Resistant starch (RS) is a type of dietary fiber which you can’t digest but your gut flora can and is naturally found in many carbohydrate-rich foods such as potatoes, grains, brown rice, and beans, particularly when these foods are cooled.
What makes a starch “resistant”?
This type of fiber resists breakdown in the small intestine and stomach and makes it through to the large intestine intact. Therefore, resistant starch is so named because it resists digestion.
Once it reaches the large intestine, RS acts as food for your gut flora. The gut flora ferments it into short-chain fatty acids – scfa, such as – butyrate, acetate, and propionate. According to recent studies, RS appears to increase butyrate production more when compared with other soluble fibers.
Butyrate also acts as a potent anti-inflammatory agent for the colonic cells and functions to improve the integrity of our gut by decreasing intestinal permeability, hence, butyrate keeps toxins in the gut and out of the bloodstream.
There are four different types of RS:
- It is found in seeds, grains, and legumes and resists digestion because it is bound within the fibrous cell walls.
- It is intrinsically indigestible in the raw state due to its high amylose (a type of polymer found in starch) content. This type of RS is found in potatoes, green (unripe) bananas, plantains, and it becomes accessible upon heating.
- It is formed when certain starchy foods, including potatoes, rice, and some types of bread are cooked and then cooled. The cooling process turns some of the digestible starches into RS via a process called retrogradation.
- It doesn’t occur naturally and has been chemically modified; usually found in “hi-maize resistant starch.” They are said to be less digestible in vitro.
Health benefits of resistant starch
Better satiety – RS is bulky, so it takes up space in your digestive system. Plus, because you can’t digest or absorb it, RS never enters your bloodstream and slows a number of nutrients released into the bloodstream, which keeps appetite stable.
Weight loss – adding resistant starch to meals increases feelings of fullness and makes people eat fewer calories. Furthermore, one study found that replacing just 5% of the day’s carbohydrates with a source of RS can boost post-meal fat burn by up to 30%.
Cancer prevention – it is also linked with decreased risk of colorectal cancer, thought to occur through a few different mechanisms, such as – favorable changes in gene expression, protection from DNA damage, and increased apoptosis of cancerous or pre-cancerous cells.
Improves insulin sensitivity – a few studies concluded that RS can improve insulin sensitivity, as in how well the body’s cells respond to insulin. Moreover, consumption of RS has a “second meal effect” – meaning that if you eat RS with breakfast, it will also lower the blood sugar spike at lunch.
Improves magnesium absorption – most likely because it improves gut integrity and function, RS increases dietary magnesium absorption.
Improves your gut flora – it feeds the bacteria living in your gut which is accountable for breaking down solids into nutrients your body can use.
Here is a list of 7 foods that are high in resistant starch:
Lentils are one of the best sources of RS. According to scientists at the University of Illinois, about 25.4% of the starch in cooked lentils is RS and that nearly 48% of this RS reaches the colon intact.
Chickpeas, like other legumes, are perhaps one of the best food sources of RS and slowly-digested carbohydrate. They are also a good source of protein and folate. Folate is a water-soluble B9 vitamin that occurs naturally in food, which may help to reduce your risk of colorectal cancer.
If prepared correctly and left to cool, potatoes are an important source of RS. Actually, a study by the European Journal of Clinical Nutrition established a 57% increase in RS after refrigerating their spuds for 24 hours.
It is the favored RS source for adults living with type 2 diabetes mellitus. Although corn is commonly grouped together with other grains and used in almost identical methods, it’s actually not a “grain” and doesn’t contain any gluten.
Dry oatmeal is 11 percent RS. Moreover, antioxidant compounds unique to oats, called avenanthramides, help prevent free radicals from damaging the arteries, hence reducing the risk of cardiovascular disease, according to a study published in The Journal of Nutrition and conducted at Tufts University.
#6 Brown Rice
The amount of RS in rice is influenced by the cooking method and rice variety. Brown (unmilled) rice is gaining popularity due to its naturally occurring mineral and vitamin content, and higher dietary fiber, compared with white rice.
#7 Under-ripe bananas
A large raw under-ripe (green) banana will provide you with 5.44 grams of RS. In addition, bananas contain inulin, a RS that serves as a strong probiotic promoting healthy gut flora as well as helping to control blood sugar.
References https://www.ncbi.nlm.nih.gov/pubmed/15287677 http://ajcn.nutrition.org/content/73/2/415s.full https://www.ncbi.nlm.nih.gov/pubmed/24228189