But a recent study in Nature Communications shows that changing your diet can have an effect on health way sooner than you’d think: We’re talking just two weeks. That’s what researchers from University of Pittsburgh and Imperial College London found when they swapped the high-fat diet of 20 African Americans for the high-fiber diets of 20 rural South Africans. It took just 14 measly days for the high-fiber African diet to dramatically reduce markers for colon cancer risk in the Americans. And for the rural South Africans, two weeks on a high-fat American diet had an equal but opposite effect, greatly increasing chances for colon cancer. Why? Researchers credit these big benefits to dietary fiber, specifically a type of fiber called resistant starch, or RS. It’s found in high concentration in a corn porridge known as phutu—a staple of the rural South African diet—as well as in foods like oats, lentils, and unripe bananas. RS is not digested by the body, so it has no caloric value, and research has already linked it to lower colon cancer risks. MORE: 10 Cancer Symptoms Most People Ignore How can one starch have such a big effect? Researchers found that the high-RS African diet decreased cell multiplication in the colon, which makes the lining of the colon less vulnerable to environmental carcinogens. Plus, the African diet more than doubled the participants’ levels of butyrate, a natural byproduct produced by fiber breakdown that helps prevent cancerous masses from forming in the colon. MORE: This New Flour Cuts Calories By Over 25% To get the benefits observed in the study, lead author Stephen J.D. O’Keefe, professor of medicine at University of Pittsburgh, says you’d need to consume at least 50 grams of fiber a day. (The current government recommendation is 25 grams per day, and most Americans get only 15.) How can you get 50 grams of daily fiber? Easy! Start with a ½ cup bran cereal topped by 1 cup raspberries for breakfast, enjoy 1 cup of lentils in a soup or salad at lunch, add 2 tablespoons chia seeds to your afternoon smoothie (or to that lunch salad), and then aim to get 1 cup of green peas at dinner.
