Does refrigerating rice make it a resistant starch?

October 31, 2025 •

2 min read

According to a study published in the Asia Pacific Journal of Clinical Nutrition, cooked white rice cooled for 24 hours at 4°C significantly increased its resistant starch content and lowered the glycemic response in healthy subjects. This confirms that refrigerating rice does make it a resistant starch, offering a straightforward method to enhance its health benefits.

Quick Summary

Refrigerating cooked rice triggers a process called retrogradation, where starches recrystallize and become resistant to digestion. This increases the resistant starch content, which acts like fiber to benefit gut health and lower blood sugar spikes.

Key Points

Retrogradation: The cooling process of cooked rice causes starch molecules to re-crystallize, forming resistant starch.
Increased Resistant Starch: Refrigerating cooked rice for 12-24 hours can significantly increase its resistant starch (RS3) content, potentially by over double.
Lower Glycemic Index: The formation of resistant starch slows the release of glucose into the bloodstream, resulting in a lower and more stable blood sugar response.
Supports Gut Health: Resistant starch functions as a prebiotic fiber, nourishing beneficial gut bacteria and contributing to improved digestive health.
Enhances Satiety: Like other fibers, resistant starch can increase feelings of fullness, which may assist with appetite control and weight management.
Requires Safe Handling: To prevent food poisoning from Bacillus cereus, cooked rice must be cooled rapidly (within one hour) and refrigerated promptly.
Reheating is Safe: The resistant starch formed remains largely intact even after reheating, provided the rice was stored correctly and is heated thoroughly.

The Science Behind Starch Retrogradation

When rice is cooked, the starches gelatinize, becoming easy to digest. Cooling cooked rice, however, leads to retrogradation, where starch molecules, particularly amylose, re-form into a structure that resists digestion. This is Type 3 resistant starch (RS3). Reheating doesn't completely reverse this effect.

Gelatinization and Retrogradation

Gelatinization makes starches digestible. Retrogradation, induced by cooling, makes them resistant by creating a more crystalline structure.

What Happens to Your Body

The resistant starch created by cooling rice offers several health benefits.

Improved Glycemic Response

Resistant starch isn't digested in the small intestine, slowing sugar release into the bloodstream and resulting in lower blood sugar spikes compared to freshly cooked rice.

Enhanced Gut Health

Passing to the large intestine, resistant starch acts as a prebiotic, feeding beneficial gut bacteria. This fermentation produces short-chain fatty acids like butyrate, supporting gut health.

Increased Satiety

Like other fibers, resistant starch can increase feelings of fullness, potentially aiding weight management.

Critical Food Safety Considerations

Proper handling of cooked rice is essential to avoid food poisoning from Bacillus cereus spores.

To ensure safety, follow these steps:

Cool rice within one hour.
Spread it thinly to speed cooling.
Refrigerate in an airtight container at or below 4°C.
Use within 24-48 hours.
Reheat thoroughly and only once.

Maximizing Resistant Starch Formation

Simple refrigeration works, but these methods can enhance resistant starch production:

Adding healthy fat during cooking may increase resistant starch upon cooling.
Cooling longer than 12-24 hours might slightly increase resistant starch.
Using rice varieties high in amylose yields more resistant starch.

Comparison: Freshly Cooked vs. Refrigerated Rice


Feature	Freshly Cooked Rice	Refrigerated Rice (Cooled 12+ hours)
Starch Type	Easily digestible starch (gelatinized)	Contains a higher proportion of resistant starch (retrograded)
Glycemic Index	Higher	Lower
Digestion Speed	Faster, leading to quicker sugar absorption	Slower, leading to a more gradual sugar release
Nutritional Profile	Rapidly absorbed carbohydrates	Carbohydrates with fiber-like properties
Gut Health	Minimal prebiotic effect	Acts as a prebiotic, feeding beneficial bacteria
Blood Sugar Impact	Higher spike	Lower, more stable response

Conclusion

Refrigerating cooked rice effectively increases resistant starch, offering benefits like improved blood sugar control and gut health. This transformation through retrogradation creates a more fibrous carbohydrate that acts as a prebiotic. Following strict food safety guidelines for cooling and storage allows you to safely enjoy leftover rice and its nutritional advantages. This simple method enhances a staple food for better metabolic and digestive health. For more detailed information on resistant starch, consult resources like CSIRO.

Frequently Asked Questions

To maximize the formation of resistant starch, cooked rice should be refrigerated for at least 12 hours, with some studies showing optimal results after 24 hours at around 4°C.

No, reheating does not eliminate the resistant starch. The retrograded starch structure is stable enough to maintain its resistance to digestion even after being warmed up, though a small amount may be lost.

Yes, it is safe to eat cold, leftover rice if it was cooled down rapidly and refrigerated properly. The main safety risk is from the Bacillus cereus bacteria, which multiplies when rice is left at room temperature for extended periods. Cool rice within one hour and consume within 24-48 hours.

Yes, the process of cooking and cooling also works for other starchy foods, such as pasta, potatoes, and beans, to increase their resistant starch content.

One of the most significant health benefits is the prebiotic effect on your gut. As it ferments in the large intestine, it produces beneficial short-chain fatty acids like butyrate, which support a healthy gut lining and reduce inflammation.

Yes, the amount of amylose in the rice can influence resistant starch formation. Varieties with a higher amylose content tend to produce more resistant starch upon cooling than those with less.

To cool rice quickly, spread it out in a thin, even layer on a baking sheet or shallow dish. This allows the heat to dissipate rapidly, bringing the temperature down to a safe level for refrigeration within an hour.