Three things you probably didn't know about potatoes:
- They're packed with nutrients!
- The American Diabetes Association includes potatoes on its list of myths about diabetes.
- Despite their high amount of carbs, potatoes can be low glycemic with special preparation.
Check out the free printable low glycemic meal plan when you're done here.
Mostly composed of carbohydrates, potatoes are high carb and they will raise blood sugar, but the glycemic index (GI) of a potato ranges from low to high.
The 2021 glycemic index tables report over 50 varieties of potatoes from across the world, with various cooking and preparation methods.
Overall, potatoes are high glycemic, except when cooked and cooled. Potatoes cooled and served cold are low glycemic. You can call it a hack, but it's just plain science!
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Potato Glycemic Index & Glycemic Load
Potatoes range from low glycemic at 38 to high glycemic at 103. The average is 73, which falls in the high glycemic range.
- The potato holding the 38 GI value is identified as a "novel clone" grown in Alberta, Canada and harvested prior to maturity. It was cubed and boiled for 15 minutes.
- The Maiflower potato from Australia holds the 103 GI. It was sliced and boiled for 9 minutes.
Unfortunately, the international tables have data compiled from multiple tests that span decades, so there's no planned consistency in the data. That makes it difficult to group the results, but here's what can be summarized:
- All cooking methods were high glycemic: boiled, baked, dehydrated, mashed, roasted, and microwaved.
- Peeled or unpeeled did not significantly affect glycemic index.
- French fries were moderate or medium GI at 65.
- Together, the type of potato and how it's cooked determine the glycemic index value, but the data is too inconsistent to recommend the best pairing of potato and cooking method.
- Eating potatoes cold has a significantly lower glycemic effect.
Serving potatoes cold significantly lowered their GI. Potatoes cooked, then cooled for at least 24 hours, had an average low glycemic index of 49.
But what happens if they're reheated?
The data is unclear on potato GI after reheating. Only a handful of studies on the international tables tested reheated potatoes. They show reheated potatoes to be high glycemic, but they don't specify time or methods of cooling or reheating. What is clear is that potatoes cooled for a minimum of 24 hours and served cold fell to the low glycemic range.
Glycemic Load
Glycemic load (GL) is based on how many carbs are in one serving.
As a single carbohydrate choice, which is a portion equivalent to 15 carbs, or half of a small russet potato, the GL for potatoes served hot is 12 (medium).
For the same serving size served cold, the GL is 7 (low).
Why do cold potatoes have a lower GI?
Potatoes naturally contain resistant starches. Resistant starches act like fiber, resisting digestion and fermenting in the colon instead.
Cooling potatoes increases their resistant starch, thereby lowering the glycemic index.
Reheating Potatoes
When reheated, some of those resistant starches revert to starch, increasing the glycemic index. This starch conversion is a natural process that takes place in several foods, but we don't know how much resistant starch reverts to starch when potatoes are reheated. The SPUD Project, once complete, will hopefully answer that question.
GI of Potatoes in North America
This data was taken from a 2005 study entitled "Glycemic Index of Potatoes Commonly Consumed in North America." These values are included in the international tables.
| Type of Potato | Glycemic Index | Glycemic Range |
|---|---|---|
| Russet | 77 | High |
| Instant mashed | 88 | High |
| California white | 72 | High |
| Prince Edward Island white | 73 | High |
| Red (served hot after cooking) | 89 | High |
| Red (cooled 12-24 hrs, served cold) | 56 | Medium |
| French fries | 64 | Medium |
Can diabetics eat potatoes?
Yes, a diabetic can eat potatoes. The American Diabetes Association includes potatoes on their list of myths, noting that they don't need to be avoided but portioned.
Of course, if your blood sugar is high after eating potatoes, you'll need to be more strategic with how to incorporate them, or even omit them from your diet.
Potato Nutrition
This information was pulled from the USDA FoodData Central database. It applies only to a small russet potato, approximately 2½ inches in diameter (138g), baked with the skin on.
- Calories - 131
- Fat - 0g
- Carbs - 30g
- Fiber - 3g
- Protein - 4g
Potatoes are rich in potassium and vitamins C and B6, and they have a decent amount of magnesium.
FAQs
No; the vast majority of potatoes are high glycemic with the exception of potatoes that are boiled, cooled for at least 24 hours, and served cold: such potatoes are low glycemic, averaging a GI of 49.
Yes, potatoes are mostly composed of carbohydrates so they will raise blood sugar levels.
Marfona and Carisma potatoes boiled 15 mins and 12 mins, respectively, have the lowest glycemic load as reported on the international GI tables.
Yes; cold potatoes are good for diabetics because they have more resistant starch than warm potatoes, making them low glycemic.
The 2021 international glycemic index tables show the average GI of a cold, boiled potato is 49.
Boiling lowers a sweet potato's glycemic index, not other potatoes.
Summary
Potatoes can be low glycemic or high glycemic depending on the type of potato and the cooking method. Cold potatoes, like in potato salad, have the lowest glycemic index, whereas the average potato served hot is high glycemic. We don't know the perfect combination of type of potato and cooking method, but hopefully the SPUD project will answer that question once it has concluded. As of now, cold potatoes are the lowest glycemic, but whether hot or cold, portioning is the key to incorporating them into your diet and balancing blood sugar.
Recipes with Potatoes
More Glycemic Index Info
- Can diabetics eat carrots?
- Fruit for diabetics
- Sweet potato glycemic index
- Is watermelon good for diabetes?
- Glycemic index of mango
More to See
Share with us how you eat potatoes in the comments below.
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