Potatoes, Sweet Potatoes, and Yams: What’s the Difference? (2024)
Above: Yam specimen
What you know asyams are most likely not actually yams.In fact, your “classic” potatoes, sweet potatoes, and yams are all in different plant families. However, they all are widely cultivated for their nutritious starchy belowground plant structures called “tubers.”Tubers function as storage organs for the plants, providing energy for regrowth(the “eyes” or sprouting buds of your potatoes when they sit in your kitchen for too long).Potatoes and yams technically havemodified belowground stems (“stem tubers”) while sweet potatoes have “root tubers.”
Yamis a common name for several vine species in the genusDioscorea(plant family:Dioscoreaceae).They are monocots (related to grasses and lilies). Yams are widely cultivated worldwide, especially in West Africa, where 95% of the crop is harvested. Yams can be stored for very long periods of time, making them an important crop for seasons when food isin short supply.Yam tubers can be as large as five feet long!
Sweet potatoes refer to a vine species (Ipomoeabatatas)inthe morning glory family (Convolvulaceae).This species is likely what is on your Thanksgiving dinner table.In the United States and Canada, sweet potatoes are often(confusingly)referred to as “yams.”But sweet potatoes are notevenclosely related to yams.As such, the USDA requires any label with “yam” to also include “sweet potato.”So why are sweet potatoes sometimes confusingly called yams? The name probably dates back to colonial times whenslaves from Africanoted the similarities between some varieties of sweet potatoes to yams in Africa.
Above: Potato specimen
And last—the “classic” potato,Solanumtuberosum. Potatoes belong to the nightshade family (Solanaceace), which also includes many other important crops like peppers, tomatoes, tomatillos, eggplant, tobacco, and more.Critical to the world’s food supply, potatoes are the fourth most farmed crop.Potatoes are only distantly related to sweet potatoes.They are also called “spuds,” which probably originated centuries ago from a term for a spade used to dig holes to plant potatoes. Having been cultivated for centuries, there arethousands ofpotato varieties worldwide.The cultivated species was domesticated from wild relative potatospecies in South America (Peru) 7,000–10,000 yearsago.Interestingly, discoveries onthe origin of potatoes was based on DNA from200-year-oldherbarium specimens! Similarly, the origin of the Irish Potato Famine (caused by potato late blight from a fungal pathogen) was also discovered usingfungalDNA extracted from 160+ year old herbarium specimens!
Botanists at Carnegie Museum of Natural History share pieces of the herbarium’s historical hidden collection on the dates they were discovered or collected. Check back for more!
Yams and sweet potatoes differ in flavor and appearance, and they are not related. Sweet potatoes are in the morning glory family, while yams belong to the lily family. Yams aren't as sweet as sweet potatoes, and they are starchier and drier. Their texture and flavor are more similar to potatoes or yuca.
A sweet potato is a root.Yams tend to be more cylindrical and have scaly, bark-like skin.Sweet potatoes tend to have a more tapered shape and may be firm or soft with thinner skin. Generally, sweet potatoes taste sweeter than yams.
"They are not related or even in the same plant family," Harvey said. "Sweet potatoes are considered storage roots and are grown from plant vine cuttings called slips.Yams are considered tubers and are grown from pieces of the tubers."
Though they can both be part of a healthy diet, sweet potatoes are generally healthier than regular potatoes, partly because of their incredibly high vitamin A content. Sweet potatoes are also lower on the glycemic index, meaning that they are less likely than regular potatoes to make your blood sugar spike.
When soft varieties were first grown commercially, there was a need to differentiate between the two. African slaves had already been calling the 'soft' sweet potatoes 'yams' because they resembled the yams in Africa. Thus, 'soft' sweet potatoes were referred to as 'yams' to distinguish them from the 'firm' varieties.
No, yams and sweet potatoes are not the same. Yams have rough, dark brown skin that is often compared to tree bark, and their flesh is dry and starchy like a regular potato. Sweet potatoes have smooth reddish skin, softer flesh (when cooked), and a sweet flavor.
Its high fibre content contributes to a glycemic index of 54, significantly lower than that of potatoes having a glycemic index of 80. This makes yam better suited for weight watchers, diabetics and those with heart disease as it does not create sharp increase in insulin response.
If you were to roast two different sweet potatoes and then taste them side by side, you might notice a small difference in taste. Some say that purple sweet potatoes are slightly sweeter. Others claim that they're less sweet, but have a creamier texture.
In the United States, the terms "yam" and "sweet potato" are used interchangeably, but they are completely different vegetables. Yams are starchy and have a rough, brown exterior. They can grow up to 45 feet long and are eaten in parts of Latin America, West Africa, the Caribbean, and Asia.
All potatoes can fit into a healthy diet, but purple potatoes, red potatoes, and sweet potatoes—which are often grouped with potatoes—stand out due to their high amounts of protective plant compounds and essential nutrients.
Boiled sweet potatoes affect blood sugar levels far less than other varieties, such as fried, roasted, or baked versions. Longer boiling times reduce the GI further. To support better blood sugar control, it's best to select healthy cooking methods and enjoy sweet potatoes in moderation.
Researchers are beginning to understand now how much chronic inflammation contributes to the development of chronic diseases such as diabetes and cancer. Sweet potatoes contain natural anti-inflammatory compounds that help to reduce inflammation in the body.
Both sweet potatoes and yams are nutritious, albeit completely different vegetables. They are both good to eat as a part of a healthy diet and neither is particularly nutritiously superior to the other. That being said, sweet potatoes contain more vitamin C, vitamin A, fiber, and protein.
Wash the potatoes well when you're ready to cook them. Don't store potatoes in the fridge. Raw potatoes have lots of starches, and the cold temperatures can turn the starches into sugars. This can make your potatoes turn sweeter and darker during cooking.
To understand the difference between yams and sweet potatoes, the botanical name plays a starring role. True yams belong to the genus Dioscorea. Sweet potatoes, on the other hand, belong to the genus Ipomea.
Sweet potatoes with orange flesh are richest in beta-carotene. Sweet potatoes with purple flesh are richer in anthocyanins. Beta-carotene and anthocyanins are naturally occurring plant “phyto” chemicals that give vegetables their bright colors.
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.
“Sweet potato, often associated with oven baked, roasted or mashed, can actually be consumed raw,” says Cox. But you'll want to grate the flesh first to make it more palatable: “Grated into a slaw, sweet potatoes are a super source of beta carotene, vitamin C and fibre.”
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