Cooked and cooled potatoes are a form of resistant starch, or RS for short. This is a type of starch that is not digested in the stomach or the small intestine, and it reaches the colon intact, this makes it a great prebiotic. As a prebiotic it falls into the category of an insoluble fiber, but unlike other insoluble fibers, which generally aren’t fermented much by the colonic bacteria, resistant starch is!
Several studies have looked at the impact of resistant starch on gut flora and health. Like other prebiotics, resistant starch selectively stimulates the growth of beneficial species like Bifidobacteria and Lactobacillus. It also increases the concentration of short-chain fatty acids like butyrate and propionate, and it’s been shown to protect against colon cancer, improve metabolic health, reduce fasting blood sugar and body weight, and improve insulin sensitivity. It is important to note that although it is a starch, it is not broken down into glucose and it never hits the bloodstream, therefore it will not affect your blood sugar.
Resistant starch can also help with sleep and mood, so anyone with insomnia, depression, or anxiety, can actually improve their symptoms with resistant starch, and that effect is possibly mediated via the gut-brain axis. Some studies have shown that high intake of resistant starch with no other fibers can actually decrease the diversity of beneficial bacteria species in the gut, which is definitely the opposite direction one would want to go, so resistant starch should always be part of a wider spectrum of fiber intake.
The easiest way to get resistant starch into your diet is to eat cooked and cooled potatoes, cooked and cooled rice, green bananas, green plantains and you can also supplement with green banana flour or green plantain flour as well as potato starch, from a good brand like Bob’s Red Mill. If you use a powder form, it can be added to your smoothie but remember to start small with the amount. Many times people who need prebiotics the most are the least likely to be able to tolerate them. So start slowly.