A vegetarian diet may reduce your risk of certain kinds of cancer by 22 percent, according to a new analysis from the Adventist Health Study-2.
Researchers at Loma Linda University Health found that eating a plant-based diet offers significant protection against cancers of the colon and rectum, the second-leading cause of cancer death in the United States after lung cancer.
The findings, published online in the journal JAMA Internal Medicine this week, are the first to emerge from the university’s multimillion-dollar Adventist Health Study-2 investigation that links diet to specific forms of cancer.
“The balance of scientific evidence seems to implicate red meat and processed meat as being linked to a higher risk of colorectal cancer, whereas a diet rich in fiber — not fiber supplements — is linked with lower risk,” the study's lead researcher, Dr. Michael Orlich, said Tuesday. “The vegans, lacto-ovo vegetarians, and pescovegetarians in our study all avoid red and processed meat and eat an increased amount of a variety of whole plant foods.”
The study, which tracked the food questionnaires and medical records of 77,659 Seventh-day Adventists over seven years, determined that vegetarians are 22 percent less likely to develop colorectal cancers than non-vegetarians.
Of those vegetarians, vegans were 16 percent less at risk of cancer, and lacto-ovo vegetarians, who eat milk and eggs, were 18 percent less at risk, although results for these groups did not achieve statistical significance.
The least at risk of the vegetarian groups were the pescovegetarians, or vegetarians who eat fish. They were 43 percent less likely to develop cancer.
Dr. Gary Fraser, principal investigator for Adventist Health Studies-2 and a co-author of this week’s report, cautioned against interpreting the results as a message to eat more fish.
“The main message is to avoid all meats, as the main result was that all vegetarians as a group did better than the non-vegetarians,” Fraser said in an e-mail interview. “Thus from this paper alone what one can really say is that replacing meats with vegetables, nuts, legumes, and fruits will most likely decrease risk of colorectal cancer.”
Orlich, an assistant professor of preventive medicine at Loma Linda University, said it was premature to conclude that the pescovegetarians’ impressive results were due to fish consumption.
“The differences between the pescovegetarians and other vegetarian groups may be due partly — or possibly entirely — to chance variation,” he told the Adventist Review. “Their diets also differ in other ways beside fish consumption. We will do follow-up analyses examining the specific associations of meat and fish with colorectal cancer, adjusting for the consumption of other foods.”
Non-vegetarians comprised half the participants in the study, and they were defined as eating meat at least weekly. Researchers, who identified 380 cases of colon cancer and 110 cases of rectal cancer among participants, said the non-vegetarians ate less meat than the average American.
The study underscores that advanced medical screening procedures such as the colonoscopy have saved many lives but it is even better to prevent cancer, potentially through diet.
The colorectal cancer report is part of Loma Linda University Health’s ongoing Adventist Health Studies, initiated in 1958 and among the world’s longest running research about health and longevity. Its previous findings have connected the Adventist diet to lower rates of obesity, diabetes, and high blood pressure.
“There’s a history going back to the 1950s of studies on Seventh-day Adventists, and most have found that they’re healthy, long-lived populations, so it’s interesting to probe and see why,” Orlich told The Wall Street Journal in discussing the latest cancer findings.
The Adventist Health Studies are also often discussed at healthcare seminars and conferences. CNN International television devoted a segment of its “Vital Signs with Dr. Sanjay Gupta” program to the research in February.
The Adventist Health Study-2 started in 2002 with funding from the National Cancer Institute, a U.S. government agency. In 2011, the National Cancer Institute awarded it a $5.5 million five-year grant to continue the research.