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17 Nov

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.


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

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Are sweet potatoes healthier than regular potatoes?

    William wrote on March 7th, 2012
  2. Thank you for such a informative and great article. I have noticed that some of my Tongan (South Pacific Island/Polynesia) language derives from Spanish just like the word Kumar is Kumala. We have a limited alphabet and replace r with l, j with s, and most words end in a vowel a, e, i, o, u but never y since it’s not in our alphabet.

    MaLiA wrote on March 25th, 2012
  3. I had Okinawan sweet potatoes when I was in Maui last year. They were absolutely one of the best things I have ever tasted! I wish they were readily available here – I live in the middle of nowhere, so my selection of “exotic” foods is pretty depressing. :(

    Megan Tidball wrote on April 4th, 2012
  4. Back home in Ethiopia we just cook sweet potato in plenty of water and after cooked you peel the skin and eat it. mostly used as a snack as TEff injera is the main food. Do you guys know what TEFFis? another great food which should be introduced to the world as great food,

    Judi wrote on April 7th, 2012
  5. Thanks for a great article on the differences between sweet potatoes and yams. the thing that I’m having the hardest time finding out is the nutritional info on the “yam” Are the carbs the same as the sweet potato or do they fall under the yam nutrition profile. I buy the deep orange with the reddy brown outside and always thought it was a true yam. Now I’m confused!

    Tamara Knight wrote on April 19th, 2012
  6. Peel them, boil them, mash them with butter, some sea salt and some yogurt or milk – them I put them on top of a 4 egg omelet and eat it with some sauerkraut and mustard – sometimes I put some sardines on as well

    charles grashow wrote on May 12th, 2012
    • i actually mix a little sauerkraut and juice with my mashed sweet potatoe, and a sprinkle of hempseeds. i love sweet and sour……..yummy.

      Elisabeth wrote on February 2nd, 2013
  7. I love the Portuguese yams (inhames). I boil them whole, then slice them into about 1/4 inch slices and fry them in olive oil, garlic, and crushed red pepper (not the dry flakes from the spice dept). Unbelievably good. There are Portuguese markets in southeastern Massachusetts that have them, about an hour and a half drive from where I live, I’m not sure where to get them elsewhere though.

    Eric wrote on July 5th, 2012
  8. Do yams belong to the nightshade family? I heard nightshade foods can be toxic to certain sensitive people.

    Jane wrote on July 5th, 2012
  9. I use them in everything but as sitting here right now.. I made myself a creamed yam soup with some cheese.. omgs yummy.

    Anne wrote on October 17th, 2012
  10. Well, finally an answer to my question “what is the difference between a yam and a sweet potato?” I guess I’ll just order sweet potatoes now. Thanks for your very informative data.

    ralph wrote on January 1st, 2013
  11. I was recently gifted a large bag of sweet potato greens & was extremely delighted with them both raw & cooked. They are very mild, slightly sweet & have a spongy texture that made a soft delicate addition to salad. When added to my chili they soaked up & enhanced all the flavors without wilting & losing that amazing texture.

    Anne Marie wrote on January 1st, 2013
  12. Thanks for this article Mark! It has clarifies a lot. Me and my family have had a debate for years over what a sweet potato and yam are. Im excited to check out the local asian markets to find some Okinawan purple sweet potatoes!

    Katlyn wrote on January 4th, 2013
  13. I love sweet potatoes and yams especially. I never knew there were so many other kind of different potatoes! Do you have idea what kind of potatoes are used mainly in making normal potato chips?

    James Tyler wrote on February 23rd, 2013
  14. i bought two real yams from a african grocery stand but only tried one kind so far, and it tasted exceedly bitter , did i do something wrong or is it suppose to be this bitter, i thought yams are sweet

    gram42 wrote on May 31st, 2013
  15. Very interesting post! I do quite a lot of cross fit and so far was using fruits (massive amount of fruits) as my sole source of carb…So I’ll definitely start using yams in my diet.

    My question is: Why are yams or sweet potatoes considered primal but not standard potatoes?

    What is the scientific reason behind it? Nutritional content is different? Or is it simply a question of history and domestication?



    Max wrote on June 19th, 2013
  16. Whoa what an awesome article! I’m Japanese-American and I grew up eating all of those bad boys. The Japanese mountain yam (we call it tororo) is often ground up much like we grind fresh ginger. It becomes gooey and we pour a little soy sauce on this (or coconut aminos or tamari) and eat it with raw tuna and a raw quail egg (yamakake) and its heavenly. But beware, it will make your hands itch if you touch it so prepare with gloves!

    Also those purple Asian potatoes can be turned into flour and thus into baked goods. I know many in the primal/paleo communities want to avoid those carbs but I’m also a mom and giving my kids purple pancakes full of nutrients and the carbs their little active bodies need works wonders. Making asian style sandwiches on the go with the leftover pancakes with pickled veggies and some pork is also pretty amazing.

    Annie Kobayashi wrote on October 3rd, 2013
  17. My understanding is that standard sweet potatoes are extremely high in oxalates, not just the Japanese kind. Adding calcium citrate powder to mashed sweet potatoes adds some credence to this, as the texture gets gritty (presumably from calcium oxalate crystals). Shouldn’t people with hypercalciuria and kidney-stone formers avoid them, along with spinach and other high oxalate foods?

    Jenny wrote on November 10th, 2013
  18. I came across the ‘Perfect Health Diet’ which is a basic paleo type diet that advocates potatoes, sweet potatoes and white rice as “safe Starches” and that they can be included daily – mashed with a bit of apple cider vinegar and butter.

    I proceeded to do this in modest amounts each day and 3 weeks later found myself 3.5 kg heavier! They did say this could happen initially but I’m wondering how long ‘initially’ lasts for.

    I can see that your article suggests only yams/sweet potatoes and now and then.

    Is the PHD incorrect or could I just be intolerance (I am fructose intolerant according to a breath type test I had).

    Roz wrote on December 14th, 2013
  19. Thank you for the sweet potato & yam info. I was in a store in Houston, confused by the sweet potato & yam labeling. Actually, I think of the orange-inside kind when I hear “sweet potato”, but I wanted the healthiest potato. Thanks to your breakdown, I ended up picking the okinawan variety. :-)

    Stephanie wrote on February 19th, 2014
  20. You can get some nice sweet potato leaves by sticking toothpicks in a piece of sweet potato and rooting it in a glass or jar (toothpicks keep it from falling in). We did this with our children when they were young. It is sort of a nice component to an “apartment farm”.

    Connie wrote on April 21st, 2014
  21. I’ve also seen sweet potatoes that have a dark brownish outside and a purple inside? What are those? Thank you

    apartment2504 wrote on October 25th, 2014
  22. i would like to know why japanese sweet potato is much sweeter than ordinary sweet potato. besides it has some sort of sugar liquid after cooking it, is that natural sugar content or there are rumours which state that the farmers grow them by watering with sugar water ? thank you

    at wrote on October 30th, 2014
  23. I actually find the pale sweet potato tastier and sweeter in a nice way than the orange-flesh ones so when I’m cooking just for myself I’m reluctant to turn on the oven just for a small amount of food. I scrub the skins under running water and then steam them whole on the stovetop until they are quite tender. I find that I prefer to eat them plain b/c even butter or cinnamon, to me, interferes with the incredible natural flavor of the potato itself. So I just wait for them to cool enough and cut them into sections and boy oh boy are they great! I’m on the thin side so I don’t worry about calories, plus I find that I always feel so good after eating them, as long as I don’t binge, which I could easily be tempted to do! From your description of the Okinawan Purple I am in search of it… NOW! Thanks also, Mark, for clearing up the differences among the different types.

    Vanessa wrote on December 13th, 2014
  24. Should one eat sweet potatoes raw or always cooked?

    Tyrker wrote on March 12th, 2015
  25. My nutrition professor told me that yams and sweet potatoes aren’t considered a starch because of their red/orange color. I’m so glad to be getting a quality education.

    Aaron Raines wrote on March 17th, 2015
  26. I start everyday with my version of Marks Big Ass Salad. In a skillet, a grill up some grated sweet potato (type varied based on availability) using some olive, hemp and walnut oil, occasionally some ghee. Then 2-4 eggs over mediumish. Add that on top of the salad. Salad consists of every and the kitchen sink, raw. Kale, chard, collard greens, fennel, beets and their shoots, mushrooms (oyster, crimini, domestic), radishes and their leaves, misc carrots, red or yellow onion, red cabbage, celery, diced tumeric and/or ginger, diced apple or other fruits, handful of nuts and seeds (sunflower, pumpkin, hazel, almonds, Brazil, etc), apple cider vinegar, unheated oils, pink Himalayan salt, kelp granules for iodine, fresh squeezed lemon or lime juice, minced or chopped garlic and I carry it around in a big ass bowl to serve as my breakfast and lunch. My bowl is custom, handmaded pottery with the label “chow”. The sweet potato makes the whole meal what it is. Its a must! Oh, and not all ingredients r used every time as it just depends on what I have and I only shop at our local co op so almost all is local and organic.

    Kelsey Kirkpatrick wrote on April 8th, 2015
  27. Something to think about. If you have any room in your yard, and you like gardening at all, grow your own! They’re very easy to grow. Very forgiving, like other tubers. Purchase the ones you like, let the eyes sprout, and then plant them and wait for a tasty reward.

    Chris wrote on May 1st, 2015
  28. In the Philippines sweet potato leaves are generally cooked in most beef stew dishes the leaves impart a very interesting flavor

    Anthony delarosa wrote on February 26th, 2016
  29. Awesome Post! I am a big sweet potato lover as I noticed it helped me with my Adrenal Fatigue considerabely. For a long time I have been eating, or atleast I thought I was, the purple sweet potato but I have become confused if it isn’t actually a yam instead.

    One the box it says it are sweet potatoes grown in America/South America (somtimes africa or Asia) but from the outside they look quite different from the Okinawan version. Maybe you could help me identify what they are exactly!

    They look like this:

    ps. sadly It is nigh impossible to actually buy Okinawan or Japanese sweet potatoes in Holland. Can you buy them instore in the USA ?

    Remon wrote on June 8th, 2016

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