All potato varieties are naturally sugar-free in the traditional sense — they contain no added sugars and have extremely low natural sugar content.
According to USDA FoodData Central data, a medium raw potato (150g) contains only about 1-2 grams of natural sugars (primarily glucose, fructose, and sucrose), which represents less than 1% of the potato's total weight. The vast majority of a potato's carbohydrate content (around 35-37 grams in a medium potato) comes from starch, not sugar.
However, it's important to understand that potatoes do convert to glucose during digestion. The glycemic index data shows significant variation by variety and preparation method: waxy/new potato varieties have lower glycemic indexes (GI 56-69 when boiled) compared to floury varieties like Russet (GI 78-101 boiled, GI 111 baked), according to research published in Diabetes Care and the American Journal of Clinical Nutrition.
For the lowest glucose impact, choose waxy potato varieties (like new potatoes, fingerlings, or red potatoes) and prepare them by boiling rather than baking. Cooling cooked potatoes increases resistant starch formation, which further reduces the glycemic response as noted in European Journal of Clinical Nutrition studies.