Whole Grains Wage War Against Cancer

A landslide of health benefits are linked with eating whole grains. One in particular is whole grains’ potential for fending off cancer, a disease that touches more than 11 million Americans. FDA has backed up whole grains’ cancer-fighting status with an approved health claim, “Diets rich in whole-grain foods and other plant foods and low in total fat, saturated fat and cholesterol may reduce the risk of heart disease and some cancers.”

Although studies have linked whole grains with protection against many types of cancer—colorectal, gastric, mouth and throat, digestive tract, hormone-related, pancreatic, and endometrial—it’s colorectal cancer that catches the spotlight. A recent expert report from the American Institute for Cancer Research, Washington, D.C., “Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective,” found probable evidence that foods containing dietary fiber, such as whole grains, can decrease the risk of developing colorectal cancer. In a May 2007 study in the AmericanJournal of Clinical Nutrition (85(5):1,353-1,360), researchers studied data for nearly half a million middle-aged men and women enrolled in the NIH-AARP Diet and Health Study, and discovered grain fiber as well as whole grains were likely to reduce the risk of colorectal cancer.

The whole package

Whole grain’s isolated constituents, such as dietary fiber, vitamins, minerals and plant compounds, do not fully explain the cancer-preventive effects, leading scientists to believe that the unique nutrients found in whole grains provides a “package” for delivering cancer protection. Whole grains may fight cancer through many mechanisms, including large-bowel effects, antioxidant activity, alterations in blood glucose levels, weight loss, hormonal effects and the power of biologically active compounds.

Whole grains are chock full of fermentable carbohydrates, such as dietary fiber, resistant starch and oligosaccharides. These undigested carbohydrates increase fecal weight, speed transit time and are fermented in the colon by intestinal microflora into short-chain fatty acids that are linked to lower cancer risk.

Researchers increasingly suspect insulin may play a role in cancer. Colon-cancer incidence has been linked to higher levels of blood glucose, insulin and body weight. Since food structure is more significant to glycemic response than dietary-fiber content, it makes sense that whole grains produce a lower glycemic response than refined grains. When comparing plasma insulin response in grains, a stepwise effect has been observed, with increases in insulin response as the grain is more refined: whole grains less than cracked grains less than coarse flour less than fine flour.

Whole grains’ abundant antioxidants may work to prevent cancer, protecting DNA from oxidative stress, damage and mutation that can lead to cancer. In the mix are soluble antioxidants, including phenolic acids, flavonoids, tocopherols and avenanthramides. Largely, insoluble antioxidants are bound as cinnamic acid esters to arabinoxylan side chains of hemicellulose. Insoluble grain fiber also possesses antioxidant activity—in the colon, enzymes free the bound phenolic acids so that cells may absorb it to gain antioxidant protection and enter the circulation. Thus, whole grains provide antioxidant protection over a long period through the entire digestive tract. Vitamin E also acts as a powerful antioxidant, and selenium functions as a cofactor for glutathione peroxidase, an enzyme that protects against oxidative tissue damage and suppresses cell proliferation.