Does Refrigerating Potatoes Lower Carbs? Unpacking the Science of Resistant Starch

October 5, 2025 •

3 min read

According to a study published in the Journal of Medicinal Food, cooling cooked potatoes can significantly lower their glycemic index. This phenomenon has led many to wonder: does refrigerating potatoes lower carbs? The answer involves a fascinating process that converts some of the potato's digestible starch into a healthier, fiber-like substance.

Quick Summary

Cooling cooked potatoes converts some starches into resistant starch through a process called retrogradation. This decreases the amount of digestible carbohydrate, which can improve gut health and blood sugar control.

Key Points

Resistant Starch is Key: Cooling cooked potatoes induces a chemical change called retrogradation, converting some digestible starch into resistant starch.
Fewer Available Carbs: As resistant starch is not easily digested, the amount of carbs that the body can readily absorb is reduced.
Improves Gut Health: Resistant starch acts as a prebiotic, feeding the beneficial bacteria in your gut microbiome.
Lowers Glycemic Index: Cooled potatoes have a lower glycemic index, leading to a smaller and more stable rise in blood sugar levels.
Reheating is Okay: You can reheat the potatoes after they have been cooled, and they will largely retain their increased resistant starch content.
Maximize the Effect: Refrigerating cooked potatoes for at least 24 hours maximizes the formation of resistant starch.

For years, potatoes have been viewed with suspicion by many carb-conscious dieters. However, a growing body of research is shedding light on how a simple preparation hack can fundamentally change their nutritional profile. It's not about making carbs disappear entirely, but rather about transforming them into a more beneficial form for your body.

The Scientific Process: Starch Retrogradation

When a potato is cooked, its starch granules absorb water and swell, a process known as gelatinization. This makes the starches highly digestible and leads to a rapid conversion into glucose, causing a spike in blood sugar. However, when the cooked potato cools, particularly in the refrigerator, a change occurs called retrogradation. The starch molecules rearrange, forming a new structure resistant to digestion. This is resistant starch.

What Exactly Is Resistant Starch?

Resistant starch isn't digested in the small intestine but travels to the large intestine. There, it acts like soluble fiber and feeds beneficial gut bacteria. The resistant starch from cooled potatoes (Type 3) reduces the calories and digestible carbs the body absorbs. The health benefits stem from this functional change.

How This Affects Carbohydrate Absorption

Converting digestible starch to resistant starch lowers the glycemic response. Cooled potatoes cause a smaller, gradual rise in blood sugar compared to hot ones. This is beneficial for managing blood sugar levels.

Benefits Beyond Lower Carbs

The conversion of potato starch offers multiple health advantages:

Improved Gut Health: Resistant starch is a prebiotic, feeding good gut bacteria. This fermentation produces short-chain fatty acids (SCFAs) like butyrate, which fuel colon cells and support gut wall integrity.
Increased Satiety: Similar to fiber, resistant starch can increase feelings of fullness, potentially aiding weight management.
Boosted Insulin Sensitivity: Regular resistant starch consumption may improve the body's response to insulin, which is crucial for metabolic health.

Maximizing Resistant Starch in Your Potatoes

To increase resistant starch, simply cook potatoes thoroughly (boiling, steaming, or baking are fine, even with skin on) and then cool them completely in the refrigerator. Refrigerating for several hours or overnight allows for maximum retrogradation. Cooled potatoes can be eaten cold or reheated; the resistant starch largely remains intact after reheating.

Comparison: Hot vs. Cooled Potatoes


Feature	Hot Potato (Freshly Cooked)	Cooled Potato (Refrigerated)
Digestibility	Starches are readily digested by enzymes.	Starches are converted into resistant starch, resisting digestion.
Blood Sugar Impact	Higher glycemic index, causing a larger and quicker blood sugar spike.	Lower glycemic index, resulting in a more controlled and gradual blood sugar rise.
Nutritional Profile	Standard nutritional content.	Higher resistant starch content, effectively acting as dietary fiber.
Caloric Impact	Higher net caloric value from digestible carbs.	Slightly lower net caloric value from carbs due to less digestion.
Gut Health	Minimal prebiotic effect.	Acts as a prebiotic, feeding beneficial gut bacteria.

Conclusion

While refrigerating cooked potatoes doesn't eliminate carbohydrates, it transforms a portion into beneficial resistant starch. This lowers the glycemic index, supports gut health, and improves insulin sensitivity. Cooking and cooling potatoes is a simple, science-backed method to enjoy them with enhanced nutritional benefits. For more information, you can refer to a study published by the National Institutes of Health (NIH).

Frequently Asked Questions

For optimal resistant starch formation through retrogradation, it is recommended to refrigerate cooked potatoes for at least a few hours, with overnight being ideal.

No, the process of creating resistant starch requires the starches to first be cooked and gelatinized before cooling. Refrigerating raw potatoes will not change their starch structure in this way.

Yes, you can reheat cooled potatoes without significant loss of the newly formed resistant starch. The retrograded starch structure is stable enough to withstand reheating.

Yes, this principle applies to many other starchy foods. Cooked and cooled rice, pasta, and oats will also develop increased levels of resistant starch.

Because resistant starch is not broken down in the small intestine, it slows down the release of glucose into the bloodstream. This prevents sharp blood sugar spikes and contributes to more stable levels.

In the large intestine, beneficial gut bacteria ferment the resistant starch, producing beneficial short-chain fatty acids (SCFAs), such as butyrate, which nourish colon cells.

The exact reduction can vary, but studies have shown that cooling can lower a potato's glycemic impact by 25–40% due to the formation of resistant starch, effectively reducing the net available carbs.