Did you know that yams (Dioscorea alata) and sweet potatoes (Ipomoea batatas) are two completely different vegetables? If you are surprised to learn this fact, you are not alone, as the names sweet potato and yams are often used interchangeably and also look very similar and are often mislabeled at grocery stores, especially in the western world, which leads to a lot of confusion.
Many westerners have likely never tasted a yam before, as they are much more popular in and prevalent in the culinary traditions of African and Asian countries and are hard to find in the states.
Both sweet potatoes and yams form underground as tubers and they are both healthy additions to most any diet, although their health benefits and nutritional values are somewhat different from each other. Though sweet potatoes and yams are both root vegetables that are highly nutritious in their own way, the similarities between the two basically end right there.
Though often confused, sweet potatoes and yams come from plants that are not even closely related. Sweet potatoes are dicots, or plants that contain dual embryonic seed leaves. Sweet potatoes are a member of the morning glory plant family, or the Convolvulacea family. Yams, on the other hand, are monocots, meaning they only possess one embryonic seed leaf. Yams are from the yam family, which is also called the Dioscoreaceae family.
In the west, sweet potatoes are often mislabeled as yams, but the two tuberous vegetables are actually quite different. In this article, we break down the differences between the two tubers, then we’ll discuss the two main reasons why they are so often confused and mislabled in the US.
What Are Sweet Potatoes?
There are over 400 varieties of sweet potatoes. The various sweet potato varieties have skins ranging from a reddish brown or orangeish brown, to a soft white, beige, or tan, to even purple-skinned varieties. The flesh can be either orange, white, or purple as well. Sweet potato varieties fall into two distinct categories, which are firm and soft. After being cooked, firm varieties of sweet potato stay very firm, while soft varieties become both soft and moist, perfect for cooking and eating.
What Are Yams?
There are over 600 different yam varieties, 95% of which are native to Africa. The other five percent hail from Asian countries. The various yam varieties can vary greatly in size. Some grow to about the same size as a small sweet potato, while other varieties can produce massive crops as large as 130 pounds. Yams usually have white or light beige flesh and skin that is brown and stringy, similar to the outer shell of a coconut. Yams have flesh that is much more starchy and much drier than the flesh of sweet potatoes. Sweet potato flesh, especially the soft varieties, is tender, sweet, and moist.
Two Reasons for the Confusion
There are two distinct reasons why the names of the two tuber vegetables are so often confused in the US. First, African slaves began calling sweet potatoes yams because the soft sweet potatoes that they found in the US resembled the yams they would cook and eat in their homeland. To distinguish the soft varieties of sweet potatoes from the hard varieties, African slaves would refer to them as yams.
In Louisiana, sweet potato farmers didn’t start cultivating soft sweet potato varieties until the 1930’s. They decided to market the new varieties of sweet potatoes as yams in order to distinguish them from the hard varieties, as well as the produce that was brought into Louisiana markets from other states.
So, the name yams spread throughout the south and beyond due to two different origins of misinformation. Calling sweet potatoes yams dates back to two different misidentifications, both of which originated centuries ago in American history, and continue to cause confusion to this day.
Basic Information on Yams and the Three Different Types of Sweet Potatoes
Yams, in comparison to sweet potatoes, are less sweet and moist, and more similar to the yucca plant in both flavor and texture. Yams have a tough, bumpy sin that is dark brown and textured like the outer shell of a coconut, or like a tree trunk. Their flesh is starchy instead of sweet, with a flavor similar to the common white russet potatoes, but with a more fibrous texture. Yams have more complex carbs than sweet potatoes and are commonly prepared by boiling. Yams have a rather neutral flavor, and are common features of Caribbean and West African cuisines, where they are commonly served with braised meats as a side dish. They are quite hard to find in America, as they are not a big part of our culinary traditions. Real yams are usually not available in American grocery stores, but can sometimes be found in international grocery stores or specialty stores.
Orange Sweet Potatoes
Orange sweet potatoes are the variety readers are most likely to be familiar with from their own kitchens, where we use them in everyday dishes like french fries or baked sweet potatoes as well as to create classic Thanksgiving sides and pie. Within the category of orange sweet potatoes, the individual varieties are similar enough that they can be interchanged with one another without an issue, as the differences that exist in their level of sweetness, amount of moisture, and the way they taste are subtle.
Beauregard: These potatoes are from Louisiana, where they are still grown today. They have brown skin and a deeper sweetness than other types.
Garnet: This sweet potato variety has a red skin, and the flesh of the potatoes tastes more like that of a pumpkin than other varieties of sweet potato do.
Jewel: In this variety from California, the skin is coppery orange while the flesh is earthy, with a mild, sweet taste.
White Sweet Potatoes
Sweet potatoes resemble the standard white baking potato that resembles russet potatoes. However, unlike russets, white sweet potatoes offer many of the same nutrients as orange ones do. They don’t have quite as much beta carotene as orange sweet potatoes, though.
White sweet potatoes also vary from the orange variety in their texture, which is a bit drier. When the potatoes are roasted, they get more chew and solidity than in other preparations due to the reduced moisture level they offer. Braising white sweet potatoes over low heat for a long period of time results in a dish where the potatoes feel creamy and silky while still keeping the shape they’ve been sliced or diced into..
This makes white sweet potatoes really tasty when they’re used in dishes like gnocchi that allow the chef to adjust the moisture level of the dish with a bit of flexibility and freedom. In addition to gnocchi, white sweet potatoes work exceptionally well with acidic sauces such as the South American sauce that’s similar to pesto called chimichurri.
Purple Sweet Potatoes
In addition to their vivid and unexpected color, purple sweet potatoes pack a punch of the flavonoid called anthocyanins. You’ll find anthocyanins in blueberries, where they’re responsible for the antioxidants these fruits contain as well as their trademark indigo shade. The color of purple sweet potatoes is likely to bleed out of the vegetables when cooked.
Okinawan: The Hawaiian purple sweet potato called Okinawan produces potatoes whose flesh is spotted and streaked with purple instead of having completely transformed. The color of Okinawan purple sweet potatoes is susceptible to bleeding out of the potatoes as they cook. However, this can be avoided by preparing Okinawan potatoes by roasting, frying, or sautéeing them.
Stokes: This purple sweet potato is the most popular with consumers. Stokes sweet potatoes have a sweet flavor that’s nutty, like chestnut.
Nutritional Values and Health Benefits of Yams and Sweet Potatoes
Despite their similarities across various categories, yams and sweet potatoes still have plenty of areas where they differ from one another. Unsurprisingly, their nutritional content is no different. In the information below, statistics for sweet potatoes and yams are provided for the raw vegetables unless otherwise specified.
- Both yams and sweet potatoes are almost completely free of fat.
- Raw sweet potatoes have seven percent more water per serving than raw yams do.
- When it comes to protein, sweet potatoes have just slightly more than raw yams.
- Both vegetables are low in fiber, with sweet potatoes containing just a bit less than yams
- The carbohydrate content of yams is three percent higher than that of sweet potatoes in each serving.
- Sweet potatoes are a bit lower in calories than yams are.
- Yams have more potassium and manganese than yams. These nutrients help the body build healthy bones as well as supporting the heart, metabolic function, and helping the body continue to grow and create healthy cells.
- Sweet potatoes offer triple the amount of beta carotene that’s contained in an average yams. Beta carotene is important because inside the human body, beta carotene converts to Vitamin A, which promotes healthy vision and immune system function. Even though sweet potatoes provide less beta carotene than yams, one serving of 3.35 ounces of 100 grams of sweet potato gives all the vitamin A a person needs to achieve their recommended daily value.
- Both vegetables provide a substantial serving of B vitamins, which the body uses in energy production as well as to make DNA.
Precautions for Yams and Sweet Potatoes
Though both yams and sweet potatoes are generally thought of as healthy foods that are good additions to diets, each comes with an adverse effect that consumers should be aware of. Sweet potatoes contain considerably high levels of oxalates, which are naturally occurring compounds present in a variety of foods. These naturally occurring compounds usually cause no serious damage to most people, but for people who are especially susceptible to kidney stones, oxalate intake is a serious concern. If your body is prone to kidney stone formation, you should be especially careful about consuming oxalate-rich foods, such as sweet potatoes, as the oxalates present in certain fruits and vegetables, can build up in your system and form stones.
Sweet potatoes are safe to eat in both cooked and raw forms, but many yam varieties are only safe to consume after they are cooked. This is due to naturally forming plant proteins that occur naturally in yams which can be toxic and can cause sickness if they are eaten raw. Peeling and cooking these yam varieties removes any toxic elements and makes them safe for consumption.
Yams and sweet potatoes are completely different root vegetables that have been mistakenly mislabled for ages, though they are both tasty, nutritious and resourceful vegetables that are great additions to most diets. Sweet potatoes are easier to find in America, and are slightly more nutritious than yams, which are more common in African and Asian countries. If you enjoy sweeter vegetables with a smoother, moister texture, stick with sweet potatoes. If you like starchier vegetables with drier textures, you may really enjoy adding yams to your diet, though you may have to grow them yourself if you can’t find them in an international grocery store in your area. Sweet potatoes and yams are both good choices for a healthy nutrient-rich diet.