Satsumaimo: The Japanese Sweet Potato

by Joost Nusselder | Updated:  August 26, 2022

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You just can’t miss satsumaimo when its bold red and purple color stares you down. It’s a Japanese sweet potato that you might have seen in the market. A common delicacy at every thanksgiving dinner is Satsuma-Imo—a Japanese sweet potato, which is a favorite of paleo diet enthusiasts.

The sweet potato (Ipomoea batatas) is a dicotyledonous plant that belongs to the family Convolvulaceae.

Its large, starchy, sweet-tasting, tuberous roots are a root vegetable. The young leaves and shoots are sometimes eaten as greens.

Satsumaimo Japanese Sweet Potato

Of the approximately 50 genera and more than 1,000 species of Convolvulaceae, I. batatas is the only crop plant of major importance—some others are used locally, but many are actually poisonous.

This sweet and yellow-fleshed sweet potato strain was traditionally grown in Okinawa and Japan, but you can now find it at any grocery store in America.

This Japanese sweet potato is the staple food of the people from the Okinawa region, and they are some of the most longest-living and healthiest people in the world.

This strain of Japanese sweet potato is sweeter, purple or red-skinned, and yellow-fleshes, full of minerals, antioxidants, and vitamins. In this post, we shall highlight the health benefits, nutritional facts, and a few recipes you can prepare with this potato.

But what really distinguishes it from the American sweet potato is what lies under the sparkling white cover. As one of the earliest plants ever found, it was thought that the sweet potato had its origins around 5,000 years ago in Central America or South America.

The tuber was exported to China sometime later in the 16th century before it reached Japan.

Better grown in milder climates, the crop rose in the southern parts of Japan, with Kyushu having more than 80% of the national production.

Distinguishing satsumaimo from its American equivalent doesn’t take much: where the American sweet potato has brown skin and orange flesh, satsumaimo stands out with a bright reddish-purple skin that encases pale yellow flesh.

Satsumaimo is sweeter, much denser and less oily in terms of taste and appearance and locals have often compared it to a chestnut.

Although the explanation above is that of a common satsumaimo, more than a hundred species of satsumaimo are currently available on the market.

Each type consists of certain characteristics, which are ideal for different cooking techniques, differing in shapes, colors, and tastes.

Murasaki imo (purple sweet potato) is a common variety, a fairly new satsumaimo species with rich purple flesh that is often used in desserts.

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Potato God of Edo

In the Kanto area (including Tokyo) there are several Buddhist temples and Shinto shrines devoted to serving the satsumaimo. Looking through its history, it’s not surprising why.

In the mid-18th century, after years of rice crop failure, Japan and especially the north of Edo (modern-day Tokyo) in the Kanto region, was ravaged by famine. Riots were also common due to widespread famine.

Aoki Konyo found the solution to a lot of these problems when he started cultivating and experimenting with sweet potato and created the satsumaimo.

Shortly after, satsumaimo crops started to thrive and the tuber became an important source of energy to compensate for the lack of rice–a monumental change that saved countless lives.

For this occasion, of his groundbreaking work, Aoki was “Potato God of Edo”.

It Doesn’t Get Any Sweeter Than This

The sweetness and earthy scent of sweet potatoes make them delicious, just steamed, with no additional flavors. Yet satsumaimo is filled with nutrients, like vitamin C, which is an added plus to its great taste.

Vitamin C is a strong antioxidant that helps to improve your immune system, protect your skin from free radical damage (after exposure to the sun) and prevent heart disease.

For those who control their weight, satsumaimo makes an excellent choice of food for several reasons: it is a great source of dietary fiber, known not only to boost bowel movements but also to help you feel full for longer; and due to its high water content of over 60%, each serving size (100 grams) contains only about 130 calories.

Satsumaimo is also recommended for diabetics due to its low glycemic index, which ensures that glucose is released slowly and steadily into the bloodstream.

Certain nutritional benefits of satsumaimo include monitoring your iron levels and blood pressure, improving your metabolism, and supporting the protection of your skin.

Japanese Sweet Potatoes: Nutritional facts & health benefits

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How do you identify sweet potatoes?

When at the grocery store, go to the produce section, where you will find various tubers in a wide variety of colors.

However, you will have a challenge in identifying whether you will be getting a yam, sweet potato, or white potato. These three tubers come from different botanical families, and that’s the reason why many people tend to confuse them.

So, what should you specifically look at?

Different types of sweet potatoes

  • Red or orange skin and orange flesh (mostly mislabeled as yams)
  • Purple skin, with butter-colored flesh (Japanese sweet potatoes)
  • Tan or grey skin, with purple flesh (Okinawan sweet potatoes0
  • Pale yellow skin, with butter-colored flesh
  • Purple skin with purple flesh

When it comes to the taste, orange sweet potatoes tend to be sweeter and softer, while the other varieties are starchier and drier. Most of the grocery stores sell orange potatoes, even though you will find other varieties at Asian markets.

Also read: different kinds of popular Japanese food

Varieties of white potatoes

  • Brown of beige skin, with white flesh (these are the typical russet potatoes)
  • Blue or purple skin, with white flesh

It’s also important to note that there are different varieties of Japanese sweet potatoes, but the common ones include:

  • Beni Azima – this variety is mostly eaten in Eastern Japan, and it turns very sweet when cooked
  • Naruto Kintoki – very common in Western Japan, and it’s considered to be sweet and elegant
  • Tosabeni – given a No. 14 value (top) attribution, and it’s a brand name sweet potato
  • Manasume – this is another No. 14 value sweet potato brand
  • Gorou Shima Kintoki – mostly common as bakes sweet potato
  • Kougane Segan – categorized as the popular Sochu sweet potato
  • Tanegashima Mukashi Mistu-Imo – this is a sweet potato variety with an elegant taste, as well as a beautiful orange color
  • Tanegashima Murasaki Imo – has a very elegant purple color
  • Annou Imo – its rich in carotenes, and comes in a beautiful orange color, with a very sweet taste
  • Tanegashima Gold Imo – this sweet potato variety is grown in Taneko Island, located in the south of Kyushu, and it’s usually red when raw, and then changes to deep golden color when cooked. Amongst all these different varieties of Japanese sweet potatoes, the violet sweet potatoes are becoming more common.

Japanese sweet potatoes nutritional facts

The phytonutrients linked to different colors of sweet potatoes have unique health properties. However, all the sweet potato strains come with a similar nutritional profile.

They are rich in minerals, vitamins, and phytonutrients, and that’s the reason they are considered to be the healthiest amongst all other vegetables.

Even though many people rarely consume sweet potato leaves, they are a very good source of minerals, protein, and fiber. The micronutrient, macronutrient, and phytonutrient information we have given below are for the sweet potato tuber.

  • Carbohydrates – in every 100 g (86 calorie) sweet potato serving, you get 20.1 g carbohydrates. Out this, 3.0 g is fiber, 4.2 g are sugars (glucose, sucrose, maltose, and fructose), and 12.7 g is starch. Sweet potato starch contains high levels of amylose than amylopectin, which raises blood sugar gradually. As a result, sweet potato is one of the best food choices for diabetics.
  • Protein – although sweet potatoes mainly a source of healthy fiber and starch, they also have 1.6 g of protein per 100 g serving.
  • Fats – sweet potatoes have a very low-fat content, which is just 0.1 g per 100 g serving, and they do not contain any saturated fats.
  • Vitamins – it’s important to note that Japanese sweet potatoes are very rich in vitamins, particularly beta-carotene (provitamin A), vitamins B5, and B6.
  • Minerals – also, Japanese sweet potatoes are low in sodium and a good source of some minerals.
  • Phytonutrients – sweet potatoes contain various beneficial phytonutrient. Although some phytonutrients can be found in all sweet potato strains, others do vary, depending on the color of the flesh. The Japanese sweet potato is mainly rich in coumarins, quercetin, peonidin, chyrsoeriol, and kaempferol.
  • Phytosterols – these are cholesterol-like molecules found in plant cells. Research has revealed that eating 2 g of phytosterols each day can lower low-density lipoprotein by 10%. The most common phytosterol that’s found in Japanese sweet potato is β-Sitosterol. Campesterol is the second most common, and aliphatic as well as α-tocopherol are also found in smaller quantities.
  • Polyphenols – these work as antioxidants in our bodies. They assist in preventing cancer, Parkinson’s diseases, heart disease, as well as other neurodegenerative disorders. The Japanese strain of sweet potato is full of phenolic acids, and they are also rich in coumarins. Moreover, yellow-fleshed sweet potatoes also contain high quantities of flavonoids (chyseoriol, kaempferol, peonidin, and quercetin).

Health benefits of Japanese sweet potatoes

sweet potatoes

Other than being delicious and nutritious, Japanese sweet potatoes come packed with several health benefits. Here are some of the benefits:

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A natural antioxidant

When free radicals react with other molecules in your body, they can cause damage, thus promoting disease. But, Japanese sweet potatoes are full of antioxidants, and this includes vitamins A and E. in addition to that they are also full of antioxidant phytonutrients, like flavonoids and polyphenols.

Moreover, Japanese sweet potatoes also contain some novel antioxidants. Metallothioneins (which are proteins), as well as other polyphenols (derivatives of caffeoylquinic acid) found in Japanese sweet potatoes, are also powerful antioxidants.

Furthermore, sweet potato leaves contain high levels of antioxidants, particularly polyphenols. Baking and boiling sweet potatoes are known to boost their antioxidant activity.

They help in preventing heart disease

In a study, diabetic mice were given 150 gm/kg of body weight flavonoids that were extracted from the leaves of sweet potatoes—and this reduced triglycerides and cholesterol.

When the researches fed the mice a diet of high-fat sweet potatoes for 4 months, their arteries hardened less compared to mice who were given a high-fat diet without sweet potatoes. This is an indication that sweet potatoes can assist in preventing hardened arteries that are caused by high-fat diets.

Prevents constipation

Japanese sweet potato can improve your digestion, thus preventing constipation. In a study where 120 leukemia patients who were undergoing chemotherapy were given 200 g or sweet potato each, they had fewer cases of constipation, as well as improved bowel movements.

In another research, a group of 93 patients with the acute coronary syndrome (a heart disease) was given a treatment regimen consisting of sweet potatoes, acupressure massage, and foot baths, and they showed reduced constipation. The patients also used a few enemas and laxatives, and they were comfortable with their bowel movements.

Assists in the prevention of cancer

A research conducted on human cells revealed that polyphenols, which is extracted from Japanese sweet potato leaves could suppress the growth of cancer cells. Also, some researchers argue that phytonutrients can assist in the prevention of cancer. Besides, there is another molecule (IbACP, or Ipomoea Batatas anti-cancer peptide), which researchers have revealed that it killed pancreatic cancer cells.

Boosts immunity

Japanese sweet potatoes are full of antioxidants that inhibit free radical damage in our bodies. When you take a cup of baked sweet potato, you get close to 52% of the daily value of vitamin C—and this is important for tissue repair and wound healing.

Also, Japanese sweet potatoes contain vitamin A, which assists your body to produce immune cells that deny the growth of disease and infections and also has some anti-tumor effects.

Improves your eyesight

Satsuma-Imo has a number of nutrients that are linked to improved vision as well as eye health. Some of the most powerful nutrients are the carotenoids, and they include lutein, zeaxanthin, alpha-carotene, and beta-carotene.

When you take beta-carotene when isolated from other carotenoids, it can cause some imbalances. However, when it takes in foods, where it’s accompanied by other carotenoids, it has very powerful anti-cancer and vision-boosting properties.

Sweet potatoes can improve fertility

Sweet potatoes are a fantastic source for vitamin A, which is an essential nutrient for reproduction health. In addition, they also contain a rich supply of iron, which is known to support fertility.

Assists in stabilizing blood sugar

Japanese sweet potatoes have complex carbohydrates and fiber, which plays an important role in stabilizing your blood sugar, and it can also assist you to feel full for an extended period of time.

Bottom Line

There you go! This all what you need to know to make an informed decision about consuming Japanese sweet potatoes—and we promise you that you won’t be regret it any bit. You just need to try it out and experience the benefits first hand.

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Joost Nusselder, the founder of Bite My Bun is a content marketer, dad and loves trying out new food with Japanese food at the heart of his passion, and together with his team he's been creating in-depth blog articles since 2016 to help loyal readers with recipes and cooking tips.