Most types of potatoes, such as the common russet, have a high glycemic index. This means they increase blood glucose more than most other foods containing the same amount of carbohydrate. However, this varies by potato type and processing method. For example, frying potatoes, or cooling them after cooking, tends to lower their glycemic index.[1] Potatoes also have a high insulin index, meaning they increase insulin secretion more than most other foods.[2] The health implications of this aren’t entirely clear. Observational studies report no consistent association between the habitual glycemic index of the diet and body mass index, a measure of body fatness. Similarly, randomized controlled trials report no consistent effect of glycemic index on body weight.[3] In contrast, observational studies report that diets higher in glycemic index tend to be associated with a higher risk of developing type 2 diabetes,[4][5] and a higher risk of cardiovascular disease in women but not men.[6][7][8] In addition, people with diabetes may have a harder time controlling their blood sugar levels when they eat high-glycemic foods.[9]
When considering potatoes specifically, there is no consistent association between the intake of boiled, baked, or mashed potatoes and cardiovascular risk in observational studies, but they are correlated with a slightly higher risk of type 2 diabetes. Intake of fried potatoes is more strongly associated with the risk of cardiovascular disease and type 2 diabetes in these studies, despite the lower glycemic index of fried potatoes.[10][11]
Potatoes contain oxalates, which can contribute to the formation of kidney stones in susceptible people.[12][13]
Potatoes also contain the toxic glycoalkaloids solanine and chaconine, which can cause digestive distress and in very rare cases can be fatal. These are only present in potentially dangerous amounts in potatoes that are green, damaged, diseased, and potato sprouts. Peeling potatoes removes most of their glycoalkaloid content.[14]
Per calorie, potatoes are not as dense in vitamins and minerals as low-calorie vegetables like greens, broccoli, and carrots. This isn’t necessarily a problem if potatoes are eaten as a starch alongside vegetables, as one would eat rice or bread. But if they’re viewed as a vegetable and eaten instead of low-calorie vegetables, they may lead to a lower intake of vitamins and minerals and a higher calorie intake.