Reheating last night’s spaghetti may not sound like the most glamorous lunch suggestion, but consider it for your gut health. Why? It comes down to a process called starch retrogradation.
When carb-rich foods like pasta, potatoes, or rice are cooked and cooled, “the starch molecules reorganize into a more tightly packed, crystalline structure,” says Julie Pace, RDN, a dietitian specializing in women’s gut, hormone, and metabolic health. “This restructuring promotes the formation of resistant starch, which resists digestion in the small intestine and instead functions more like dietary fiber, helping to nourish beneficial gut bacteria.”
In other words, the resistant starch acts as a prebiotic, feeding the bacteria in your large intestine. “As these bacteria ferment resistant starch, they produce short-chain fatty acids, particularly butyrate,” Pace says. This nutrient “nourishes the cells lining the colon, helps maintain a healthy gut environment in which beneficial bacteria thrive, and has been associated with reduced gut inflammation and improved bowel regularity,” she adds.
According to The Johns Hopkins Patient Guide to Diabetes, other benefits of resistant starch include lower cholesterol levels, increased satiety, reduced blood sugar spikes, and a lower risk of colon cancer. For more on how to make the most of your carbs, keep scrolling.
How to transform your carbs into resistant starch
After cooking, Pace recommends allowing your carb of choice to chill in the refrigerator—make sure it’s set to 40 degrees Fahrenheit or below—for 12 to 24 hours to maximize resistant starch formation.
During this process, it’s important to prioritize food safety. “Never leave cooked food at room temperature for more than two hours, as harmful bacteria can multiply rapidly,” she says. “To cool starch safely, spread food in a shallow container no more than two inches deep and let the steam dissipate for about 15 to 30 minutes” before putting it in the fridge.
Then, enjoy within three to four days. “Some of my favorite ways to incorporate resistant starch are potato salad, pasta salad, or lentil salad,” Pace adds.
Do you have to eat it cold?
No, you can reheat the food once it’s completely cooled if that’s your preference. “Once resistant starch forms during cooling, much of it remains even after reheating,” Pace says. However, one exception to this could be russet potatoes; according to Johns Hopkins, their resistant starch content “may slightly decrease…after reheating.”
Are other nutrients affected by this process?
“Retrogradation primarily changes how starch is digested rather than the food’s overall nutrient content,” Pace says. “Protein, fat, vitamins, and minerals remain largely unchanged, although the cooking method itself can reduce some heat-sensitive and water-soluble vitamins.”
Are there naturally occurring sources of resistant starch?
Yes—lima beans, kidney beans, sourdough bread, unripe bananas, and plantains are some examples of foods that contain resistant starch, Harvard reports.
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