Starchy foods get a bad rap. White bread and potatoes are devoid of nutrients, critics say, while the Paleo crowd eschews legumes and grains as unnecessary for the "ideal" human diet. But resistant starches—which act more like fiber in the body—are really quite good for you. In fact, one health benefit may be of particular significance to those Paleo adherants: Eating resistant starches, says a new study, may help reduce the risk of colorectal cancer associated with diets high in red meat.
Resistant starch get its name because it resists digestion in the small intestine and passes through to the colon, where it produces short-term fatty acids that aid digestion and reduce inflammation, says Frances Largeman-Roth, R.D. Examples of resistant starches include underripe (still slightly green) bananas; cooked and cooled pasta and potatoes (think pasta or potato salad); raw potato starch; and yes, those Paleo no-no's: oats, barley, beans, and lentils.
The fiber-like starch has other benefits, as well: "It helps you feel full, and therefore is a great weight-loss tool," explains Largeman-Roth, who also authored Eating in Color and co-authored The CarbLovers Diet, which is based on the science of resistant starches. "Most people only eat 5 grams a day, but we should be eating more like 10 to 15 grams to get these benefits."
Most recently, resistant starch has been in the news because of a study published in this month's Cancer Prevention Research. When Australian researchers put volunteers on highly carnivorous diets (300 grams a day of lean red meat) and gave half of them 40 grams a day of resistant starch powder, they discovered that the starch had a protective effect: The red-meat-only group saw a 30 percent increase in cancer-promoting molecules in their bowels, while the meat-plus-starch group's levels did not change. (Again: Paleo people, take note.)
"Our study supports the existing evidence that a balanced diet containing plenty of whole grains, legumes, fruits, and vegetables is likely to be beneficial for bowel health," says study co-author Karen Humphreys, Ph.D. "More specifically, incorporating foods that are high in resistant starch and/or dietary fiber appear to ameliorate the damaging effects of a diet high in red meat."
Of course, meat-heavy diets have been linked to other health conditions besides just colorectal cancer—so limiting your servings and keeping portion sizes small (3 to 5 ounces) are still smart moves, says Largeman-Roth, resistant starches or not. "So is including plenty of fruits and vegetables, which have been shown to reduce the risk of heart disease, obesity, and certain cancers," she adds.
Bottom line: Resistant starch can help keep you full and maybe even reduce your cancer risk. Aim for at least 10 to 15 grams in your daily diet (a medium-size banana contains about 5 grams; 12.5 grams if it's slightly unripe), especially if you eat a lot of red meat.
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