Does Refrigerating Raw Potatoes Lower the Glycemic Index? Unpacking the Science

October 18, 2025 •

4 min read

A study on cooking methods and glycemic index found that cooling cooked potatoes can lower their GI by as much as 40%. However, the common misconception that does refrigerating raw potatoes lower the glycemic index? is not only false but can also be unsafe.

Quick Summary

Cooling cooked potatoes triggers retrogradation, converting starch into resistant starch and lowering the glycemic index. Refrigerating raw potatoes does not produce this effect and can increase the formation of reducing sugars that lead to harmful compounds when fried.

Key Points

Misconception Debunked: Refrigerating raw potatoes does not lower their glycemic index; it's the cooling of cooked potatoes that is effective.
Resistant Starch Creation: Cooking potatoes followed by cooling them triggers retrogradation, a process that converts some starches into resistant starch.
Blood Sugar Control: This resistant starch is not fully digested, which slows glucose absorption and leads to a lower blood sugar spike compared to freshly cooked potatoes.
Safety Concerns: Refrigerating raw potatoes can lead to the formation of reducing sugars, which can produce harmful acrylamides when subsequently cooked at high heat.
Health Benefits: The resistant starch formed after cooling supports gut health and can increase feelings of fullness.
Reheating Retains Benefit: Reheating cooled potatoes does not eliminate all the resistant starch, allowing you to still benefit from a lower glycemic impact.

The Basics of Glycemic Index and Potatoes

The glycemic index (GI) is a ranking system for carbohydrate-containing foods based on how quickly and how much they raise blood sugar levels after eating. Foods with a high GI are rapidly digested and absorbed, causing a quick spike in blood glucose, while low-GI foods produce a slower, more gradual rise. Potatoes are a nutrient-rich staple food, packed with fiber, vitamins, and minerals. However, depending on the variety and preparation, potatoes can have a moderate to high GI. The primary factor influencing a potato's GI is its starch content and structure, which can be modified by how it is cooked and served.

Starch Gelatinization During Cooking

When a potato is cooked, its starch granules absorb water and swell, a process known as gelatinization. This process makes the starch more accessible and easier for digestive enzymes to break down into glucose. This is why eating freshly boiled or mashed potatoes typically leads to a higher blood sugar spike compared to their cooled counterparts.

The Real Way to Lower Glycemic Index: Cooking and Cooling

Contrary to the myth about refrigerating raw potatoes, the key to lowering a potato's glycemic impact lies in a process called retrogradation, which occurs after cooking and cooling.

The Science of Retrogradation

After boiling or baking, if the potato is allowed to cool completely, some of the gelatinized starch molecules reorganize and crystallize into a form that resists digestion. This type of starch is known as resistant starch (specifically, type 3). This newly formed resistant starch passes through the small intestine largely undigested, acting more like soluble fiber.

Benefits of Resistant Starch

Lower Blood Sugar Spike: Because resistant starch is not easily broken down into glucose, it reduces the overall impact on blood sugar levels. Studies have shown that consuming cooled or reheated potatoes can significantly reduce their glycemic impact compared to when they are eaten hot.
Improved Gut Health: In the large intestine, resistant starch is fermented by beneficial gut bacteria, producing short-chain fatty acids that support a healthy gut microbiome.
Increased Satiety: Like fiber, resistant starch can contribute to a feeling of fullness, which can aid in weight management.

The Harmful Side of Refrigerating Raw Potatoes

Refrigerating raw potatoes is not the method for generating resistant starch and is actually discouraged by food safety guidelines.

Risk of Acrylamide Formation

Storing raw potatoes at very low temperatures (in the refrigerator) can lead to 'cold-induced sweetening'. In this process, the starches convert into reducing sugars, which can react with amino acids when cooked at high temperatures, like frying or roasting. This reaction produces acrylamide, a chemical linked to cancer risk. For this reason, raw potatoes are best stored in a cool, dark, and well-ventilated space, not the refrigerator.

Raw Refrigerated vs. Cooked and Cooled Potatoes: A Comparison


Feature	Raw Potatoes (Refrigerated)	Cooked & Cooled Potatoes	Effect on Glycemic Index
Preparation	No cooking required; simply chilled raw.	Cooked via boiling or baking, then refrigerated for several hours or overnight.	N/A
Starch Content	Starch converted to simple sugars due to cold exposure.	Starches undergo retrogradation, increasing resistant starch.	Lowers the GI of the final meal compared to hot potatoes.
Safety	High-temperature cooking after refrigeration can produce acrylamide, a potential carcinogen.	Safe when prepared and cooled correctly.	N/A
Health Benefits	No health benefits; potentially unsafe.	Increased resistant starch content, which benefits blood sugar control and gut health.	N/A

How to Properly Prepare Potatoes to Lower Their Glycemic Index

If you want to reap the benefits of resistant starch and lower the GI of your potatoes, follow this simple process:

Cook the Potatoes: Boil, bake, or microwave your potatoes until they are tender. Boiling and baking are effective methods for gelatinizing the starch.
Cool Them Down: Once cooked, allow the potatoes to cool completely. For maximum resistant starch formation, refrigerate them for at least 12 hours. This is the retrogradation phase.
Serve Cold or Reheat: You can enjoy the potatoes cold, as in a potato salad, or reheat them. Reheating will not eliminate all the resistant starch, so you still retain a significant portion of the GI-lowering effect.

Conclusion

To be clear, refrigerating raw potatoes does not lower their glycemic index. This widespread myth is based on a misunderstanding of how resistant starch is formed. The correct method for creating beneficial resistant starch is to first cook the potatoes and then cool them. This cooking-and-cooling process triggers retrogradation, which creates a type of starch that resists digestion, leading to a smaller, slower blood sugar increase. By adopting this simple preparation method, you can enjoy potatoes as part of a balanced, blood-sugar-conscious diet. Healthline: What's the Best Way to Store Potatoes?

Frequently Asked Questions

No, you should not refrigerate raw potatoes. The cold temperature converts starch into reducing sugars, which can produce a harmful chemical called acrylamide when the potatoes are cooked at high heat.

The process is called retrogradation. It occurs when cooked, starchy foods like potatoes are cooled, causing some of the digestible starches to reorganize into indigestible resistant starch.

While some resistant starch forms as soon as a potato cools, for maximum effect, it is recommended to chill cooked potatoes in the refrigerator for at least 12 hours, or ideally overnight.

No, reheating does not reverse all the benefits. While some changes may occur, cooled and reheated potatoes still have a lower glycemic impact than potatoes served hot immediately after cooking.

Yes. The resistant starch produced by cooling cooked potatoes acts as a fiber that can improve blood sugar control, benefit gut health by feeding good bacteria, and increase satiety.

Raw potatoes should be stored in a cool, dark, and well-ventilated area, such as a pantry or basement. This prevents the formation of reducing sugars and sprouts.

Any starchy potato can benefit from the cooling and retrogradation process. Some varieties naturally have a lower GI, like new or sweet potatoes, but the cooling technique can be applied to most varieties to achieve a beneficial effect.