Difference Between Sweet Potatoes and Yams
True yams and sweet potatoes are completely different plants. What American grocery stores label as 'yams' are actually just orange-fleshed sweet potatoes. Real yams are starchy, dry, African/Asian tubers rarely found in US stores. Sweet potatoes are sweeter, moister, and come in orange, white, or purple varieties.
Key Takeaways
- The confusion started in the mid-20th century when orange-fleshed sweet potatoes were introduced to the US.
- Japanese sweet potatoes have purple skin and white flesh - still sweet potatoes, not yams.
- Canned 'yams' in the US are always sweet potatoes, typically the orange-fleshed Beauregard or Garnet varieties.
Explanation
The confusion started in the mid-20th century when orange-fleshed sweet potatoes were introduced to the US. To distinguish them from the existing white-fleshed varieties, producers marketed them as 'yams' (from the African word 'nyami'). The USDA now requires products labeled 'yam' to also say 'sweet potato,' but the misnaming persists.
True yams (genus Dioscorea) are native to Africa and Asia. They have rough, bark-like skin, can grow over 100 pounds, and have dry, starchy white or purple flesh. They're a staple food in Africa, the Caribbean, and parts of Asia. You'll typically only find real yams at international or African grocery stores in the US.
Sweet potatoes (genus Ipomoea) are native to Central and South America. They have thin, smooth skin and come in many varieties: orange-fleshed ('yams' in stores), white-fleshed (drier, less sweet), and purple-fleshed (Okinawan). All sweet potatoes are nutritious, rich in beta-carotene (orange varieties), fiber, and vitamins.
Nutritionally, orange sweet potatoes contain extraordinary levels of beta-carotene: one medium baked sweet potato provides over 400% of the daily recommended vitamin A intake. They also deliver 3.8 grams of fiber, 2 grams of protein, and about 103 calories. True yams, by contrast, have minimal beta-carotene but provide more potassium (816 mg per cup versus 448 mg for sweet potatoes) and significantly more calories at roughly 158 per cup due to their higher starch content.
Cooking methods affect each differently. Sweet potatoes become sweeter when baked because the enzyme amylase converts starches to maltose sugars between 135°F and 170°F during slow heating. Baking at 350°F for 45-60 minutes maximizes this conversion. True yams hold their shape better in soups and stews because their starch structure resists breaking down. In West African cuisine, yams are often boiled and pounded into fufu, a starchy side dish with a texture similar to mashed potatoes but much denser.
Things to Know
- Japanese sweet potatoes have purple skin and white flesh - still sweet potatoes, not yams.
- Canned 'yams' in the US are always sweet potatoes, typically the orange-fleshed Beauregard or Garnet varieties.
- Real yams are rarely eaten in the US but are essential to West African and Caribbean cuisines.
- The nutrition profiles differ: sweet potatoes have more sugar and beta-carotene; yams have more potassium and complex carbs.