Common at Thanksgiving dinner and a darling of paleo diet enthusiasts, orange-fleshed sweet potatoes are just one of more than 400 strains grown around the world. Satsuma-imo, Japanese sweet potato, is a sweeter, red or purple skinned, yellow-fleshed option packed with vitamins, minerals, and antioxidants. Keep reading to learn more about the health benefits, side effects and reviews of the Japanese Sweet Potato.
What are Sweet Potatoes?
Sweet potatoes, or Ipomoea batatas, originated in Central or South America and have been cultivated by humans for over 5000 years. Today, there are over 400 strains of sweet potato grown around the world. Different parts of the plant, such as the leaves, stems and root tubers, are used for food, medicine and animal feed [R].
Sweet potatoes are only distantly related to potatoes. Sweet potatoes belong to the same family as morning glory (Convolvulaceae), while potatoes are a nightshade (Solanaceae). Potato tubers are derived from the plant stems while sweet potato tubers are derived from the root [R].
Satsuma-imo, or Japanese sweet potato, is a sweet, yellow-fleshed strain. Traditionally grown in Japan and Okinawa, it is now available at grocery stores across North America. It is a staple food of the Okinawans, who are some of the healthiest and longest-lived people on Earth. Their good health and long lifespan are attributed, in part, to their diet [R, R].
The Japanese sweet potato is distinct from the Okinawan sweet potato, which is purple-fleshed. The Okinawan people eat both in abundance [R].
Components in Japanese Sweet Potato Tubers
The phytonutrients associated with different colors in sweet potato do have different health properties. Besides that, however, sweet potato strains have a very similar nutritional profile. Rich in vitamins, minerals, and phytonutrients, sweet potato has been named the ‘healthiest of all vegetables’ by The Center for Science in the Public Interest [R].
Sweet potato leaves are rarely consumed in western countries but are a good source of fiber, protein, and minerals. The macronutrient, micronutrient, and phytonutrient information provided below are for the tuber, which is the part that’s usually eaten [R, R].
In a 100 g (86 calorie) serving of sweet potato, there are 20.1 g of carbohydrates. Of this, 12.7 g are starch, 4.2 g are sugars (sucrose, glucose, fructose, and maltose) and 3.0 g is fiber. Sweet potato starch is higher in amylose than amylopectin, which raises blood sugar slowly. This makes it a healthy food choice for diabetics [R].
Sweet potatoes are primarily a source of healthy starch and fiber, but they also contain 1.6 g of protein in a 100 g serving [R].
Sweet potatoes are very low in fat, with just 0.1 g in a 100 g serving. There are no saturated fats in sweet potatoes [R].
Sweet potatoes are a good source of many beneficial phytonutrients. While some phytonutrients are found in all sweet potatoes, others vary depending on the flesh-color. The yellow-fleshed satsuma-imo is particularly rich in coumarins, peonidin, quercetin, kaempferol and chrysoeriol [R, R].
Phytosterols are a cholesterol-like molecule found in plant cells. In a meta-analysis of 41 trials, consuming 2 g of phytosterols a day was found to lower low-density lipoprotein or LDL (‘bad’ cholesterol) by 10 % [R].
The most abundant phytosterol found in sweet potato is β-Sitosterol (55.2–77.6% of all phytosterols found). Campesterol was the second most abundant. Aliphatic alcohols and α-tocopherol were also found in smaller amounts [R].
Yellow-fleshed sweet potatoes like the Japanese sweet potato are rich in phenolic acids. They are especially rich in coumarins [R].
Japanese Sweet Potato as Part of the Lectin Avoidance Diet
Japanese sweet potatoes, like all sweet potatoes, are low in harmful lectins (to see a list of other foods low in lectins, click here).
Lectins are proteins that bind to carbohydrates. Although not all lectins are bad, some lectins and other substances found in plants can trigger immune reactions and damage the gut in certain people. These substances can be found in seemingly healthy foods like whole grains, beans, tomatoes, or fruit. Gluten (or gliadin), a protein found in wheat, barley, and rye, is a particularly dangerous type of lectin that can cause a lot of damage in the body [R, R, R, R].
Food sensitivity is a set of inflammatory or adverse reactions to food that isn’t an allergic reaction. While food allergies cause an immediate reaction (such as rashes, hives, pain, swelling, and in extreme cases, asthma/airway closure or anaphylactic shock), food sensitivities are usually not immediate and the inflammatory symptoms can last for a few days. Usually, a food sensitivity will cause symptoms that are obscure and don’t fit neatly into any diagnosis such as brain fog, pain, fatigue, anxiety, and insomnia [R].
Although there are food sensitivity tests available, several studies have shown they are not accurate or effective. The gold standard to identify non-allergic food sensitivities is to eliminate the food and bring it back. People with inflammation issues, autoimmune disease (Th1, Th2, Th17 dominance or leaky gut), histamine intolerance, or unexplainable health issues should experiment with an elimination diet, such as the Lectin Avoidance Diet, to see if their symptoms improve.
This cookbook is a guide to doing an elimination diet, starting with a list of foods that should be low in inflammation (usually doesn’t cause a reaction). After your symptoms subside, you can bring back eliminated food, one at a time, to see their effects. This cookbook allows you to figure out what works to reduce your symptoms, in a sustainable and delicious way.
Health Benefits of Japanese Sweet Potato
In addition to being nutritious and delicious, the Japanese sweet potato has multiple health benefits. Here are 8 studied health benefits of the Japanese sweet potato [R].
1) Japanese Sweet Potato Is An Antioxidant
In addition to these well-known substances, sweet potatoes also have some novel antioxidants. Two proteins (metallothioneins) and four polyphenols (derivatives of caffeoylquinic acid) discovered in sweet potatoes are powerful antioxidants (tissue and cell studies) [R, R].
In an animal study, sweet potato extract reversed brain damage (neurotoxicity) in mice. A follow-up study on mouse brain tissue showed that it worked by functioning as an antioxidant [R].
Baking and boiling sweet potatoes increase their antioxidant activity [R].
2) Sweet Potato Prevents Heart Disease
When mice were fed a high-fat, sweet potato diet for 16 weeks, their arteries hardened less than mice who were fed a high-fat diet without sweet potato. This indicates sweet potatoes might help prevent the hardened arteries caused by high-fat diets [R].
3) Sweet Potato Prevents Constipation
Sweet potato also helps with constipation. In a study (RCT) of 120 leukemia patients undergoing chemotherapy, eating 200 g of sweet potato per day prevented constipation and increased satisfaction with bowel movements [R].
In another study (RCT) of 93 patients with heart disease (acute coronary syndrome), the group that received a treatment including sweet potatoes, foot baths, and acupressure massage had significantly less constipation. They also used fewer laxatives and enemas and were more satisfied with their bowel movements [R].
4) Sweet Potato May Help Prevent Cancer
In a study of human cancer cells, polyphenols (caffeic acid and 3,4,5-tri-O-caffeoylquinic acid) extracted from sweet potato leaves suppressed cancer’s growth. The researchers concluded these phytonutrients may help prevent cancer [R].
Another molecule isolated from sweet potato leaves, (Ipomoea batatas anti-cancer peptide, or IbACP) caused cell death in pancreatic cancer cells [R].
5) Sweet Potatoes May Fight Microbes
A protein (defensin) isolated from sweet potato tubers prevents the growth of fungi and bacteria. This indicates it may be able to fight microbes [R].
6) Sweet Potato May Reduce Inflammation
Sweet potatoes contain oxalic acid, which can combine with calcium in the kidneys to produce kidney stones in people who are susceptible. Many people around the world eat sweet potatoes as a staple food without any ill effects. But if you are on a low oxalate diet, you should talk to your doctor about what amount of sweet potato (if any) is safe to consume [R, R].
Limitations and Caveats
While there is ample research indicating that Japanese sweet potatoes are rich in antioxidants, there is very limited research on other health benefits. With the exception of one animal study that looked at the effect of sweet potatoes on artery hardening, all other research has been on sweet potato extracts. There is no evidence that eating Japanese sweet potatoes will have the same health benefits as concentrated extracts.
Natural Sources and Supplements
Japanese sweet potatoes are available in the produce aisle of most grocery stores.
Many people enjoy the sweet flavor of Japanese sweet potatoes. Their dry, creamy texture makes them perfect for making sweet potato oven fries. Other popular preparations include baking, roasting, and boiling.
Some people prefer orange or purple-fleshed sweet potatoes because they believe they have a better nutritional profile or are lower in sugars, however, the differences are minor.
Japanese Sweet Potato Recipe
If you are interested in trying (or already love) Japanese sweet potatoes, try this delicious low-lectin recipe! Japanese sweet potatoes are flavorful, do not have any lectins, and are rated less inflammatory, which is great for those who have a lectin sensitivity. For a list of other foods low in lectins, click here.
Mashed Japanese Sweet Potatoes
This delicious dish is flexible and serves 4.
- Peel and cut 2 lbs sweet potatoes into large pieces, and place into salted water.
- Continue boiling until soft (easily pierced by a fork), and then drain.
- Add salt and pepper to taste, 3 tablespoons ghee, and 1/4 cup whole milk to drained sweet potatoes and mash until smooth.
- Season with desired herbs or toppings.
- Serve and enjoy!
For more delicious recipes like these (such as Kale and Sweet Potato Salad, Honey Mustard Ribs, Matcha Chia Pudding, and many more), please check out our cookbook for a guide to doing an elimination diet and lectin sensitivity!