What Potatoes Have the Highest Glycemic Index?


Q: I keep reading that potatoes are high glycemic index and are therefore to be avoided. If you are eating, say, boiled potatoes with a meal that includes meat, doesn’t that retard the quick digestion of the potato and make it a valid part of a healthy meal?

A:Potatoes can have a high glycemic index (GI) – a measurement of how quickly a food raises blood sugar—and are linked to weight gain. But Katelyn Castro, a dietetic intern at Tufts’ Frances Stern Nutrition Center, says, “The type of potatoes and preparation methods have a big impact on its glycemic response. Recent studies have found that waxy potatoes, like fingerling and red potatoes, have a lower glycemic index than starchy potatoes, like Russet and Idaho potatoes. The cooking method also alters the glycemic index of a potato. Boiled and roasted potatoes have the lowest GI (both 59), while baked potatoes are higher (69) and mashed and instant potatoes have the highest GI (78 and 82, respectively).

“Looking at the other foods eaten with the potato is also important, as you were thinking. One study found that when protein and fat are added to foods high in carbohydrates, this can lower the glycemic index of the food. Normally, foods high in carbohydrates, like potatoes, are quickly digested, broken down into glucose and released into the blood. When you add foods high in protein and fat, like meat or butter (GI = 0), this can slow digestion and slow the release of glucose into the blood. The study suggested that the protein and fat may trigger gut hormones and increase insulin secretion in order for this reduced glucose response to occur.

“While potatoes may have gotten a reputation of having a high glycemic index, by choosing specific types of potatoes, cooking methods and other additions to your meal, you can still enjoy potatoes in moderation without seeing spikes in your blood glucose levels.”


  1. I am curious to know the study’s definitions of roasted and baked potatoes. Are the preparation methods described? Thank you.

  2. How would a boiled potato have a lower index than mashed since you have to boiled the potato before mashing it? I do get that instant mashed would be different

    • The simple act of mashing the potato (you are making the potato bits smaller and finer) makes it more quickly digestible thus the glycemic index is higher.

      • By the time the unmashed patato gets in your stomach it’s going to be just as if not more mashed up than if you use a potato masher, so I really don’t see that argument holding up too well.

        However, cooled potatoes mashed or not should contain more indigestible starches which should reduce glucose absorption rate.

        • Not true at all. Mashed potatoes are significantly more broken down when they go in your mouth (where digestion starts) and they require little mechanical breakdown from your teeth before they can be swallowed. They are uniform in consistency, almost like a thick paste.

          Chewing up whole potatoes still leaves them in small “chunks” that are appreciably larger than mashed consistency. Someone gave you the explanation, and it was correct. Think of oats: Quick oats have a higher GI than whole rolled oats. Why? Because the former are significantly more broken down and require less effort to digest, ergo that impact blood sugars more/faster.


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