Cooling Rice Lowers Post-Meal Blood Sugar and Changes Starch Structure
Cooling cooked white rice before eating it alters its starch structure and lowers post-meal blood sugar spikes compared to eating the rice freshly cooked, according to clinical trials covered by outlets including Kyunghyang Shinmun. When rice cools, digestible starches transform into resistant starch, a form that resists breakdown in the small intestine and reaches the colon with properties similar to dietary fiber.
Starch Retrogradation Increases Resistant Starch Content
During cooking, rice starches absorb water and heat to swell and undergo gelatinization, making them easily accessible to digestive enzymes. As the cooked rice cools, a process called starch retrogradation causes starch molecules to realign into a more orderly structure. This structural shift increases the proportion of resistant starch.
Freshly cooked white rice contained 0.64 grams of resistant starch per 100 grams. Rice left to cool at room temperature for 10 hours raised that amount to 1.30 grams, while rice stored at 4 degrees Celsius for 24 hours and then reheated reached 1.65 grams.
Clinical Trials Confirm Lower Blood Sugar Responses in Healthy Adults
Participants who consumed rice that had been stored at 4 degrees Celsius for 24 hours and then reheated experienced significantly lower glycemic responses than those who ate freshly cooked rice.
The incremental area under the curve (AUC) measuring postprandial blood glucose was 152.0 for freshly cooked rice and dropped to 125.0 for the cooled and reheated rice, representing an approximate 18 percent decrease. Chemical analysis showed that much of the resistant starch created during the cooling phase remained intact even after the rice was reheated for consumption.
Type 1 Diabetes Patients Show Reduced Peak Blood Glucose
Participants consumed freshly cooked white rice alongside white rice that had been cooled at 4 degrees Celsius for 24 hours and reheated.
The cooling and reheating process lowered peak post-meal blood glucose from 11.0 mmol/L to 9.9 mmol/L, accompanied by a reduced glycemic response curve area. However, the Poznan researchers noted an increase in hypoglycemic episodes after consuming the cooled rice, indicating that patients managing type 1 diabetes may require adjustments to their insulin dosages when incorporating cooled and reheated starches into meals.
Evidence Remains Mixed Regarding Direct Weight Loss Effects
Whether resistant starch consumption directly reduces body weight remains inconclusive across existing scientific literature.
Conversely, appetite regulation studies show potential benefits regarding satiety. A meta-analysis of four randomized controlled trials published in Clinical Nutrition ESPEN in 2021 by researchers at Shoushtar Faculty of Medical Sciences in Iran observed lower subjective appetite scores among participants who consumed resistant starch compared to control groups.
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