More than 130,000 men and women are told they have colon or rectal cancer (known collectively as colorectal cancer) every year, making it the third most commonly diagnosed cancer, according to the American Cancer Society.

But a new report from the American Institute for Cancer Research (AICR) and the World Cancer Research Fund (WCRF) provides new evidence that the right eating and exercise plan can really help lower your risk of developing the disease.

In the report, researchers analyzed 99 studies with data on 29 million people.

“The findings are clear that diet and lifestyle play a major role,” says lead author Edward L. Giovannucci, M.D., Sc.D., professor of nutrition and epidemiology at the Harvard TH Chan School of Public Health. “Despite it’s prevalence, colorectal cancer is a highly preventable disease.”  

Foods To Eat More Of

It’s long been suspected that eating more whole grains will reduce your risk of colon cancer, but this is the first time the AICR/WCRF has confirmed it.

“Until recently, there had not been many studies that directly examined whole grain intake and subsequent colorectal cancer risk in large populations,” says Giovannucci. “But now we have enough research to say the link has strong evidence.”

In fact, eating about three servings of whole grains a day can lower colorectal cancer risk by 17 percent. (One serving is equal to 1 cup of ready-to-eat cereal, a slice of bread, or ½ cup of cooked rice or pasta.)

Why do whole grains help?

“Fiber is one of the keys to prevention of colon cancer,” says Michael A. Valente, M.D., a colorectal surgeon at the Cleveland Clinic, who was not involved in the AICR/WCRF report. “But we suspect that it’s really the thousands of nutrients, minerals, and other natural chemical compounds present in foods that are high in fiber—such as whole grains and fruits and vegetables—that are helping to prevent cancer, not just the fiber itself.”

Many of these compounds have what the report called “plausible anti-carcinogenic properties.” Which is why, in addition to eating more whole grains, its smart to increase consumption of fiber-rich fruits and vegetables as well.  

Foods To Cut Back On

The researchers found that eating a lot of red meat (such as beef and pork) and processed meat (such as bacon, cold cuts, and sausage) were potentially harmful.

Every 1.8 ounces a day of processed meat increased risk by as much as 16 percent, while eating more than about 17½ ounces of red meat a week was labeled a “probable cause” of colorectal cancer.

One theory as to why these meats increase colon cancer risk is that they have high levels of heme iron, which has been shown to promote the growth of colorectal tumors.

The connection between alcohol and colorectal cancer was also “convincing,” according to the report, and was especially strong for those who drink more than 30 grams per day (the equivalent of about two glasses of wine, or two cocktails or two beers).

“If you do consume alcohol, keep your intake moderate,” recommends Giovannucci.  

Other Steps You Can Take

Getting more whole grains and veggies, and less meat may have another risk-reducing benefit: helping you to maintain a healthy weight. According to the report, there is strong, convincing evidence that people who are overweight are more likely to develop colon cancer.

All types of physical activity—not just formal exercise—was protective, too, with the most active people having about 20 percent lower risk of colon (but not rectal) cancer than the least active.

The report did not cover screening for colon cancer, but it's a preventive move that deserves mention. Colorectal cancer usually develops over 10 to 15 years without causing symptoms. Most cases start as noncancerous polyps in the lining of the large intestine or the rectum. Detecting and removing polyps prevents them from developing into cancer.

You should have a colonoscopy every five to 10 years staring at age 50.

And if you have a close relative who had colorectal cancer, you should be even more vigilant about changing your lifestyle and getting regular screenings.

“Having a first-degree relative (mother, father, sibling) with the disease increases your risk by nearly 100 percent compared to the average person,” says N. Jewel Samadder, M.D., a gastroenterologist at the Mayo Clinic and expert with the American Gastroenterological Association.

If that’s you, experts recommend that, in addition to improving your diet, weight, and activity level, you start getting colonoscopies at age 40.