Which Has a Lower Glycemic Index, Potatoes or Sweet Potatoes?

January 10, 2026 •

3 min read

Despite the common belief that sweet potatoes are always a lower-GI choice, data shows that a baked sweet potato can have a very high glycemic index, similar to a baked white potato. The question of which has a lower glycemic index, potatoes or sweet potatoes, is far more nuanced, hinging entirely on preparation and serving temperature.

Quick Summary

The glycemic index of sweet potatoes versus regular potatoes is not a constant value and changes based on cooking method. This article compares how baking, boiling, and cooling affect the GI of both tubers and provides practical tips.

Key Points

Cooking Method is Key: Boiling a sweet potato yields a low GI, while baking it results in a high GI, similar to a baked white potato.
Cold Potatoes Have Lower GI: Cooling cooked white potatoes significantly increases resistant starch, lowering their GI into the low range.
A Matter of Preparation: A boiled sweet potato has a lower GI than a boiled white potato, but a cooled white potato can have a lower GI than a hot boiled sweet potato.
Beyond GI: Sweet potatoes offer more Vitamin A and fiber, while white potatoes contain more potassium and iron.
Additives Help: Pairing potatoes with protein, fat, or acid slows digestion and lowers the overall glycemic response of a meal.
Glycemic Load: Consider glycemic load, which factors in portion size, for a more accurate picture of blood sugar impact.

The Glycemic Index Explained

The Glycemic Index (GI) is a scale from 0 to 100 that measures how quickly a carbohydrate-containing food raises blood glucose (sugar) levels after consumption. A low GI is 55 or less, a medium GI is 56-69, and a high GI is 70 or higher. For individuals managing blood sugar, such as those with diabetes, choosing lower-GI foods can help prevent sharp spikes. However, the GI value alone doesn't provide the complete picture. The Glycemic Load (GL) is a more useful metric as it accounts for the portion size, which can dramatically affect blood sugar response.

The Surprising Impact of Cooking Method

How you prepare your potato is the single most important factor determining its GI. The high heat from baking or roasting breaks down the starches, making them more readily available for digestion and absorption, thus increasing the GI. Conversely, boiling, especially for a longer duration, can alter the starch structure and even cause some starches to leach out, resulting in a lower GI for sweet potatoes.

How Boiling Changes the Game

For sweet potatoes, boiling is the key to achieving a low GI. A sweet potato boiled for a sufficient amount of time can have a low GI of approximately 46, a stark contrast to a baked sweet potato, which can have a GI as high as 94. Boiling a regular white potato also lowers its GI compared to baking, but the result is still typically in the high GI range.

The Magic of Resistant Starch

An even more powerful technique for lowering the GI of potatoes is cooling them after cooking. This process, called retrogradation, increases the amount of resistant starch. Resistant starch acts like fiber, resisting digestion in the small intestine and slowing down glucose release. A hot, freshly boiled white potato might have a high GI, but if you refrigerate it for 12-24 hours and then eat it cold (e.g., in a potato salad), its GI can drop into the low-GI range.

Comparative Glycemic Index of Potatoes and Sweet Potatoes


Preparation Method	White Potato (approx. GI)	Sweet Potato (approx. GI)
Baked / Roasted (Hot)	88 (High)	88-94 (High)
Boiled (Hot)	73 (High)	46-63 (Low to Medium)
Boiled & Cooled	49-56 (Low)	Not typically consumed cooled
French Fries	65-85 (Medium to High)	71-76 (High)

Note: GI values can vary based on the specific potato variety and precise cooking time.

Tips for Optimizing Your Potato Intake

Prioritize Boiling for Sweet Potatoes: For the lowest GI, boil your sweet potatoes. Longer boiling times can further reduce the GI.
Go for Cold White Potatoes: If you prefer white potatoes, cook and cool them thoroughly to maximize resistant starch and lower the GI. This makes potato salad a great blood-sugar-friendly option.
Add Fat, Fiber, and Protein: Pairing either potato with healthy fats (like olive oil), protein, and fiber-rich vegetables can significantly lower the overall glycemic response of the meal.
Avoid Over-Mashing: Mashing potatoes increases their GI because it breaks down the starch into smaller particles that are easier to digest.
Control Portion Sizes: Even with low-GI foods, portion control is vital for blood sugar management.

Beyond GI: A Look at Nutritional Profiles

While GI is a key factor, both potatoes and sweet potatoes offer significant nutritional benefits.

Sweet Potatoes: Excellent source of beta-carotene (which converts to Vitamin A), supporting eye health, skin, and immunity. Higher in fiber and Vitamin C than white potatoes.
White Potatoes: Rich in potassium, important for blood pressure regulation, and a good source of Vitamin B6 and iron. Can also be a good source of resistant starch when cooked and cooled.

Conclusion: Which Tuber Comes Out on Top?

The straightforward assumption that sweet potatoes are always better for blood sugar management is incorrect. The cooking method is the decisive factor. For the lowest GI, a boiled sweet potato or a cooled white potato are the best choices. Both tubers are highly nutritious and can be part of a healthy diet, particularly for those with blood sugar concerns, by adjusting preparation methods. The overall balance of your meal, including protein, fats, and fiber, is also a crucial consideration for stabilizing glucose levels. For more information on the glycemic index, consider reviewing resources from institutions like the Harvard T.H. Chan School of Public Health.

Frequently Asked Questions

Baked sweet potatoes and baked white potatoes have similar, high glycemic index (GI) values, often around 88 or higher, as high heat breaks down their starches.

To lower the GI of potatoes, boil them instead of baking, and then cool them in the refrigerator for at least 12 hours before eating. This process increases their resistant starch content.

No, sweet potatoes are not always better. While a boiled sweet potato can have a low GI, a baked one has a high GI. The preparation method is more important than the potato type for managing blood sugar.

Boiling alters the chemical structure of the sweet potato's starches and can increase its resistant starch content, which leads to slower digestion and a more gradual rise in blood sugar.

Resistant starch is a type of carbohydrate that resists digestion. When cooked starches like potatoes are cooled, they form resistant starch, which slows down the absorption of sugar and lowers the GI.

Sweet potatoes are rich in beta-carotene (Vitamin A) and fiber, whereas white potatoes are a superior source of potassium and iron.

Yes, adding healthy fats, protein, or fiber to a meal with potatoes helps slow down the digestion and absorption of carbohydrates, leading to a smaller and slower rise in blood sugar.