Does boiling potatoes reduce GI?

November 17, 2025 •

3 min read

While many believe that boiled potatoes have a high glycemic index, studies show that how you treat them after boiling can dramatically change their effect on blood sugar. The key to reducing the GI is a simple trick involving temperature control, leveraging a natural process that increases the potato's health benefits. This method can make a significant difference for anyone managing their blood glucose levels.

Quick Summary

Boiling and then cooling potatoes significantly increases resistant starch, lowering their glycemic index. Potato variety and serving temperature are key factors impacting blood sugar response.

Key Points

Boiling and cooling reduce GI: Cooling boiled potatoes creates resistant starch, significantly lowering their glycemic index.
Temperature matters: Potatoes eaten cold or reheated after chilling have a much lower GI than those consumed fresh and hot.
Variety is important: Waxy potato varieties like red or fingerling have a naturally lower GI than starchy varieties like Russet.
Resistant starch benefits gut health: The resistant starch formed through the cook-cool method acts as a prebiotic, supporting beneficial gut bacteria.
Boiling is better than baking: Boiling generally results in a lower GI compared to high-heat methods like baking, especially for starchy potatoes.
Adding fiber, fat, and protein helps: Combining potatoes with other foods like salads, oils, or proteins can further slow digestion and lower the overall glycemic load of a meal.
Leaving the skin on adds fiber: Keeping the potato skin on while boiling adds extra fiber, which also helps moderate blood sugar levels.

The Science Behind Potatoes and Glycemic Index

To understand whether boiling potatoes can reduce their glycemic index (GI), it's important to first grasp what GI represents. The glycemic index is a value assigned to foods based on how quickly and how much they raise blood glucose levels after consumption. Foods are classified as low, medium, or high GI, with high GI foods causing a more rapid spike in blood sugar.

How Starch Changes with Heat

Potatoes are primarily composed of starch. Cooking causes starch granules to gelatinize, making them easier to digest and thus increasing GI. This is why most freshly cooked potatoes typically have a high GI.

The Role of Resistant Starch in Lowering GI

The key to lowering potato GI after boiling is cooling, which induces retrogradation.

The Magic of Cooking and Cooling

Cooling boiled potatoes, especially for 12-24 hours, causes starch molecules to re-form into resistant starch (RS). Resistant starch is not digested in the small intestine but ferments in the large intestine, acting as a prebiotic. This process can lower potato GI by 25-40%. Even light reheating doesn't fully reverse resistant starch formation.

Boiling vs. Other Cooking Methods

Cooking methods impact potato GI. While hot boiled potatoes have a moderately high GI, they're often lower than other preparations.

Boiling: Followed by cooling, boiling is best for increasing resistant starch and lowering GI.
Baking: Baking at high temperatures significantly increases GI, with baked Russet potatoes potentially exceeding a GI of 100.
Mashing: Mashing breaks down cell walls, increasing starch digestibility and GI.
Frying: Frying adds fat, which slows digestion and contributes to a moderate GI, but also adds unhealthy components.

Choosing the Right Potato Variety

The type of potato affects its GI.

Waxy Potatoes: Varieties like red or fingerling are lower in starch and moisture, resulting in a lower GI, especially when boiled.
Starchy Potatoes: Russet or Idaho potatoes are higher in starch and have a higher GI.

Comparison Table: GI of Potatoes by Preparation


Preparation Method	Potato Variety	Serving Temp	GI Value	Notes
Boiled	Red Potato	Hot	~89	High GI due to gelatinized starch
Boiled, Cooled	Red Potato	Cold	~56	Significant reduction from resistant starch
Boiled, Cooled, Reheated	Various	Warm	Lower than hot	Retains resistant starch benefits
Baked	Russet	Hot	~111	Very high GI due to intensive heat
Mashed	Various	Hot	~78-82	Starch is highly broken down
Instant Mashed	Various	Hot	~88	Highly processed, high GI

How to Maximize the GI-Lowering Effect

To minimize the glycemic impact of boiled potatoes:

Choose a waxy variety: Opt for lower-starch types like red potatoes.
Boil with the skin on: The skin's fiber helps slow digestion.
Do not overcook: Cook only until tender.
Cool completely: Refrigerate for 12-24 hours to maximize resistant starch.
Serve cold or reheat lightly: Resistant starch remains mostly intact.
Combine with other foods: Eating potatoes with protein, fats, or acids can lower the overall meal's glycemic load. For more on resistant starch, see Resistant Starch: Promise for Improving Human Health.

Conclusion: Making Smarter Choices

Does boiling potatoes reduce their GI? Not significantly on its own, especially when hot. However, boiling followed by cooling is effective in lowering GI by creating resistant starch. By selecting waxy varieties and pairing with other healthy foods, you can include potatoes in a blood-sugar-conscious diet. It's about preparation, not avoidance.

The Bottom Line: Can You Enjoy Boiled Potatoes?

Yes, by boiling and then cooling potatoes, you maximize resistant starch, making them a more blood-sugar-friendly option than other preparations. This allows you to benefit from potatoes' nutrients like potassium and Vitamin C with less glycemic impact.

Frequently Asked Questions

No, a freshly boiled potato is not considered low GI. The act of boiling gelatinizes the starch, making it easily digestible and causing a relatively rapid rise in blood sugar.

For maximum effect, it is recommended to cool boiled potatoes in the refrigerator for at least 12-24 hours. This time allows for a process called retrogradation, which significantly increases resistant starch.

No, the GI-lowering effect from cooling is not entirely reversed by reheating. The resistant starch formed during the cooling process is largely retained, meaning reheated boiled and cooled potatoes still have a lower GI than freshly cooked ones.

Yes, cold, boiled potatoes can be a good option for people with diabetes due to their higher resistant starch content and lower GI. Portion control and pairing with other healthy foods are still important for managing blood sugar effectively.

Waxy potato varieties, such as red or fingerling potatoes, are the best choice for a low GI diet. They contain more amylose starch, which is more prone to forming resistant starch when cooled.

While mashing typically increases GI, you can still improve it. Start by boiling and cooling your potatoes for at least 12 hours. Then, mash them and add healthy fats like olive oil or butter to further slow digestion.

Yes, adding acidic ingredients like vinegar or lemon juice to potato dishes can help slow the digestion of carbohydrates and reduce the overall glycemic impact of the meal.