A Visual Guide to Yams and Sweet Potatoes (plus How They Fit Into a Primal Eating Plan)
by Mark Sisson
Mark's Daily Apple
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Quick. What's a suitable, Primal source of post-workout carbohydrates? If the title of this post and the picture to the right didn't give you a hint then ask your nearest Primal enthusiast and they'll tell you without batting an eye, yams and sweet potatoes. If, for whatever reason, you need some extra carbs yams and sweet potatoes is the answer. Everyone knows this, but is it true?
That's what I'll be exploring in today's post. But first, what are yams and how do they differ from sweet potatoes?
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 my readers — even the active ones including more carbohydrate in their diets — 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, or Ipomoea batata, 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 Polyenesia, 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. Now that's a carb refeed!
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 you picture when you think of a sweet potato — light tan skin, slightly yellow interior. It's creamy, almost like a Yukon gold potato, and slightly sweet.
Basic sweet potatoes are strong sources of beta-carotene, manganese, and copper. A small one has 22g carbs and 3g fiber (food for your gut flora), making it the perfect post-workout snack. Amazing with cinnamon.
Garnet, Jewel, Beauregard: these are the orange fleshed, reddish-brownish-orangish skinned sweet potatoes masquerading as yams. They're even more common than the standard sweet potato, sweeter, and contain a bit more water (you can hear it escape when you bake them). These guys cook surprisingly well in a microwave. Pop 'em in, heat, mash lightly, load with butter and enjoy. You can expect to see quite a bit of them this coming Thanksgiving.
Okinawan Purple Sweet Potato
These are my current favorites. They are white skinned with a deep, brilliant purple interior that becomes velvety smooth and incredibly sweet when baked. Even better, 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. According to this entirely unbiased source, Okinawan sweet potatoes contain 150% more anthocyanins than the same amount of blueberries. That sounds reasonable, and a good general rule is the purpler the potato (or bluer the berry), the greater the anthocyanin content.
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; protection against acetaminophen-induced liver damage in mice. In human males with borderline hepatitis, a beverage infused with purple sweet potato anthocyanins significantly decreased the serum levels of hepatic biomarkers. Plus, the long-lived, fairly healthy Okinawans have traditionally used Okinawan purple sweet potatoes as a staple food. All the evidence seems to support their status as a healthy, delicious tuber.
There's another variety that looks extremely similar but has a lightly violet interior streaked with white. It's starchier and far drier than the Okinawans, and it doesn't taste nearly as good. If you go looking for Okinawan potatoes in Asian supermarkets (which is the only place I've been able to find them consistently), inspect them carefully before buying. I once saw an old Chinese woman at one of these places snap the end of each potato off with her fingernail to check the color inside; this method works well, is relatively inconspicuous, and it's a good way to make sure you're getting the true Okinawan sweet potato. Just look for the deep purple flesh.
Japanese Sweet Potato, or Satsumaimo
Another Asian market mainstay is the satsumaimo, or Japanese sweet potato (can you tell I've been availing myself of the local ethnic markets?). I actually don't care for this one. It's just too sweet. Once you get it into the oven and the sugars start caramelizing, it becomes way too much for my palate. It's honestly like eating dessert, which probably makes it sound pretty alluring for some. Look for purplish skin with a light interior (that turns golden brown with caramelizing). Give it a shot with some salty butter and maybe a dash of cinnamon and nutmeg if you want something sweet.
November 19, 2010
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