What is Resistant Starch?
Super food for your digestive system!
Starchy foods like potatoes, corn and bananas can get a bad rap for having lots of calories with little nutritional value; however, nutrition science is proving differently. These foods are loaded with a valuable type of starch called resistant starch, which can provide significant gastrointestinal benefits.
Resistant starch resists digestion in the stomach and small intestine—hence, the name. This resistance is important. Since resistant starch isn’t broken down into sugar in the small intestine, it doesn’t spike blood sugar levels. Instead, it’s broken down in the large intestine where it feeds the good bacteria in the colon, creating beneficial molecules that promote a healthy gut.
Resistant starch may be helpful for ulcerative colitis and Crohn’s disease because of its beneficial effect on the colon’s microbiome. It has also been linked to the reduction of colon cancer, hemorrhoids, diverticulosis and constipation, as well as to better regulation of blood glucose and blood cholesterol.
While Americans eat plenty of starch, not all starches qualify as resistant starches. Foods that are high in resistant starch include potatoes, brown and white rice, beans and legumes, oats and whole-grain gluten-free pasta—all cooked and cooled.
This cooking-cooling prep is important. Cooking triggers the starch to absorb water and swell. As it cools, it crystallizes into a form that resists digestion. Think: cold potato salad, pasta salad, bean salad, hummus and bean dip.
Raw, unmodified potato starch is high in resistant starch, as are green banana flour and Hi-Maize flour. These powders can be added to water or milk of choice (cold or room temperature, not heated) or mixed into smoothies to get resistant starch benefits.
Good for Your Colon
Like valuable real estate, resistant starches are all about location, location, location. They travel unscathed through the small intestine to land in the large intestine (colon). There they are finally broken down.
“Unlike other forms of starches that are broken down by digestive enzymes in the small intestines, resistant starches actually resist digestion in the upper gastrointestinal tract,” explains Kate Scarlata, RDN, a digestive health expert in Boston.
When resistant starches reach the colon, they are fermented by bacteria, feeding the good bugs in the gut and producing important short-chain fatty acids, like butyrate. Studies show that butyrate suppresses inflammation in the colon—and more.
“Butyrate has been associated with numerous benefits for colon health, such as helping with motility, transporting fluids and healing inflammation, as well as lowering the risk of colon cancer,” Scarlata says.
Resistant starch may also reduce harmful gases in the gut (like hydrogen sulfide), which have been linked to inflammatory bowel diseases like ulcerative colitis.
Steady Blood Sugar
According to a recent study in the Journal of Nutrition, resistant starches have been shown to improve blood glucose levels and insulin control, important in warding off type 2 diabetes.
“Because resistant starches are not absorbed quickly by the intestines, they decrease spikes in insulin,” explains Edwin McDonald, MD, associate director of Adult Clinical Nutrition at The University of Chicago Medicine.
Keeping insulin levels in check helps ward off feelings of excessive hunger. And because resistant starch isn’t digested well, it doesn’t get converted to sugar. So it helps you feel full longer, reducing the tendency to overeat.
Resistant Starch in Foods
The average American is not eating enough resistant starch, studies show. The recommended amount for optimal health benefits is about 20 grams per day; Americans get only about 5 grams a day, according to the Journal of the American Dietetic Association.
Resistant starch is considered a prebiotic fiber (it helps feed probiotics, the good bacteria in your gut). When introducing any kind of fiber into your daily diet, a slow start is crucial. For best tolerance, begin with a small amount—for example, ¼ cup of lentils or kidney beans (soaked, cooked and cooled)—for the best tolerance. If too much resistant starch is ingested at first, it may cause bloating and flatulence in sensitive individuals.
“People with functional GI disorders, such as irritable bowel syndrome, will experience pain with too much fermentation in the colon,” McDonald says.
If there’s a lot of gas and bloating, GI experts usually err on the side of caution and recommend against increasing fiber or resistant starch. Consult with your healthcare practitioner or dietitian.
Victoria Shanta Retelny, RDN, is a lifestyle nutrition expert and author of Total Body Diet for Dummies. Follow her on Twitter @vsrnutrition.