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Does resistant starch impact the poop of healthy adults?

If you've ever eaten a potato that's been cooked and refrigerated, then reheated, you've eaten resistant starch. Aside from impacting your gut bacteia, will this starch affect your poop?

Study under review: Positive effects of resistant starch supplementation on bowel function in healthy adults: a systematic review and meta-analysis of randomized controlled trials


Resistant starch has become a popular topic over the last decade for its proposed health benefits as a fiber and for its potential as a functional food ingredient. As the name alludes, resistant starch is defined as a portion of starch that cannot be digested by human enzymes (it resists digestion), instead entering the large intestine to feed the microbiome.

There are currently five known types of resistant starch (shown in Table 1), which are briefly summarized in the table below and addressed in more detail in the FAQ section. All resistant starches act as a prebiotic fiber (which feeds the microbiome) and have been shown to facilitate a diverse and healthy microbiome. Additionally, resistant starch has been shown to increase the production of short-chain fatty acids within the colon, which may have anti-cancer effects and promote the growth of healthy colon tissue.

Table 1: Types of resistant starch
Designation Description Example
Resistant starch type-I Physically inaccessible starch Coarsely ground or whole-kernel cereal grains
Resistant starch type-II Native (uncooked) amylose starch Raw potatoes or green bananas
Resistant starch type-III Retrograde starch Cooked and cooled starchy foods such as potatoes or rice
Resistant starch type-IV Chemically modified starch Various synthetic starches; not found in nature
Resistant starch type-V Amylose-lipid complex High-amylose starches cooked in the presence of fat, such as stir-fried rice

Composition, consistency, frequency, and weight of bowel movements have been proposed as key indicators of bowel function and digestive health. Despite a logical basis to suggest that consuming resistant starch would benefit bowel function, data from healthy humans is scarce and conflicting. For instance, two studies[1] have shown that resistant starch supplementation significantly increases fecal weight while another[2] reported a non-significant decrease.

To consolidate the currently available evidence, the current study performed a meta-analysis investigating how resistant starch supplementation affects bowel function in healthy adults.

Resistant starch is a type of fiber that has been suggested to have numerous health benefits for the gut and systemically. The current study was a meta-analysis of human trials investigating how resistant starch supplementation impacted bowel function.

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