Are Sweet Potatoes or Yams Better for Blood Sugar?

Sweet potatoes and yams are two completely different vegetables that can affect blood sugar in different ways.
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Sweet potatoes versus yams: You probably didn't know there was a difference, right?

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Turns out, there is. Besides deriving from completely different tuberous root vegetable families, per the Carnegie Museum of Natural History, sweet potatoes and yams also taste different.

While yams are starchier and less sweet, sweet potatoes have that recognizable sweetness. Both come in several varieties, like purple yams and garnet sweet potatoes.

No matter the variety you choose, recipes with sweet potatoes and yams are plenty. But, if you have diabetes (or are watching your blood sugar), you may be wondering if you can enjoy either.

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Fear not: You can, but you'll want to pay attention to cooking method and portion size. Learn how to incorporate both into a diabetes-friendly or low-glycemic index diet here.

How to Find Diabetes-Friendly Foods

When determining how a certain food will affect your blood sugar, consider its glycemic index (GI). This is a method used to figure out how a food will raise your blood glucose or sugar, per Harvard Health Publishing.

Scores range from zero to 100. The lower the glycemic index, the better. Higher scores will have a larger and more rapid effect on blood sugar.

Foods with a low GI, from zero to 55, have slowly digested starches. Moderate GI scores are 56 to 69, while a high GI rating (between 70 and 100) indicates food with quickly digested starches (i.e., foods that cause blood sugar spikes and crashes).

Are Sweet Potatoes Good for People With Diabetes?

Sweet potatoes are a good choice of "starchy" carbohydrates that people with diabetes can enjoy, per the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Here's why:

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Sweet Potato Nutrition

According to the USDA, 1 cup of sweet potato has:

  • 114 calories
  • 2.1 g protein
  • 0.1 g fat
  • 27 g carbohydrates
  • 4 g fiber
  • 6 g sugar

Carbohydrates in Sweet Potatoes

One cup of sweet potato has 27 grams of carbohydrates, per the USDA.

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While carbohydrate-dense foods can quickly increase your blood sugar levels, sweet potatoes also have protein and fiber — both of which may help combat blood sugar spikes experienced after eating carbohydrate-dense foods, according to a small January 2016 study in Diabetes, Obesity & Metabolism.

Glycemic Index of Sweet Potatoes

The GI for sweet potatoes ranges between 44 and 94, depending on preparation, per the University of Sydney's GI Search.

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Depending on cooking method (such as steaming, baking or dehydrating), sweet potato flesh and skin may be considered low and medium GI foods, which may be beneficial for people with diabetes or insulin resistance, according to a 2012 study in the Journal of Nutrition and Metabolism.

Potassium, Vitamin A and C

Sweet potatoes are also rich in potassium and vitamins A (in the form of beta-carotene) and C, making them an all-around solid food choice whether you have diabetes or not, per the USDA.

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Tip

Aim to choose nutrient-dense carbohydrates packed with fiber, vitamins and minerals, while also limiting added sugars, sodium and saturated fats on a diabetes-friendly diet. That means sweet potatoes are one of the "starchy" carbs you can safely eat, per the American Diabetes Association (ADA).

Types of Sweet Potatoes

There are hundreds of sweet potato varieties grown all over the world. Here are a few of the most popular, all of which contain fiber and helpful antioxidants:

  • Beauregard: Most common in grocery stores and good for all-purpose baking and cooking
  • Murasaki: Also known as "Japanese" or "white" sweet potatoes
  • Okinawa: Bright purple sweet potatoes

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Are Yams Good for People With Diabetes?

Yams have a lower GI than sweet potatoes, and can be part of a diabetes-friendly diet. Here's why:

Yam Nutrition

According to the USDA, 1 cup of yams has:

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  • 177 calories
  • 2.3 g protein
  • 0.3 g fat
  • 42 g carbohydrates
  • 6 g fiber
  • 0.8 g sugar

Carbohydrates in Yams

One cup of yams has 42 grams of carbohydrates, according to the USDA. Six of those grams come from fiber and 0.8 grams come from sugar.

While sweet potatoes have slightly more protein and fat, yams have a significant amount of fiber, making them a complex carbohydrate (i.e., a good choice for those with diabetes), per the ADA.

In fact, eating yams (and extracts from the vegetable) is linked with better blood sugar control in people with type 2 diabetes, according to a September 2021 study in the British Journal of Nutrition.

Glycemic Index of Yams

Yams range from 35 to 77 on the GI, depending on preparation, per the University of Sydney's GI Search. The lower rating applies to a 1-cup serving of boiled yams, while the higher rating applies to yams peeled and roasted on preheated charcoal.

A February 2021 study in ‌ Food Science and Nutrition‌ found boiled yams produce a lower glycemic index, and can be included in the preparation of lower GI diets for people with diabetes.

Potassium, Manganese and Vitamin B

Both sweet potatoes and yams are a good source of potassium, per the USDA. Yams also have manganese, which helps the body form connective tissue and bones, regulate blood clotting factors and regulate sex hormones, according to Mount Sinai. They also have vitamin B6, which supports nervous system and immune health, per the Mayo Clinic.

Types of Yams

Yams of international varieties are harder to find in the United States. Here are five popular types enjoyed around the world:

  • Red yams: Most often sold as "garnet sweet potatoes" in the United States
  • Tropical yams: Produced in Latin America, India and Africa, this variety tastes like regular potatoes
  • Filipino purple yam (ube): A sweet, lavender-colored yam used in desserts
  • White and yellow guinea yams: Produced in West Africa, this variety can be used as a substitute for regular mashed potatoes

Do Yams and Sweet Potatoes Spike Blood Sugar?

Despite the name, both sweet potatoes and yams have amounts of sugar that are tolerable for people with diabetes. One cup of sweet potato has 6 grams of sugar, and 1 cup of yams has 0.5 grams of sugar, per the USDA.

Because both have significant sources of fiber, protein and fat compared to carbohydrate value, they are safe and nutritious choices, in moderation, for people with diabetes, per the ADA.

Tip

How you prepare both of these starchy vegetables makes a difference when it comes to watching your blood sugar. If you are frying sweet potatoes or putting either into a casserole with added sugars, syrup and marshmallows, for example, they may have too much sugar for people with diabetes.

What Are Good Portion Sizes of Sweet Potatoes and Yams?

Before you fill your plate with sweet potato and yam side dishes, note that serving size is also important when keeping blood sugar and diabetes in mind.

"Too much of any type of carbohydrate can lead to unwanted blood sugar spikes," says Blake Metcalf, RD, CDE, registered dietitian and assistant professor at Arkansas Colleges of Health Education.

Carbohydrates, like sweet potatoes and yams, should take up about a quarter of your plate, according to the Plate Method recognized by the ADA. (The Plate Method divides your plate into three sections: half non-starchy vegetables, a quarter protein and a quarter carbohydrates.)

Tip

Portion size can also depend on body size, appetite and activity levels; there is no magic number of carbohydrates for everyone. The ADA recommends talking to a dietitian or certified diabetes educator to determine the right portion for you.

How to Cook Diabetes-Friendly Sweet Potatoes and Yams

If you have diabetes and are craving these comforting, hearty vegetables, you'll also need to consider how to best prepare them. Some holiday dishes can have added sugar, like traditional candied yams or sweet potato casserole topped with marshmallows.

Added sugars increase the total carbohydrate count of a dish, and can affect how much or how quickly your blood sugar rises, according to the ADA.

For a diabetes-friendly take on sweet, cinnamon-y fall recipes, try a plain sweet potato or yam with a sprinkle of cinnamon.

Other ways to enjoy them include, per the Produce for Better Health Foundation:

  • Baked, roasted or steamed whole
  • Mashed
  • Diced and tossed into homemade salads
  • Sliced and baked into homemade fries. (Quarter and drizzle with olive oil, then bake at 400 degrees for 40 to 60 minutes.)
  • Served in place of tomato slices in sandwiches

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Are Sweet Potatoes or Yams Better for Blood Sugar?

Both can be good for people with diabetes when eaten in moderation and without added sugars.

People with diabetes should aim to eat between 45 and 60 grams of carbohydrates per meal, per the ADA. That means either a sweet potato or yam would fit into a diabetes-friendly diet.

If you are keeping a careful eye on your blood sugar, though, boiled yams may be the best option, as they have the lowest glycemic index.

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