In the United States, most tubers sold as yams are actually members of the sweet potato family. Your Garnets, your Jewels, the “yams” with the rich orange flesh and reddish-brown exterior, are, botanically, sweet potatoes. In fact, it’s quite likely that the vast majority of people have never tasted a true yam. The reason for this discrepancy is simple marketing: back in the mid-20th century, when orange-fleshed sweet potatoes were introduced into the United States, they were labeled “yams” to avoid confusion with the common white-fleshed sweet potato Americans were already enjoying. “Yam” was derived either from the Spanish “name” or Portuguese “inhame,” both of which come from the Wolof word “nyam,” which means “to sample” or “to taste.” Another African language uses “yamyam” for “to chew,” which should give you some idea of the starchy tuber’s importance in local diets – as well as the level of mastication required for its consumption.
Sweet potatoes are native to South America, where they were domesticated at least 5000 years ago. They’re also common in Polynesia, and radio carbon dating of sweet potato remains in the Cook Islands places them at 1000 AD, with most researchers figuring they date back to at least 700 AD. The Peruvian Quechua word for sweet potato is kumar, while it’s called the remarkably similar kumara in Polynesia, prompting speculation that early South American voyagers actually introduced the tuber to the South Pacific. At any rate, they’re delicious, they’re eaten everywhere, and they have a lengthy tradition of being consumed by healthy people.
Real yams hail from the Dioscorea family of perennial herbaceous vines and include dozens of varieties, some of which grow to over eight feet long and weigh nearly two hundred pounds.
Anyway, since most of us will be coming across sweet potatoes either disguised as yams or labeled correctly, let’s direct our attention to the various properties of the different sweet potato varieties.
The Classic Sweet Potato
This is probably what most of us picture when we think of a sweet potato - light, tan skin, slightly yellow interior. Creamy, and slightly sweet. Basic sweet potatoes are strong sources of beta-carotene, manganese, and copper and a good amount of fiber.
Yam
Orange-fleshed, red/brown/orange skinned sweet potato masquerading as a yam. They're even more common than the standard sweet potato, sweeter with a bit more water content.
The Okinawan Purple Sweet Potato
White-skinned, with a brilliant purple interior that becomes velvety smooth and incredibly sweet when baked. The purple pigment is due to the vast numbers of anthocyanins - the very same beneficial antioxidant pigments that provide blueberries their brilliant color and health benefits. Several studies show potential benefits to purple sweet potato anthocyanins: suppression of mouse brain inflammation, alleviation of brain aging, reduction in cognitive deficits, inflammation and oxidative damage in aging mouse brains, potential suppression of neurodegenerative cell death, as in Alzheimer's, as well as protection against acetaminophen-induced liver damage in mice.
Wow! I don't know about you, but I'm really interested in the Okinawan!
As we all know, foods aren’t just their macronutrient composition. Micronutrient matters as well, and it’s also important to see the food as exactly that: whole food, a package deal. You might, for example, suppose that starchy sweet potatoes are absolutely horrible for patients with diabetes. But sweet potatoes aren’t just starch; caiapo, an extract of the standard sweet potato, was given to type 2 diabetics. After five months, they displayed greater glucose control. Another study on diabetic patients had similar results. It’s important to note that these were using non-caloric extracts, as opposed to actual sweet potatoes, but another study found that actual sweet potatoes were beneficial to diabetic rats. Things might be different for diabetics eating actual sweet potatoes (starch included), but I think it’s pretty clear that healthy people can eat them freely.
There are thousands of varieties of sweet potatoes and yams. It would be
impossible to document them all, and foolish to try. Just know this: they are healthy, tasty, safe sources of starch that people have been eating for a long, long time. If you’re trying to lose weight, keeping your intake low is probably best. But these starchy tubers are a welcome addition only every once and awhile - in moderation when they are added. I especially love sweet potato fries.
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