A Visual Guide to Yams and Sweet Potatoes (plus How They Fit Into a Primal Eating Plan)
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.
Sweet Potatoes
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.
The “Yams”
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.
Yams
Dioscorea rotunda/cayenensis – The Common African Yam; “White Yam”; “Yellow Yam”
This is the true yam, with over 200 varieties in existence. Traditional preparation takes many forms, but the most common method is peeling and boiling. Fufu is mashed yam mixed with sauces, usually palm oil based. There’s also the practice of drying raw yam and smashing it into a powder, or flour, or, I dunno, maybe a big pile of starch granules (sound familiar?). This is called elubo. Though folks in the States and Europe rarely see it, it’s one of the most widely cultivated crops on the African continent, and by far the most popular yam in terms of sheer numbers. Look for it in African or Caribbean markets.
D. alata – The Purple Yam; “Water Yam”; “Winged Yam”
The purple yam was originally cultivated in Southeast Asia and is now the most widely distributed variety. It’s grown in Africa, Asia, the Pacific islands, the Caribbean, and it’s even wormed its way into the southern United States as a highly invasive marauding species. I suspect this may be the imposter I encountered when looking for Okinawan sweet potatoes, although the purple yam has its own benefits: one study found replacing rice with D. alata in the diets of postmenopausal women improved blood lipids (reduced LDL oxidation) and helped normalize sex hormones (increases in sex hormone binding globulin, estrone, and estradiol; a reduction in the total testosterone::SHBG ratio). A similar study with true sweet potatoes instead of yams did not have this effect. I’m not a postmenopausal woman, but maybe I’ll give it a shot next time.
D. opposita – “Chinese Yam”; Japanese “Mountain Yam”
This is cultivated in China, Japan, and Korea, but it’s made its way into the southern US, also as an invader (PDF) – though US Chinese yam plants don’t appear to bear any edible yams. Too bad. It’s one of the only true yams edible raw (the Japanese serve grated raw D. opposita after lightly soaking it in a vinegar-water solution to neutralize the oxalates in the skin). The Chinese, who call it shanyao, have used it as an herbal medicine for thousands of years in the treatment of liver and kidney disease. In rats, shanyao extract seems to decrease liver and kidney damage related to alcohol abuse and acetaminophen abuse. I’ve seen this in Asian supermarkets here in LA, but have never tried it myself. It’s quite tasty served alongside sashimi, however.
For all these tubers, my go-to method of cooking is to toss a handful in the oven at 400 degrees F and check on them after about an hour. Some people prick them a couple times before cooking, but I usually don’t. If you’re in a rush, wrap them in paper towels and heat them in the microwave for a couple minutes before finishing them in the oven. If they’re oozing goo (listen for the squeal of escaping steam) or soft to the touch, they’re probably ready. That goo burns, so make sure you use either foil or a cookie sheet to protect your oven. This method has served me well for any sweet potato or “yam” I’ve come across. Some may take a little longer, some a little shorter, but the poke, prod, and goo methods are reliable and field-tested.
They keep well in the fridge for up to a week, so active folks eating more carbs can make a bunch at once for easy refeeds. Just reheat in a 200 degree oven or eat cold right out of the fridge. You can also smash the cooked, chilled tubers into a flat pancake and fry that up with some butter, coconut oil, and cinnamon. Very tasty.
Traditionally, sweet potato and yam skins are removed before consumption, so I err on the side of caution and do the same. I doubt a bit of skin is going to hurt you, though, if you decide to eat it. Most of the anti-nutrients in potatoes can be found in the skin, and it seems logical to assume the same is true for yams and sweet potatoes.
Organic or conventional?
Generally, I opt for organic, but it may not matter as much with sweet potatoes. Sweet potatoes consistently show up with lower pesticide residues, especially when compared to normal potatoes. As always, though, the best is locally grown in rich soil. Big farms may have good soil and growing practices, but at least when you buy from small farms at farmers’ markets, you get to meet the grower and ask them about their farm. Conventionally grown or big-time organic tubers may be perfectly acceptable, but they’ll be missing key minerals and micronutrients if the soil they were grown in is deficient and depleted. Plus, I find small farms produce tastier stuff as a general rule.
Sweet Potato Leaves
Though I haven’t seen them in any LA stores, sweet potato leaves are apparently quite nutritious and commonly eaten in some African countries. This study (PDF) did the work for us, examining the nutritive and anti-nutritive properties of the leaves. Highlights include low levels of cyanide (30.24mg/100g), phytic acid (1.44mg/100g), and tannins (0.21mg/100g); high levels of magnesium (340mg/100g), calcium (28.44mg/100g), and manganese (4.65mg/100g). Oxalate content was pretty high, though, (308mg/100g), but half that of spinach (750mg/100g). These might be worth trying and treating like spinach or kale if you can get a hold of some.
Other Health Benefits
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, higher adiponectin, and lower fibrinogen. 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 – just look at the Kitavans, who eat a ton of yams and sweet potatoes.
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 (if you go for that kind of thing) that people have been eating for a long, long time. If you’re trying to lose weight, keeping your intake to the post-workout period is probably best. If you’re looking for a dense source of carbs, I can’t imagine a better option. Of course, always keep your total carb intake goals in mind if and when you add yams and sweet potatoes to your eating plan. For me, and I’d suspect most people reading, keeping carbs on the low end is high priority, and thus these starchy tubers are a welcome addition only every once and awhile and in moderation when they are added.
What do you think? Do you have a favorite sweet potato variety? Favorite preparation method? Are sweet potatoes part of your diet, and if so, how often do you eat them? Share your thoughts in the comment board and thanks for reading.
Photo Credit: Ganjin, deccanheffalump Flickr Photos
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Posted By: Mark Sisson
What about “Black Potatoes”?
I know purple foods generally have antioxidants/anthocyanins, but haven’t seen anything regarding black.
I love my sweet potatoes. I make ‘em 3 ways:
1. Slice & dice, season, and slow cook them in a wok with a little bit of olive oil.
2. Mash ‘em. A drop of milk, a bit of butter, and onion salt and i have one of my favorite complements to pork chops seasoned with marjoram.
3. Boil ‘em in the microwave. Scrub the skins but leave them wet, poke some holes in them with a fork, put them in a plastic shopping bag and tie the handles. Microwave on high for 5 minutes. (I learned this tip from my Auntie in Ireland)
Interesting! What’s your take on taro?
taro is my favorite tuber, too!
(i like the the big one better not the small ones)
My favorite way to cook sweet potato which my whole family loves. I chopped the washed sweet potato into small cubes (skin and all). I saute them in coconut oil with some chopped vidalia or sweet onion until they are soft and browned. Sort of like sweet potato homefries. The coconut oil is key…
I’m late to this post, FANTASTIC information. Thank you for sharing.
The thing to do with Japanese Sweet Potatoes (Satsumaimo): Cut them into fries, toss with your oil of choice, and bake into fries. (Salt optional).
They hold their shape much better than orange fleshed and the sweetness is perfect – not overwhelming like they are when you bake them whole.
I always leave the skins on. Sweet potatoes make great wedges smeared with fat and sprinkled with Slap ya Mama seasoning then baked on 200 degrees C for 40 mins turning every 10 mins. We love ‘em.
Hi Mark,
Great post! I frequently have to explain the yam/sw potato terminology to my cooking students. I love sweet potatoes and yams and they’ve been a staple in my diet for more than 20 years. I’ve never seen the purple sweet potatoes. I will not start hunting for them!;-)
Btw: I find that sweet potatoes and yams with a smaller diameter tend to have a better texture and flavor than ones that are fat around the middle. I tell my students they should be firm, smooth, unblemished, and not any bigger around than a a circle you make with your thumb and fingers.
Baking definitely makes them sweeter and more flavorful than boiling or steaming. Mashed (orange sweet potatoes) with lime juice (about 6 medium sweet potatoes + juice of 1/2 lime) makes an amazing side dish with butter, coconut oil, or macadamia nut butter on top at the table.
Happy dining,
Rachel
Paleo and primal eaters who want to get more sweet potatoes into their diets can replace mashed banana with baked, peeled, mashed sweet potato or “yam”in baked goods. So, where you see paleo almond flour or coconut flour banana bread, muffin, or pudding recipes, you can use these instead.
There’s research showing that sweet potatoes help control and lower A1C levels in diabetics.
Sweet potato greens can be cooked just like chard, and the stems are good too! No need to boil first. I prefer them to chard. Yum. I’m in Austin, TX and we have these growing right now locally in August.
There’s a restaurant here in Boulder called the West End Tavern. They serve sweet potato chips with a huge bowl of guac. My absolute favorite way to eat sweet potatoes these days. We also substitute sweet potato chips or fries for tortilla chips when we want nachos. Amazing! Since we’re still trying to lose weight, these are only an occasional indulgence.
I am faily new to Marks daily apple, and i have noticed that several times that Mark and many of his followers,keep commenting on cooking foods in a microwave oven,including this newsletter on yams/sweet potatoes.
Mark,surely with your views on healthy
eating, you would be aware that microwave cooking is very dangerous,and could lead to various ailments, including cancer, I would urge everyone to throw away their microwave ovens.
Bryan Barreto, Nottingham, England.
Kia Ora from New Zealand. We have about seven varieties of sweet potatoe in New Zealand. There’re actually about 1600 varieties in South America. There are also about 4000 varieties of potatoe. Their culture evolves around these vegetables. I mention this because research here might render many diverse and healthful sweet potatoe recipes not too mention medicinal uses as is the case with New Zealand Maori. The sweet potatoe can also be eaten raw. While I hadn’t seen all varieties eaten as such, I have seen the Japanese sweet potatoe eaten raw in New Zealand. Enjoyed the posts – Thank you.
I’m 15 years old, although I’m not overweight, I definitely want to lean up (: Anyway, my favorite ‘sweet potato’ would have to be the Okinawan potato – it’s so good. I eat more than I should though, I used to eat one a day, but i think I’ll cut back to half a potato after my workouts. I’m taking the 30 Day Primal Challenge so, best of luck to me & thank you so much for posting.
I made some really good sweet potato chips once…sliced thin with a mandolin and fried in grass fed beef tallow…seasoned with Cajun seasoning.
I use them in hash — fry up some chopped bacon w/ onions, cut the yam into bite size pieces and toss in the bacon/onion mix. I also throw in last night’s leftover meat (pork loin cut into chunks, roast chicken, whatever). Add a bit of apple pie spice (cinnamon, nutmeg, allspice), some sea salt & pepper and it’s an awesome, delicate blend of sweet and savory. You can do the same with apples in place of the yams.
The wife and I STILL don’t understand why it’s ok to eat sweet potatoes, but regular spuds are not cool. I just have faith and accept this, but my wife raves about them being basically the same thing. How do I persuade here?
“Regular spuds” are in the nightshade family while sweet potatoes and yams are in the morning glory family.
I have been told that our U.S. sweet potatoes are sweeter than yams, correct? Also, as a breast cancer survivor, I avoid these because I’ve been told they are estrogen-producing in our bodies? Correct?
I’ve been told that one is a member of the nightshade family…which one?
Thanks!
hi mark, just reading this article from the link on your weekend link post from nov. 20th, the sweet potato leaves are called 地瓜葉 or literally, sweet potato leaves in chinese and you should be able to get them in most chinese stores in LA. monterey park is full of them. they are great as a quick stir fry.
Are ALL of them about 22 grams of carbs and 3 grams of fiber for a small one? Or do they vary. Which are the lowest carb ones?
BTW, I grew up on Okinawa. We used to eat “on the economy” (off the military bases in local restaurants) but as far as I recall, I NEVER saw a purple sweet potato, ever.
Thanks so much for the info, you certainly did your homework. Glad to know what that we cleared up the confusion between yams and sweet potatoes.
in the uk the ones listed as ‘the yams’ are standard sweet potatoes. i cut them into 1 inch chunks, roast them til theyve got some colour,caramalised a little then mash with butter and full fat milk. roasting helps remove the water so the mash is thicker and the caramelisation adds much more flavour. i also slice them about 1 cm thick, put them in a pan slightly over lapping so the whole pan is covered by a single layer and covered half to three quarters with stock,4 tablespoons olive oil , a few bashed garlic cloves, fresh rosemary sprigs and thyme, put the lid on and steam until cooked. try this 2nd method with white potatoes also. serve with grilled (or broiled if you’re in the US) lamb or pork chops marinated in more garlic, olive oil and rosemary. add the lamb/pork fat into any left over stock from the potatoes for a nice gravy. yum yum pigs (or lambs) bum.
Okinawan sweet potato IS so delicious. Just picked up a box from Costco here in Hawaii
Didn’t realize they had more antioxidants as blueberries. Good to know!
Could someone please comment on eating the skins of sweet potatoes? I always do that but this article made mention of anti-nutrients, without further explanation. What exactly makes it dangerous to eat the skins?
I’d like to hear the answer to that, too. I ate my yam last night, skin and all.
Mark, interested to hear your thoughts on the post-workout eating window.
I’ve heard 20 minutes, 1 hour, 2 hours.
Also worth noting, I get home after a lifting workout, eat and then go to bed shortly afterward. Last night, I had a yam with unsalted organic butter and six strips of bacon. The idea keeps nagging me that it’s bad for me to eat, then be in bed about 30 minutes later.
Thoughts?
I suggest removing the skin before eating. I think the skins are irritating to the digestive system. Sometimes they actually taste moldy or just funky. Anti nutrients interfere w/nutrient absorption. Many are bitter tasting too.
For fantastic flavor, choose sweet potatoes and American “yams” that you can wrap your fingers around. Wider ones tend to be tough and fibrous. Rinse, scrub, place on a dry baking sheet (no foil, no oil, no water). Bake at 400 degrees F for about 1 hour or until squishy soft, turning them over after 30 minutes to caramelize both sides.
Remove skin, mash with a little raw butter or coconut oil, add juice from finely grated, squeezed fresh ginger root; squeeze of lime juice is also good. Really delish! (for more recipes and amounts see my paleo book, The Garden of Eating)
My local store doesn’t know the difference either.
Here’s something I found interesting on
inflammationfactor.com/look-up-if-ratings
Sweet Potatoes have a really high anti-inflammatory rating and Potatoes have a really low rating.
She doesn’t list yams.
Thank you for the recipe on cooking the yam leaves, I grow the orange yams, and they are very delicious, cooked any way! Will now try cooking the leaves.
I cook the orange yam called Jewel, or beauregard, I love them any way you cook them. I grow them in my garden. I will now try cooking the leaves, as per the the person who was in the peace corps, and will saute in butter, as I am not fond of coconut oil.
Those Japanese sweet potatoes are the only ones available down in costa rica where I live. But they are delicious roasted with olive oil and spices and dipped in Dijon!