The Cold Truth: Does Rice in the Fridge Lower the Glycemic Index?

November 1, 2025 •

3 min read

According to a 2015 randomized controlled trial, cooling cooked white rice in the refrigerator for 24 hours can significantly increase its resistant starch content. This molecular change directly addresses the question of does rice in the fridge lower the glycemic index?, offering a simple dietary strategy with notable health benefits.

Quick Summary

The process of cooling cooked rice increases its resistant starch content through retrogradation, which slows digestion and glucose absorption. This results in a lower glycemic index and a more stable blood sugar response, a beneficial hack for managing carbohydrate intake, particularly for diabetics.

Key Points

Resistant Starch Formation: Cooling cooked rice triggers a process called retrogradation, which increases its resistant starch (RS) content.
Lowered Glycemic Index: The increased resistant starch makes the rice harder to digest, resulting in a slower release of glucose and a lower glycemic index.
Better Blood Sugar Control: This leads to smaller, more stable blood sugar spikes, which is especially beneficial for people with diabetes.
Reheating Retains Benefits: Reheating the cooled rice does not destroy the resistant starch, so you can still enjoy it warm while reaping the health benefits.
Improved Gut Health: Resistant starch acts as a prebiotic fiber, feeding beneficial gut bacteria and promoting a healthy digestive system.
Food Safety is Crucial: To prevent bacterial growth, cooked rice must be cooled quickly and refrigerated properly before being reheated thoroughly.
Satiety and Weight Management: The slow digestion of resistant starch can increase feelings of fullness, potentially aiding in weight control.

The Science Behind the Starch: Retrogradation Explained

Rice contains two main starches: amylose and amylopectin. Cooking rice gelatinizes these starches, making them easy to digest and causing blood sugar spikes. However, cooling cooked rice triggers starch retrogradation, where the starch molecules re-crystallize into a form less digestible by enzymes in the small intestine. This new structure, Type 3 resistant starch (RS3), acts like dietary fiber, passing to the large intestine undigested. This slows carbohydrate digestion and absorption, leading to a more gradual rise in blood glucose. Reheating cooled rice retains most of this resistant starch and its benefits.

How a Lower Glycemic Index Benefits Your Body

Consuming foods with a lower glycemic index (GI), such as cooled rice, can improve blood sugar control by preventing rapid glucose spikes. This can be especially helpful for individuals managing diabetes and may improve insulin sensitivity. The resistant starch in cooled rice also acts as a prebiotic, nourishing beneficial gut bacteria. These bacteria produce short-chain fatty acids like butyrate, which support gut health. A healthy gut can also contribute to reduced inflammation and a stronger immune system. Additionally, resistant starch can increase feelings of fullness, potentially aiding weight management.

Comparison of Rice Preparation Methods


Preparation Method	Glycemic Impact	Resistant Starch Content	Digestibility	Benefits
Freshly Cooked Rice	High GI	Low	Rapid	Immediate energy release
Refrigerated Rice (Eaten Cold)	Lower GI	High	Slow	Stable blood sugar, gut health, satiety
Refrigerated & Reheated Rice	Lower GI	High	Slow	Retains most benefits of cooled rice, versatile for meals
Parboiled & Cooled	Lowest GI	Very High	Very Slow	Maximum blood sugar control and gut health

Maximizing the Resistant Starch in Your Rice

To enhance resistant starch formation in rice:

Cool for 24 Hours: Chilling at 4°C (39°F) for 24 hours is optimal.
Reheating Method: Gentle reheating, such as microwaving on a lower setting, helps preserve the resistant starch structure.
Add Coconut Oil: Adding a teaspoon of coconut oil during cooking may further reduce the glycemic response after cooling.
Use Basmati Rice: Basmati rice naturally has higher amylose, leading to more resistant starch upon cooling.
Combine with Fiber and Protein: Eating cooled rice with protein and fibrous vegetables can improve blood sugar regulation.

Important Safety Precautions

Proper handling of cooked rice is essential to prevent food poisoning from Bacillus cereus bacteria. To minimize risk:

Cool Quickly: Cool cooked rice within an hour.
Refrigerate Promptly: Store in an airtight container in the refrigerator and use within a few days.
Reheat Thoroughly: Ensure reheated rice is steaming hot.

A Simple Strategy for Better Nutrition

Adding cooled and reheated rice to your diet is an easy way to enjoy rice while managing its blood sugar impact and increasing beneficial resistant starch. This method offers flexibility for various meals and can be a good source of fiber. While individual results may vary, the science supports its benefits for blood sugar and gut health.

Conclusion: A Simple Strategy for Better Nutrition

Cooling cooked rice in the fridge does lower its glycemic index. This process of retrogradation increases resistant starch, slowing digestion and resulting in a more moderate blood sugar response. The added resistant starch also benefits gut health by acting as a prebiotic. This simple trick can be a valuable addition to a health-conscious diet, especially for those managing blood sugar. It is always advisable to consult a healthcare provider regarding dietary changes. For further information on resistant starch, you can refer to an article from NIH.

Frequently Asked Questions

Chilling cooked rice for at least 16-24 hours in the refrigerator is recommended for a significant increase in resistant starch content.

No, reheating does not negate the increase in resistant starch. The beneficial molecular structure is retained, allowing you to enjoy the lower glycemic index even when the rice is warm.

Cooling rice is safe if done correctly. Quickly cool and refrigerate cooked rice within one hour to prevent bacterial growth. Reheat thoroughly until steaming hot.

Yes, long-grain varieties like Basmati, with higher amylose content, tend to form more resistant starch upon cooling compared to short-grain varieties.

Yes, the process of cooking and cooling also increases the resistant starch content and lowers the glycemic index of other starchy foods like pasta and potatoes.

Initially, increasing resistant starch intake may cause mild gas or bloating as the gut adjusts. Introducing it gradually can help minimize these effects.

Resistant starch is a prebiotic that feeds beneficial gut bacteria in the large intestine. This fermentation produces short-chain fatty acids, like butyrate, which support colon cell health and a healthy gut environment.