What’s the Difference Between Sweet Potatoes and Yams?

Dieser Artikel basiert auf wissenschaftlichen Studien

Sweet Potatoes | Yams | Same Thing | Difference | Conclusion | FAQ | Studies

Paleo and low-carb enthusiasts reach for it when they want to replenish their glycogen stores. Hence, sweet potato is a healthy source of carbohydrates after intense workouts or carb cycling.

However, it is often confused with a similar root – yams.

Although yams and sweet potatoes share some similarities in their uses, there is a distinct difference.

Find out how to identify the difference between yams and sweet potatoes and which tuber fits which purposes.

What’s the Difference Between Sweet Potatoes and Yams?

Most of us have never eaten a real yam. However, many of us have bought yams that turned out to be sweet potatoes.

Why?

The reason for the confusion is marketing.

When orange-fleshed sweet potatoes were introduced to the United States in the mid-20th century, they were called yams to avoid confusion with the original white-fleshed sweet potato that was first on the market.

When we look at sweet potatoes and yams in detail, it becomes clear that there’s a difference between the two plants.

What Are Sweet Potatoes?

The sweet potato or Ipomoea batatas belong to the bindweed or morning glory family – Convolvulaceae.

Therefore, strictly speaking, the sweet potato is not a potato. Contrary to popular belief, it also does not belong to the botanical nightshade family like the potato.

Nevertheless, both families are widely related to each other, as they belong to the order Solanaceae.

Moreover, the sweet potato is native to South America, domesticated at least 5000 years ago.

The root vegetable typically has brown or reddish skin with a starchy interior that is orange. However, varieties exist whose interiors can be white or purple.

White Sweet Potatoes

Although the orange sweet potato is more common, the one that has a white interior is the classic sweet potato.

In short, you’ll recognize the white sweet potato by its light brown skin and slightly yellow interior. It is only slightly sweet but still has a creamy texture.

Orange Sweet Potatoes

Orange on its inside and reddish-brownish-orange on its outside – this is the sweet potato as we know it.

Since this sweet potato is colloquially known as “yams” in the USA, many confusions arise. For this reason, yams are also usually mistranslated into sweet potatoes in many dictionaries.

Furthermore, they are sweeter than the classic white sweet potatoes and are now available on almost every corner in the western world.

Purple Okinawa Sweet Potato

Now we come to the Asian market. While their exterior tends to be white, you can identify Okinawa sweet potatoes with a bright purple inside.

Like blackberries, for example, they get their purple color from anthocyanins. These are color pigments that are said to have an antioxidant effect.

According to studies, purple sweet potatoes have more powerful and, above all, more stable anthocyanins than berries (Li et al. 20191).

Although they have as creamy a texture as orange sweet potatoes, they are even sweeter than this relative.

Japanese Satsumaimo Sweet Potato

The satsumaimo is also called Japanese sweet potato. Its characteristics are precisely opposite to the purple sweet potato: while the skin is purple, the inside is yellow.

Moreover, what sets this sweet potato apart is its tremendous sweetness. When you caramelize satsumaimo in the oven, it tastes remarkably sweet. At the same time, the inside becomes especially golden when you bake it.

Therefore, many people use them in desserts.

What Are Yams?

Unlike the sweet potato, yams or Dioscorea belong to the yam family or Dioscoreaceae, mainly distributed in the tropics.

Therefore, they are more closely related to lilies and grasses, for example. Their skin is rougher and more bark-like than that of a sweet potato. Also, yams are usually white or yellowish rather than orange on their inside.

Yam was derived from either the Spanish “name” or the Portuguese “inhame.”

However, both words derive from the African Wolof word “nyam,” which means taste.

Another African language uses “yamyam” for chew, which highlights the importance of yam in the local diet.

Consequently, the root is a popular ingredient in Africa, the Caribbean, and also Asia. In some cases, it’s even a staple food, such as potatoes are to us.

Therefore, yams are usually sold only in international grocery stores, while you can get sweet potatoes in the supermarket.

Because the inside of yam is less moist, they require more fat to be prepared to a similar softness and creaminess as sweet potatoes.

They are also less sweet than their orange counterparts. Nonetheless, yams exist in just as much variety.

African White or Yellow Yam

The African one is the original yam, of which there are over 200 varieties. Traditional preparation takes many forms, but the most common method is to peel and boil or process into a puree.

Although we can only see the white yam in select stores, you can find it in many places in Africa as a staple food.

Also, the flesh of the classic variety is white to yellowish.

Purple Water Yam

The purple yam was initially cultivated in Southeast Asia and is now the most widespread variety. Thus, it probably represents the counterpart of the Okinawa sweet potato.

Although it is grown in Africa, Asia, the Pacific Islands, and the Caribbean, it has also crept into the southern United States.

While their purple interior can identify water yams, their skin is also purple to brownish.

Chinese Yam

Like water yams, Chinese yams have also made their way to the West. It was initially cultivated in China, Japan, and Korea.

After being pickled in a vinegar solution to render the oxalates in the peel harmless, it is the only yam species that can be eaten raw.

Similar to the African variety, Chinese yam is white to the yellowish inside. Unlike the conventional tuber, however, its skin is golden yellow.

Sweet Potatoes vs. Yams – Same Things

Since sweet potatoes and yams have a similar texture, you can prepare both tubers in many ways. For example, they can be boiled, baked, steamed, roasted, or fried.

Moreover, both roots are considered healthy for the intestinal flora, not only for allergics but in general.

One reason for this is the lack of a form of plant toxins that are particularly hard on the intestines.

Lectin-Free

The fact that both yams and sweet potatoes do not belong to the nightshade or cucurbit family gives the tubers a common advantage.

Therefore, both are low in lectins.

Lectins are sticky proteins that plants use to protect themselves against predators. Although there are many different types of them, most people are only familiar with gluten.

While lectins can paralyze parasites, the effects on the human body are not as quickly noticeable. However, studies show that these plant toxins cause us long-term harm.

Thus, some of the most significant hazards of lectins to human health are (Haupt-Jorgensen et al. 20182; Dalla Pellegrina et al. 20093; (Kamikubo et al. 20084):

  • Damage to the intestinal wall or leaky gut
  • Transport of pathogens from the intestine to the blood and organs
  • Promotion of insulin resistance and weight gain

And this is where the wheat is literally separated from the chaff, although that’s precisely the place where aggressive lectins are hidden (Shechter 19835).

For this reason, whole grains are neither great for weight loss nor your gut.

Against this background, it becomes clear that most carbohydrate sources in our Western diet are full of lectins.

But both sweet potatoes and yams show a difference here. Therefore, both tubers are considered healthy sources of carbohydrates.

For this reason and the lower carbohydrate content, the sweet potato is superior to the conventional potato, even though the latter contains more resistant starches.

Resistant Starches

Furthermore, where sweet potato and yams do not show a difference is in the type of carbohydrates they have stored.

As the fat pad in humans, starch in tubers is a long-term energy store formed in conjunction with photosynthesis.

Chemically, starches represent complex sugars or polysaccharides.

While conventional starches, such as those found in bread, pasta, cakes, or cereals, are quickly digested by the body, resistant starches are not (Birt et al. 20136).

As the name suggests, resistant starch is resistant in a certain sense – to digestion.

Because these carbohydrates are resistant to breakdown by enzymes in the small intestine, they are considered prebiotics that may cause health benefits.

Accordingly, resistant starch is fermented by microbes in the large intestine into short-chain fatty acids, gases, and other products that can affect human health.

In this process, the amount and type of carbohydrates that enter the colon influence the microbiome’s composition (Maier et al. 20177).

Although research on resistant starch is not yet mature, it is said to have the following health benefits:

  • Smaller blood glucose and insulin response
  • Decreased triglyceride levels
  • Improved insulin sensitivity
  • Increased satiety
  • Decreased fat storage

The researchers suggest that the conversion to short-chain fatty acids is responsible for potential health benefits (Higgins 20048).

With this in mind, yams are the supposedly better choice because they contain more resistant starches than sweet and conventional potatoes (Birt et al. 20139).

Yams and Sweet Potatoes – the Difference

So, the first profound difference between sweet potatoes and yams is that they come from different botanical families.

Also, differences exist in the preparation of the two elongated roots.

Since sweet potatoes are available in most supermarkets, they found their way into several dishes that have become established in our Western cuisine.

Above all, people prepare sweet potato fries with them, a popular alternative to baked or mashed potatoes.

sweet potatoes are used for fries - a difference to yams

Moreover, in the USA, the tuber has established itself as a sweet potato pie or sweet potato casserole for thanksgiving. Nevertheless, you usually bake, mash, roast, or use them in soups.

In contrast, you will hardly find real yams in Western supermarkets. However, due to its long shelf life, it is a staple food in Africa.

There, the roots are usually boiled, roasted, or fried. Moreover, people widely use yams in Africa as powder or flour. In this form, it is either made into a kind of bread substitute or a puree.

However, in our country, you will only find yam flour in delicatessens that specialize in African products.

We can also see that they are not the same tuber when we compare the nutrition facts.

Nutrients

While sweet potatoes do not contain much fat or protein, they are over ¾ water.

Sweet potatoes’ preparation makes a difference. Unlike raw tubers (*), baked sweet potatoes may contain more vitamin C.

Accordingly, 100 grams of sweet potatoes baked in their skins provide following nutrient facts (*):

  • Calories: 90
  • Carbohydrates: 20.7 g
  • Dietary fiber: 3.3 g
  • Net carbohydrates: 17.4 g
  • Vitamin A: 384%
  • Vitamin C: 33%
  • Pyridoxine (B6): 14%
  • Potassium: 14%
  • Manganese: 25%

In comparison, 100 grams of baked yams (*) provide:

  • Calories: 116
  • Carbohydrates: 27.5 g
  • Dietary fiber: 3.9 g
  • Net carbohydrates: 23.6 g
  • Vitamin A: 2%
  • Vitamin C: 20%
  • B6 (pyridoxine): 11%
  • Potassium: 19%
  • Manganese: 19%

In the comparison, both roots score high in same micronutrients but to different extents.

Vitamins and minerals, which neither yams nor sweet potatoes can provide 10% of daily requirements, were intentionally not listed above.

There is a significant difference between sweet potatoes and yams in vitamin A content. While baked yams can meet only 2% of the daily requirement, sweet potatoes impress with 384%.

However, this nutrient claim has a catch. It is not highly bioavailable retinol (vitamin A1) but provitamin A (beta-carotene).

Suppose one considers that according to a study, the body absorbs less than 2.25% and converts less than 0.03% of beta-carotene into vitamin A (Hickenbottom et al. 200210).

Thus, the supposed 384% of the daily requirement becomes a negligible 0.11%.

For example, those who want to strengthen eyesight and immune function with vitamin A may instead eat liver since only animal products can provide retinol (Sommer 201411).

Nevertheless, both roots provide vitamin C, B6, potassium, and manganese, which may improve the following functions (Holley et al. 201112; Parra et al. 201813; Zhu et al. 200914):

  • Immune system
  • Metabolism
  • Bone density

Carbohydrates and Blood Sugar

In terms of calories and net carbohydrates, sweet potatoes perform slightly better than yams. However, it would be best to use both tubers for carb cycling rather than a keto diet.

Regarding blood sugar, it is also better to boil both roots rather than bake or fry them.

While 100 grams of boiled sweet potatoes cause the same blood sugar increase as 11 grams of glucose (*), baked ones would generate the equivalent of 42 grams of glucose (*).

This glycemic load is 13 (*) for cooked yams and about 28 (*) for roasted ones.

Accordingly, the difference between sweet potatoes and yams is only partially significant for people with diabetes or low-carb advocates.

Health benefits

The orange interior of the sweet potato indicates its health potential, since they contain carotenoids.

On the one hand, the beta-carotene may boost vitamin A production, although this effect is often manageable (Lin et al. 200015).

On the other hand, the carotenoids combined with antioxidants in sweet potato exert an effect that could reduce cancer and cardiovascular disease (Hou 200316).

In this regard, purple Okinawa sweet potato is considered the tuber with the highest antioxidants content (Li et al. 201917).

Moreover, studies suggest that sweet potatoes may improve glucose and lipid metabolism in people with insulin resistance and type 2 diabetes (Ludvik et al. 200818; Kusano et al. 200019).

There is a subtle but significant difference between sweet potatoes and yams

Unlike sweet potatoes, the health effects of yams have not been studied to the same extent. Nonetheless, studies do exist, particularly looking at the impact on post-menopausal women.

Researchers concluded that yam’s health benefits could reduce cancer and cardiovascular disease (Wu et al. 200520).

Moreover, another study dealt with the effect of yam extract on unpleasant symptoms of menopause.

Thereby, yam extract could alleviate the symptoms to a manageable extent but did not cause any side effects (Komesaroff et al. 200121).

For this reason, yams could represent a natural alternative to hormone therapy.

According to recent studies, Chinese yam extract, in particular, can produce estrogen-like effects that could play a further role in this regard (Zeng et al. 201822).

However, yam also seems to affect memory function, according to a Japanese study that administered yam extract with olive oil to volunteers aged 20 to 81.

While it did not cause side effects, the yam extract successfully improved the participants’ cognitive thinking ability (Tohda et al. 201723).

Sweet Potatoes and Yams Are Not the Same Thing

Although they are sometimes both touted as yams, sweet potatoes and yams are different plants.

However, the bottom line is that both are healthier sources of carbohydrates than those established in Western diets.

For this reason, sweet potatoes are considered a food you can eat after an intense workout when you want to replenish your glycogen stores.

However, despite its narrower notoriety, yam can also be a similarly good option.

On the one hand, its high content of resistant starch makes yams healthier food for gut bacteria. But on the other hand, they contain more net carbohydrates than sweet potatoes.

Since the sweet potato’s supposed vitamin A advantage relies only on minimally convertible beta-carotene, the tubers balance each other out overall.

Accordingly, you can add variety to your plate with yams, provided you can get hold of them in organic or health food stores.

Difference Between Sweet Potatoes and Yams FAQ

Which is healthier sweet potato or yam?

While sweet potatoes have a slightly better nutritional profile, yams contain more resistant starch. In short, both tubers are about equally healthy.

Why do we call sweet potatoes yams?

The confusion is based on the name given to orange sweet potatoes as yams when they were first introduced to the U.S. market. The different name was intended to clearly distinguish it from the traditional white sweet potato.

Can you substitute yams for sweet potatoes?

You can substitute yams for sweet potatoes because they have a similar texture. African yams are just not quite as creamy, which is why they require more fat, for example, as a puree.

Studies

#1-7

1 Li A, Xiao R, He S, An X, He Y, Wang C, Yin S, Wang B, Shi X, He J. Research Advances of Purple Sweet Potato Anthocyanins: Extraction, Identification, Stability, Bioactivity, Application, and Biotransformation. Molecules. 2019 Oct 23;24(21):3816. doi: 10.3390/molecules24213816. PMID: 31652733; PMCID: PMC6864833.

2 Haupt-Jorgensen M, Holm LJ, Josefsen K, Buschard K. Possible Prevention of Diabetes with a Gluten-Free Diet. Nutrients. 2018 Nov 13;10(11):1746. doi: 10.3390/nu10111746. PMID: 30428550; PMCID: PMC6266002.

3 Dalla Pellegrina C, Perbellini O, Scupoli MT, Tomelleri C, Zanetti C, Zoccatelli G, Fusi M, Peruffo A, Rizzi C, Chignola R. Effects of wheat germ agglutinin on human gastrointestinal epithelium: insights from an experimental model of immune/epithelial cell interaction. Toxicol Appl Pharmacol. 2009 Jun 1;237(2):146-53. doi: 10.1016/j.taap.2009.03.012. Epub 2009 Mar 28. PMID: 19332085.

4 Kamikubo Y, Dellas C, Loskutoff DJ, Quigley JP, Ruggeri ZM. Contribution of leptin receptor N-linked glycans to leptin binding. Biochem J. 2008 Mar 15;410(3):595-604. doi: 10.1042/BJ20071137. PMID: 17983356.

5 Shechter Y. Bound lectins that mimic insulin produce persistent insulin-like activities. Endocrinology. 1983 Dec;113(6):1921-6. doi: 10.1210/endo-113-6-1921. PMID: 6357762.

6 Birt DF, Boylston T, Hendrich S, Jane JL, Hollis J, Li L, McClelland J, Moore S, Phillips GJ, Rowling M, Schalinske K, Scott MP, Whitley EM. Resistant starch: promise for improving human health. Adv Nutr. 2013 Nov 6;4(6):587-601. doi: 10.3945/an.113.004325. PMID: 24228189; PMCID: PMC3823506.

7 Maier TV, Lucio M, Lee LH, VerBerkmoes NC, Brislawn CJ, Bernhardt J, Lamendella R, McDermott JE, Bergeron N, Heinzmann SS, Morton JT, González A, Ackermann G, Knight R, Riedel K, Krauss RM, Schmitt-Kopplin P, Jansson JK. Impact of Dietary Resistant Starch on the Human Gut Microbiome, Metaproteome, and Metabolome. mBio. 2017 Oct 17;8(5):e01343-17. doi: 10.1128/mBio.01343-17. PMID: 29042495; PMCID: PMC5646248.

#8-13

8 Higgins JA. Resistant starch: metabolic effects and potential health benefits. J AOAC Int. 2004 May-Jun;87(3):761-8. PMID: 15287677.

9 Birt DF, Boylston T, Hendrich S, Jane JL, Hollis J, Li L, McClelland J, Moore S, Phillips GJ, Rowling M, Schalinske K, Scott MP, Whitley EM. Resistant starch: promise for improving human health. Adv Nutr. 2013 Nov 6;4(6):587-601. doi: 10.3945/an.113.004325. PMID: 24228189; PMCID: PMC3823506.

10 Hickenbottom SJ, Follett JR, Lin Y, Dueker SR, Burri BJ, Neidlinger TR, Clifford AJ. Variability in conversion of beta-carotene to vitamin A in men as measured by using a double-tracer study design. Am J Clin Nutr. 2002 May;75(5):900-7. doi: 10.1093/ajcn/75.5.900. PMID: 11976165.

11 Sommer A. Preventing blindness and saving lives: the centenary of vitamin A. JAMA Ophthalmol. 2014 Jan;132(1):115-7. doi: 10.1001/jamaophthalmol.2013.5309. PMID: 24407830.

12 Holley AK, Bakthavatchalu V, Velez-Roman JM, St Clair DK. Manganese superoxide dismutase: guardian of the powerhouse. Int J Mol Sci. 2011;12(10):7114-62. doi: 10.3390/ijms12107114. Epub 2011 Oct 21. PMID: 22072939; PMCID: PMC3211030.

13 Parra M, Stahl S, Hellmann H. Vitamin B₆ and Its Role in Cell Metabolism and Physiology. Cells. 2018 Jul 22;7(7):84. doi: 10.3390/cells7070084. PMID: 30037155; PMCID: PMC6071262.

#14-21

14 Zhu K, Devine A, Prince RL. The effects of high potassium consumption on bone mineral density in a prospective cohort study of elderly postmenopausal women. Osteoporos Int. 2009 Feb;20(2):335-40. doi: 10.1007/s00198-008-0666-3. Epub 2008 Jun 25. PMID: 18575949.

15 Lin Y, Dueker SR, Burri BJ, Neidlinger TR, Clifford AJ. Variability of the conversion of beta-carotene to vitamin A in women measured by using a double-tracer study design. Am J Clin Nutr. 2000 Jun;71(6):1545-54. doi: 10.1093/ajcn/71.6.1545. PMID: 10837297.

16 Hou DX. Potential mechanisms of cancer chemoprevention by anthocyanins. Curr Mol Med. 2003 Mar;3(2):149-59. doi: 10.2174/1566524033361555. PMID: 12630561.

17 Li A, Xiao R, He S, An X, He Y, Wang C, Yin S, Wang B, Shi X, He J. Research Advances of Purple Sweet Potato Anthocyanins: Extraction, Identification, Stability, Bioactivity, Application, and Biotransformation. Molecules. 2019 Oct 23;24(21):3816. doi: 10.3390/molecules24213816. PMID: 31652733; PMCID: PMC6864833.

18 Ludvik B, Hanefeld M, Pacini G. Improved metabolic control by Ipomoea batatas (Caiapo) is associated with increased adiponectin and decreased fibrinogen levels in type 2 diabetic subjects. Diabetes Obes Metab. 2008 Jul;10(7):586-92. doi: 10.1111/j.1463-1326.2007.00752.x. Epub 2007 Jul 21. PMID: 17645559.

19 Kusano S, Abe H. Antidiabetic activity of white skinned sweet potato (Ipomoea batatas L.) in obese Zucker fatty rats. Biol Pharm Bull. 2000 Jan;23(1):23-6. doi: 10.1248/bpb.23.23. PMID: 10706405.

20 Wu WH, Liu LY, Chung CJ, Jou HJ, Wang TA. Estrogenic effect of yam ingestion in healthy postmenopausal women. J Am Coll Nutr. 2005 Aug;24(4):235-43. doi: 10.1080/07315724.2005.10719470. PMID: 16093400.

21 Komesaroff PA, Black CV, Cable V, Sudhir K. Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women. Climacteric. 2001 Jun;4(2):144-50. PMID: 11428178.

#22-23

22 Zeng M, Zhang L, Li M, Zhang B, Zhou N, Ke Y, Feng W, Zheng X. Estrogenic Effects of the Extracts from the Chinese Yam (Dioscorea opposite Thunb.) and Its Effective Compounds in Vitro and in Vivo. Molecules. 2018 Jan 23;23(2):11. doi: 10.3390/molecules23020011. PMID: 29360751; PMCID: PMC6017084.

23 Tohda C, Yang X, Matsui M, Inada Y, Kadomoto E, Nakada S, Watari H, Shibahara N. Diosgenin-Rich Yam Extract Enhances Cognitive Function: A Placebo-Controlled, Randomized, Double-Blind, Crossover Study of Healthy Adults. Nutrients. 2017 Oct 24;9(10):1160. doi: 10.3390/nu9101160. PMID: 29064406; PMCID: PMC5691776.

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