sin.”