The effect of eating cooked and cooled potato on gut microbiota Original paper

Resistant starch (RS), a type of carbohydrate that resists digestion in the small intestine, acts as a prebiotic in the large intestine, thus supporting beneficial gut bacteria like those that produce short-chain fatty acids (SCFAs) such as butyrate. Resistant starch is found in a number of foods, including whole grains and green bananas, and in rice and potatoes that have been cooked and cooled (the RS forms on cooling and remains even after reheating). Could adding potato to the diet in place of refined grains affect the gut microbiota and/or increase fecal SCFAs?

This randomized crossover trial recruited 50 adults, who were randomized into two groups. The participants were given daily prepared and cooled/frozen side dishes: 4 weeks of either potato or refined-grain dishes, followed by a washout period of 2–3 weeks, then 4 weeks of the other dish. The amount of RS was quantified in the prepared side dishes. Fecal samples were collected from each participant at baseline and after 2 and 4 weeks of each dish.

There was considerable overlap in the amount of RS in the potato and grain dishes, but the potato dishes provided an average of 1.74 grams more RS per day than the grain dishes. However, despite a modest increase in RS consumption, there was no significant difference in SCFA between groups and no significant change from baseline.

Gut microbiome alpha-diversity (within-sample species diversity) was slightly but significantly lower during potato dish consumption than during refined-grain dish consumption; however, neither was significantly different from baseline. There were no significant differences or changes in beta-diversity (between-sample species diversity). Fecal samples collected during the potato-dish consumption had significantly higher abundance of two bacterial species, Hungatella xylanolytica (aka Bacteroides xylanolyticus) and Roseburia faecis, a butyrate-producing species.