Yams are also a tuber vegetable.

Their scientific name is Dioscorea, and they originate in Africa and Asia. They are now commonly found in the Caribbean and Latin America as well. Over 600 varieties of yams are known, and 95% of these are still grown in Africa.

Compared to sweet potatoes, yams can grow very large. Size can vary from that of a small potato to up to 5 feet (1.5 meters). Not to mention, they can weigh up to an impressive 132 pounds (60 kgs) (2Trusted Source).

Yams have some distinct characteristics that help distinguish them from sweet potatoes, mainly their size and skin.

They are cylindrical in shape with brown, rough, bark-like skin that is difficult to peel, but it softens after heating. The flesh color varies from white or yellow to purple or pink in mature yams.

Yams have a unique taste, too. Compared to sweet potatoes, yams are less sweet and much more starchy and dry.

They also tend to have a good shelf life. However, certain varieties store better than others.

In the US, true yams can be tough to find. They are imported and rarely found in local grocery stores. Your best chances of finding them are in international or ethnic food stores.

Summary:
True yams are an edible tuber originating in Africa and Asia. There are over
600 varieties, which vary widely in size. They are starchier and drier than
sweet potatoes and rarely found in local grocery stores.

Why Do People Confuse Them?

So much confusion surrounds the terms sweet potatoes and yams.

Both names are used interchangeably and often mislabeled in supermarkets.

Yet, they are completely different vegetables.

A few reasons can explain how this mix-up happened.

Enslaved Africans brought to the US called the local sweet potato “nyami,” which translates to “yam” in English. This is because it reminded them of true yams, a food staple they knew in Africa.

In addition, the darker-skinned, orange-fleshed sweet potato variety was only introduced to the US several decades ago. In order to set it apart from paler-skinned sweet potatoes, producers labeled them “yams.”

The term “yam” is now more of a marketing term for producers to distinguish between the two types of sweet potatoes.

Most vegetables labeled as a “yam” in US supermarkets are actually just a variety of sweet potato.

Summary:
Confusion between sweet potatoes and yams arose when US producers began using
the African term “nyami,” which translates to “yam,” to distinguish between
different varieties of sweet potatoes.

They Are Prepared and Eaten Differently

Both sweet potatoes and yams are very versatile. They can be prepared by boiling, steaming, roasting or frying.

The sweet potato is more commonly found in US supermarkets, so as you’d expect, it is used in a wider range of traditional Western dishes, both sweet and savory.

It is most often baked, mashed or roasted. It is commonly used to make sweet potato fries, an alternative to baked or mashed potatoes. It can also be puréed and used in soups and desserts.

As a staple on the Thanksgiving table, it’s most often served as a sweet potato casserole with marshmallows or sugar or made into a sweet potato pie.

On the other hand, true yams are rarely found in Western supermarkets. However, they are a staple food in other countries, particularly those in Africa.

Their long shelf life allows them to be a steady food source during times of poor harvest (3Trusted Source).

In Africa, they are most often boiled, roasted or fried. Purple yams are more commonly found in Japan, Indonesia, Vietnam and the Philippines and often used in desserts.

Yams can be bought in a number of forms, including whole, powder or flour and as a supplement.

Yam flour is available in the West from grocers specializing in African products. It can be used to make a dough that is served as a side with stews or casseroles. It can also be used similarly to instant mashed potatoes.

Wild yam powder can be found in some health food and supplement stores under various names. These include wild Mexican yam, colic root or Chinese yam.

Summary:
Both sweet potatoes and yams are boiled, roasted or fried. Sweet potatoes are
used to make fries, pies, soups and casseroles. Yams are more commonly found in
the West as a powder or health supplement.

Their Nutrient Content Varies

A raw sweet potato contains water (77%), carbohydrates (20.1%), protein (1.6%), fiber (3%) and almost no fat (4).

In comparison, a raw yam contains water (70%), carbohydrates (24%), protein (1.5%), fiber (4%) and almost no fat (5).

A 3.5-ounce (100-gram) serving of baked sweet potato with the skin on contains (4):

• Calories: 90
• Carbohydrates: 20.7 grams
• Dietary
  fiber: 3.3 grams
• Fat: 0.2 grams
• Protein: 2 grams
• Vitamin A: 384% DV
• Vitamin C: 33% DV
• Vitamin B1 (Thiamine): 7% DV
• Vitamin B2 (Riboflavin): 6% DV
• Vitamin B3 (Niacin): 7% DV
• Vitamin B5 (Pantothenic acid): 9% DV
• Vitamin B6 (Pyridoxine): 14% DV
• Iron: 4% DV
• Magnesium: 7% DV
• Phosphorus: 5% DV
• Potassium: 14% DV
• Copper: 8% DV
• Manganese: 25% DV

A 3.5-ounce (100-gram) serving of boiled or baked yam contains (5):

• Calories: 116
• Carbohydrates: 27.5 grams
• Dietary fiber: 3.9 grams
• Fat: 0.1 grams
• Protein: 1.5 grams
• Vitamin A: 2% DV
• Vitamin C: 20% DV
• Vitamin B1 (Thiamine): 6% DV
• Vitamin B2 (Riboflavin): 2% DV
• Vitamin B3 (Niacin): 3% DV
• Vitamin B5 (Pantothenic acid): 3% DV
• Vitamin B6 (Pyridoxine): 11% DV
• Iron: 3% DV
• Magnesium: 5% DV
• Phosphorus: 5% DV
• Potassium: 19% DV
• Copper: 8% DV
• Manganese: 19% DV

Sweet potatoes tend to have slightly fewer calories per serving than yams. They also contain a bit more vitamin C and more than triple the amount of beta-carotene, which converts to vitamin A in the body.

In fact, one 3.5-ounce (100-gram) serving of sweet potato will supply you with almost all of your daily recommended amount of vitamin A, which is important for normal vision and the immune system (4).

Both sweet potatoes and yams have decent amounts of other micronutrients, such as B vitamins, which are vital for many bodily functions, including producing energy and creating DNA.

It is also important to consider the glycemic index (GI) of each. The GI of a food gives an idea of how slowly or quickly it impacts your blood sugar levels.

GI is measured on a scale of 0–100. A food has a low GI if it causes blood sugars to rise slowly, whereas a high GI food causes blood sugars to rise quickly.

Cooking and preparation methods can cause a food’s GI to vary. For example, sweet potatoes have a medium-to-high GI, varying from 44–96, whereas yams have a low-to-high GI, ranging from 35–77 (6).

Boiling, rather than baking, frying or roasting, is linked to a lower GI (7Trusted Source).Summary:
Sweet potatoes are lower in calories and higher in beta-carotene and vitamin C
than yams. Yams have slightly more potassium and manganese. They both contain
decent amounts of B vitamins.