Does Reheating Rice Destroy Resistant Starch? The Surprising Truth

November 2, 2025 •

4 min read

A 2015 study comparing different preparations of cooked white rice found that rice cooled and then reheated had 2.5 times the resistant starch of freshly cooked rice. This debunks the common misconception, but does reheating rice destroy resistant starch, or is the benefit retained even after warming it up?

Quick Summary

Reheating cooked and cooled rice does not destroy resistant starch; in fact, the process of cooling and subsequent reheating can increase its content. This occurs due to starch retrogradation, offering benefits like improved blood sugar control and gut health.

Key Points

Reheating Preserves Resistant Starch: Reheating rice that has been cooked and cooled does not destroy the beneficial resistant starch that formed during the cooling process.
Cooling is Key for Formation: The crucial step for increasing resistant starch in rice is refrigerating it after cooking, which triggers the process of retrogradation.
Potential for Further Increase: Some studies show that microwave reheating can actually increase the rice's resistance to digestion even further, enhancing the health benefits.
Reduces Blood Sugar Spikes: Eating cooled and reheated rice results in a lower blood sugar response compared to eating it freshly cooked.
Supports Gut Health: As a type of fiber, resistant starch feeds beneficial gut bacteria, promoting the production of short-chain fatty acids like butyrate.
Food Safety is Paramount: To avoid the risk of food poisoning from Bacillus cereus, always cool cooked rice quickly and refrigerate it properly.

The Science Behind Resistant Starch

Resistant starch (RS) is a type of carbohydrate that resists digestion in the small intestine, acting more like soluble fiber in the body. Instead of being broken down into glucose and absorbed, it travels to the large intestine where it is fermented by beneficial gut bacteria. This process produces short-chain fatty acids (SCFAs), such as butyrate, which are crucial for colon health and offer systemic benefits, including improved insulin sensitivity. Starch that is highly digestible, known as rapidly digestible starch (RDS), is what causes rapid spikes in blood sugar. The goal of increasing resistant starch is to reduce the amount of RDS and increase the portion of starch that benefits the gut microbiome.

How Resistant Starch is Formed in Rice

The resistant starch type relevant to cooked rice is Type 3, also called retrograded starch. This forms through a process called retrogradation, which occurs when starchy foods are cooked and then cooled. Cooking rice causes the starch granules to absorb water and swell, a process known as gelatinization. When this gelatinized starch cools, the molecular chains (specifically amylose) rearrange and re-associate into a more compact, crystal-like structure. This retrograded starch is less accessible to digestive enzymes in the small intestine, making it "resistant" to digestion. The longer the cooling period, typically 12 to 24 hours in the refrigerator, the more resistant starch is formed. Some studies also indicate that repeated heating and cooling can further enhance resistant starch levels.

The Effect of Reheating on Resistant Starch

Contrary to the myth that reheating destroys the beneficial resistant starch, research shows that the retrograded starch is surprisingly heat-resistant. A key study published in the Asia Pacific Journal of Clinical Nutrition found that reheated rice, after being cooked and cooled, had a significantly higher resistant starch content than freshly cooked rice. The reheating process itself—particularly with a microwave—can even contribute to the formation of more resistant starch under certain conditions. Microwave reheating has been shown to increase the digestion resistance of cooked rice, leading to a higher resistant starch content, especially when the rice is reheated after cold storage.

Microwave Reheating and Digestion Resistance

Research has explored how microwave reheating affects rice that has been refrigerated after cooking. One study revealed that microwave reheating can increase the proportion of V-type crystallites, a form of retrograded starch that is less digestible. This suggests that reheating doesn't just preserve the resistant starch formed during cooling, but can actually make the starch even less susceptible to enzymatic breakdown. For those managing blood sugar, this is excellent news, as the cooled and reheated rice results in a lower glycemic response compared to eating fresh rice. For more scientific details, see this publication on ScienceDirect.

How to Maximize Resistant Starch in Rice Safely

To increase resistant starch in your leftover rice, follow these simple steps while prioritizing food safety to prevent the growth of Bacillus cereus, a common food-poisoning bacteria associated with improperly stored rice:

Cool Quickly: After cooking, spread the rice on a shallow plate or baking sheet to cool it down as rapidly as possible. Do not leave cooked rice at room temperature for more than two hours.
Refrigerate: Transfer the quickly cooled rice into an airtight container and refrigerate for at least 12-24 hours. The cooling process is crucial for retrogradation to occur.
Reheat Thoroughly: When ready to eat, reheat the rice until it reaches an internal temperature of 165°F (74°C). Microwave heating has been shown to be effective, but any method that heats the rice through completely will work.

Benefits Beyond Blood Sugar

The advantages of increasing resistant starch go beyond lowering the glycemic response. The fermentation in the large intestine acts as a prebiotic, nourishing the gut microbiome. This can improve overall digestive health, help reduce inflammation, and even improve mineral absorption. Furthermore, because resistant starch has fewer calories per gram than regular starch (2 vs 4), it can contribute to weight management by increasing feelings of fullness and reducing overall caloric intake.

Comparison of Rice Preparations


Preparation	Resistant Starch Content	Glycemic Response	Digestibility	Key Feature
Freshly Cooked	Low	High	Rapid	Easily digested, provides quick energy
Cooled Only	Increased	Lower	Slower	Formed through retrogradation, beneficial gut food
Cooled & Reheated	Increased (potentially higher)	Lower	Slower	Retains and may enhance RS, offers convenience and health benefits

Conclusion

The notion that reheating rice destroys resistant starch is a myth. In fact, the controlled cooling and subsequent reheating of cooked rice is an effective and proven method for significantly increasing its resistant starch content. This offers a simple dietary strategy to enjoy rice with added health benefits, including better blood sugar management and improved gut health. By following proper food safety protocols, you can confidently prepare, cool, and reheat your rice to harness these nutritional advantages without compromising flavor or safety.

Frequently Asked Questions

Resistant starch is a type of carbohydrate that bypasses digestion in the small intestine. It acts as a prebiotic, feeding the good bacteria in your colon, which in turn produce beneficial short-chain fatty acids that improve gut health and insulin sensitivity.

The process involves starch retrogradation. Cooking gelatinizes the starch, and as the rice cools, the starch molecules re-crystallize into a structure that is more resistant to digestive enzymes. This process is most effective when refrigerated for 12-24 hours.

Yes, eating cooled and reheated rice leads to a lower blood glucose response compared to eating it freshly cooked. This is because the reheating process does not significantly alter the resistant starch formed during cooling.

Some studies suggest that repeated cooking and cooling cycles can modestly increase resistant starch levels. However, it's important to be mindful of food safety and not to push the process excessively, as benefits might plateau after a few cycles.

Yes, but proper food safety is critical. Cooked rice should be cooled quickly, refrigerated within two hours, and reheated thoroughly to a temperature of 165°F (74°C) to kill any potential Bacillus cereus bacteria.

Microwave reheating, in particular, has been shown to increase the digestion resistance of cooled rice, potentially boosting the final resistant starch content. Other reheating methods do not appear to destroy the existing resistant starch either, but may not offer the same potential boost.

While the process applies to most rice varieties, the potential for resistant starch formation is influenced by the rice's amylose content. Rice varieties with higher amylose content, like long-grain rice, tend to form more resistant starch during cooling.

Yes, the process of cooling and reheating also works for other starchy foods such as pasta, potatoes, and legumes. This retrogradation effect is not unique to rice.