GOOD CARBS FOOD FACTS
Living in Australia, my exposure to the celebration of Thanksgiving was through the American TV shows I watched growing up. I know turkey plays a central role on the thanksgiving table, but I also know candied yams are a traditional side-dish. As thanksgiving is coming, it got me thinking about yams, as I don’t think I’ve ever eaten them.
But wait, I’ve eaten sweet potato and isn’t that the same thing? No. Although the terms are used interchangeably in North America, sweet potatoes (ipomoea batatas) and true yams (Dioscoreaceae) are different things altogether. Although they are both root vegetables (tubers), they aren’t even in the same botanical family. Yams are part of the lily family. Candied yams enjoyed at Thanksgiving aren’t yams at all but sweet potato.
Most yams are grown in Africa and they’re also native to Asia. Yams are cylindrical and come in different sizes, including some that can be up to 25kg each! The most common African species have dark brown, rough skin and white (Dioscorea rotundata) or yellow flesh (dioscorea cayennensis). The white yam was (dioscorea alata) first cultivated in Asia and is known as uhi in Hawaii. The Chinese yam is Dioscorea polystachya. In New Zealand and Polynesia Oxalis tuberosa are referred to as yams, or Oca in Spanish and are only 2-3 cm long.
Yams are starchier and drier than sweet potato and typically ground into a paste known in Africa as Iyan, but they can be cooked in many ways. Most yams need to be cooked as eating them raw can cause illness. Boiling, frying or roasting are common, and similar to other starchy vegetables they provide a neutral base on which to serve savoury or sweet dishes. If you’d like to give them a try, find them at specialty greengrocers and perhaps make this African Yam Stew or Yam fries.
Nutritionally, yams have high water content, are low in protein, virtually fat-free and contain around 27% carbohydrate of which most is starch. They are a good source of potassium, fibre and also contain vitamin B6 and vitamin C. The yellow flesh varieties are loaded with carotenoid antioxidants. The glycemic index (GI) varies by species. The common African species are medium to high GI, while the New Zealand and Chinese species are low GI.
Source: USDA, 2020
Nicole Senior is an Accredited Practising Dietitian, author, consultant, cook and food enthusiast who strives to make sense of nutrition science and delights in making healthy food delicious.
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