True yams are the starchy tubers of many Dioscorea species. They should not be confused with sweet potatoes, which are sometimes referred to as yams in parts of North America.
Yams are common in the Caribbean, Latin America, and Africa. True yams are toxic in their raw state, but cooking of any form removes the toxins and makes them harmless. They're generally sold in chunks sealed in plastic, and have a light-coloured interior and dark skin.
There are a few varieties of cultivated yam. These include:
- White/yellow yam (D. rotundata/cayennensis): Native to Africa; most widely-cultivated variety
- Purple yam (D. alata), also called water yam: flesh ranges from purple to white or cream-colored
- Chinese yam (D. polystachya)
They can be used in any sweet potato recipe.