Vegetarian Diet May Help Prevent Colon Cancer

Issue 25 Summer/Fall 2015

Study of Seventh-day Adventists finds even better results for ‘pesco-vegetarians’

Roasted vegetables

A new study that followed almost 78,000 Seventh-day Adventists for an average of about seven years found that those who adhered to a strictly vegetarian diet had 22 percent lower risk of colorectal cancers.

Those who were ‘pescovegetarian’ – eating only fish and plant-based foods – had an even bigger (43 percent) drop in colorectal cancer risk, according to the study published in the Journal of the American Medical Association.

“These findings show improved colorectal cancer-free survival among vegetarians across a spectrum of attained ages,” wrote a team led by Dr. Michael Orlich, assistant professor of epidemiology at the Loma Linda University School of Public Health in California.

According to Orlich’s team, there’s good reason to think that cutting out meat and focusing on plants might help shield the colon against malignancy.

In prior research, “the evidence that red meat, especially processed meat, consumption is linked to increased risk [of colon cancer] and that foods containing dietary fiber are linked to decreased risk has been judged to be convincing,” the researchers noted.

They focused on Seventh-day Adventists because vegetarian regimens have long been popular in this population. The study included 77,658 men and women recruited from churches across the United States and Canada between 2002 and 2007. All filled out standard dietary questionnaires involving over 200 food items. Rates of colon cancer were then tracked up until 2014.

Overall meat consumption was low compared to the general U.S. population, Orlich’s group note. Even so, rates of colorectal cancer for those who were either strictly vegetarian or ate a diet of fish and plant-based foods was still markedly lower than that of meat-eaters.

Why might that be so? Certainly, high dietary fiber intake and low intake of red and processed meat could be a factor, the researchers said. Obesity is also a risk factor for colon cancer, and the vegetarians in the study were less likely to be obese compared to the meat eaters, Orlich’s team noted.

But why the even larger effect for vegetarians who allowed fish into their diet? According to the Loma Linda group, that finding suggests that long-chain omega-3 fatty acids – the type found in fish – might play a role. However, they stressed that only further research can confirm that.

Speaking to CNN, nutritionist Lisa Drayer agreed that a healthy intake of omega-3s could help the colon. The pescovegetarian finding, is “consistent with previous research that has found omega-3s have anti-cancer activity and that they may be helpful in the prevention and treatment of colorectal cancer,” she said.

Orlich’s team also stressed that the level of meat eaten by the meat-eaters in the study was much lower than that found in the general U.S. population. That means that, “comparisons of the [Seventh-day Adventist] vegetarians with a more typical American high meat consumption dietary pattern might be expected to demonstrate stronger effects,” they wrote.

Drayer believes the study may point to a healthy recipe for cancer prevention.

"While the study is observational and cannot prove a cause/effect relationship, it is exciting to think that in addition to regular screenings, a diet rich in fish and fiber-rich foods may play an important role in reducing the risk of colorectal cancer,” she said.