A study has linked a vegetarian diet to a lowered risk of colorectal cancers when compared to data on nonvegetarians, researchers are reporting.
An emphasis on screening tests has gone a long way in battling colorectal cancers -- the second leading cause of cancer deaths in the U.S. following lung cancer -- but primary prevention through the lowering of risk factors is still seen as a vital consideration, experts say.
In a study by Michael J. Orlich of Loma Linda University in California, Orlich and his research colleagues identified 380 cases of colon cancer and 110 cases of rectal cancer in 77,659 study participants.
An analysis of the dietary habits of the participants showed that, compared with nonvegetarians, those on a vegetarian diet had a had an average 22 percent lower risk for all colorectal cancers, broken down as a 19 percent lower risk for colon cancer and 29 percent lower risk for rectal cancer.
"Our vegetarians not only ate less meat than the non-vegetarians, but also less sweets, snack foods, refined grains and caloric beverages," Orlich says, noting that in addition they consumed more fruits, vegetables, whole grains, nuts and beans.
Previous studies have linked red meat and processed meats to elevated risks of colorectal cancer, he says.
Although studies including Orlich's have shown an association between a vegetarian diet and a lowered risk of colon cancer, it is unknown what the causal relationship might be, if one even exists, experts say.
It is not certain whether there is some protective quality in vegetables or whether there are more harmful qualities in meat, says Dr. Alfred Neugut, an epidemiology professor at Columbia University Medical Center in New York City.
One unexpected finding is that risk factors are even lower for those vegetarians who include fish and seafood in their diets.
"We were surprised to find that pescovegetarians had a significantly lower risk of colorectal cancers than people on other vegetarian diets," Olich notes.
Pescovegetarians who ate fish at least once a month and meat less than once a month, had the biggest risk reduction of 43 percent, the researchers found.
In comparison, lacto-ovo vegetarians who consumed eggs and dairy while limiting fish and meat to less than once a month saw a risk reduction of 18 percent, while vegans who ate eggs, dairy, fish, and meat less than once a month had a 16 percent reduction in colorectal cancer risk.
"The comforting takeaway is that a person doesn't need to be vegan and cut out all eggs, dairy, and fish to get some benefit in terms of reducing the risk of cancer," says Dr. Leonard Saltz, chief of the gastrointestinal oncology service at Memorial Sloan Kettering Cancer Center in New York.