Why Sweet Potatoes Have a Lower Glycemic Index Than White Potatoes

If you’ve ever been told to avoid potatoes for blood sugar reasons, you’re not alone. But here’s the surprising truth: not all potatoes affect blood sugar the same way—and it’s not just about fiber. This is something that confused me (and a lot of people!) because if you look at the nutrition label, the differences between white potatoes and sweet potatoes are minimal!

While sweet potatoes have only about 1 gram more fiber per cup than white potatoes, they have a much lower glycemic index (GI) and glycemic load (GL). A boiled white potato has a GI of around 82, while a boiled sweet potato comes in closer to 44. That’s a big difference!

So why the gap?

• Starch type matters. White potatoes are high in amylopectin, a fast-digesting starch, while sweet potatoes contain more amylose, which digests more slowly.

• Sweet potatoes contain natural sugars like fructose and sucrose, which raise blood sugar more slowly than the pure glucose starches found in white potatoes.

• Antioxidants and polyphenols in sweet potatoes (especially beta-carotene) can slow digestion and blunt blood sugar spikes.

• Texture after cooking plays a role too. Boiled sweet potatoes tend to be denser, while white potatoes fluff up, making them easier—and quicker—to digest.

So no, you don’t have to avoid potatoes. But sweet potatoes may be a better option for blood sugar stability—especially when boiled and paired with other fiber or protein-rich foods.