FiberKit
Resistant starch
Starch that escapes digestion and feeds your gut bacteria, like fiber. Cooking starchy foods and then cooling them makes a little more of it.
Updated
What it is
Resistant starch is starch your small intestine can’t digest. It passes to your colon, where bacteria ferment it, as they do many fibers.
The five types
| Type | What it is |
|---|---|
| RS1 | Locked inside whole or coarsely ground grains |
| RS2 | Raw starch: raw potatoes, green bananas, high-amylose corn |
| RS3 | Starch that re-forms as cooked food cools, as in cooled potatoes and rice |
| RS4 | Chemically modified starch, made as a food ingredient |
| RS5 | Starch bound to fat, made as a food ingredient |
Cook, cool, then eat
When cooked starch cools, some of it re-forms into a structure your gut can’t digest. In one review, potatoes went from 0.8% to 1.6% resistant starch after cooling. In a rice study, white rice had 0.64 g per 100 g fresh, 1.30 g after cooling for 10 hours, and 1.65 g after a day in the fridge and reheating. So the gain is real but small, about a gram per 100 g.
Foods with resistant starch
Cooked beans, lentils and peas, and starchy foods that were cooked and cooled, are high in it: 5 to 15% of their dry weight, in one review. Green bananas and raw potato have the raw kind, RS2.
Questions
Which foods are high in resistant starch?
Cooked beans, lentils and peas, and starchy foods that were cooked and then cooled. One review puts them at 5 to 15% resistant starch by dry weight.
Does cooling rice increase resistant starch?
Yes, a little. In one study, white rice had 0.64 g per 100 g fresh and 1.30 g after cooling for 10 hours.
Does reheating destroy resistant starch?
Not all of it. In the same study, rice chilled for a day and then reheated had 1.65 g per 100 g, about 2½ times as much as fresh rice.
Are green bananas high in resistant starch?
Yes. Raw green bananas are a source of RS2, the kind found in raw starch.
Is resistant starch a fiber?
It acts like one: you don’t digest it, and bacteria in your colon ferment it. The FDA lets food makers count added high-amylose starch (RS2) as fiber on labels while it plans to add it to the official definition.
Sources
- Birt et al. (2013): Resistant starch: promise for improving human health. Advances in Nutrition
- Sonia et al. (2015): Effect of cooling of cooked white rice on resistant starch content and glycemic response. Asia Pacific Journal of Clinical Nutrition
- FDA (2018): Review of the scientific evidence on the physiological effects of certain non-digestible carbohydrates
- FDA: Questions and answers on dietary fiber
General information, not medical advice. If you have a health condition or take medicines, ask your doctor before adding a fiber supplement.