During the cold winter months like these, roasted sweet potatoes come to mind. With their sweet and chewy texture, roasted sweet potatoes are a ‘representative snack’ loved by people of all ages. Nowadays, you can even buy roasted sweet potatoes at convenience stores.
However, roasted sweet potatoes can be more burdensome for those who need to manage their blood sugar than one might think. Sweet potatoes have a strong image as a health food, but their glycemic index (GI) can vary significantly depending on the cooking method and temperature.
According to the Korean Diabetes Association, both sweet potatoes and regular potatoes are classified in the grain group on the food exchange list, and they can be exchanged based on carbohydrate intake. For example, 70g of sweet potato (half of a medium-sized one) provides the same amount of carbohydrates as 140g of potato. In other words, sweet potatoes are more concentrated in carbohydrates than potatoes, which means they can have a significant impact on blood sugar even in smaller amounts.
Blood Sugar Response Can Vary Up to Twice Depending on Cooking Method, Temperature, and Amount Consumed
However, the glycemic index (GI) of sweet potatoes can change dramatically based on the cooking method. The GI of roasted sweet potatoes ranges from 79 to 94, while boiled sweet potatoes range from 41 to 50. On average, roasted sweet potatoes have a GI that is 90% (58-129%) higher than that of boiled sweet potatoes. During the roasting process, moisture is lost, and the starch is completely gelatinized, leading to faster digestion. Even the same sweet potato becomes sweeter and the carbohydrates are absorbed more quickly when roasted.
Conversely, boiled sweet potatoes have the lowest GI among cooking methods. This is because the starch is less broken down during the cooking process in water, and moisture is absorbed, diluting the sugar concentration. Steamed sweet potatoes and those cooked in a microwave fall in between. In other words, research has confirmed that the blood sugar impact is greatest with roasted sweet potatoes, followed by microwave-cooked and steamed sweet potatoes, with boiled sweet potatoes having the lowest impact.
Additionally, cooled sweet potatoes raise blood sugar less than hot ones. When sweet potatoes are cooled, some of the starch converts to ‘resistant starch,’ slowing digestion and moderating the rate of blood sugar increase. The same principle applies to potatoes. A cooled potato salad is less burdensome on blood sugar than a hot potato.
Potatoes Follow the Same Principle as Sweet Potatoes…Baked and Mashed Potatoes Raise Blood Sugar Quickly
Like sweet potatoes, the blood sugar response of potatoes can vary greatly depending on the cooking method. Baked or mashed potatoes completely break down the starch, raising blood sugar quickly, while boiled potatoes show a relatively lower blood sugar response. Considering that both foods belong to the grain group, comparing them when choosing winter snacks is beneficial for blood sugar management.
If You're Worried About Blood Sugar…Here’s How to Eat Sweet Potatoes and Potatoes
First, if possible, choosing boiled sweet potatoes and potatoes is the safest option.
Second, if you want to eat roasted sweet potatoes or baked potatoes, it’s better to reduce the amount and eat them with protein and dietary fiber.
Third, eating them cooled rather than hot helps lower the blood sugar response.
Fourth, when consuming sweet potatoes and potatoes together, it’s important to remember that according to the food exchange list provided by the Korean Diabetes Association, you should eat less sweet potato and more potato to match the same amount of carbohydrates.
Sweet potatoes and potatoes are undoubtedly healthy foods. However, the blood sugar response can vary greatly depending on the cooking method and consumption style. Enjoy the sweetness of roasted sweet potatoes in winter, but if you’re concerned about blood sugar, try adjusting the cooking method, temperature, and order of consumption just a little.
[Frequently Asked Questions]
Q1. Why do roasted sweet potatoes raise blood sugar more quickly?
A1. Because moisture is lost during the roasting process and the starch is completely broken down, digestion becomes very fast. Even the same sweet potato has a significantly higher glycemic index (GI) when roasted, leading to a quicker rise in blood sugar.
Q2. How should I adjust the amounts of sweet potatoes and potatoes when eating?
A2. According to the Korean Diabetes Association's food exchange list, 70g of sweet potato provides the same amount of carbohydrates as 140g of potato. Carbohydrates are more concentrated in sweet potatoes than in potatoes. Therefore, sweet potatoes can have a greater impact on blood sugar even in smaller amounts.
Q3. Why is cooled sweet potato better for blood sugar than hot sweet potato?
A3. When sweet potatoes are cooled, some of the starch converts to ‘resistant starch,’ slowing digestion and moderating the rate of blood sugar increase. The same principle applies to potatoes.
