Natto: the Fermented Soy Superfood

A very popular yet traditional dish in Japan, natto is made from fermented soybeans and resembles a gooey, stringy and sticky small bean. It’s also packed with nutrients.

For those who know about it, people typically have strong feelings toward natto — they tend to either love it, hate it or eat it until it grows on them. While the taste of natto is welcome to many, the smell and stringy texture take longer to get used to for many.

When you ferment a soy food like natto, more nutrients are created — similar to fermented foods like miso and tempeh that are all full of gut-supporting probiotics.

So what is natto, and how can it impact your health? Let’s dig in.

What Is Natto?

Natto is a traditional food usually consumed at Japanese breakfast tables together with miso soup, fish and rice.

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The fermentation of natto accounts for many of its health-promoting properties.

It is made by soaking whole soybeans, then steaming or boiling them, and afterward adding the bacteria Bacillus subtilis to the mixture. It is then allowed to ferment over time.

Natto is known to be a rather acquired taste, probably due to its unique smell and texture. It has a distinct, bitter flavor.

In the early 1900s, researchers discovered that the starter culture used to make natto could be produced without the use of straw. This changed the way that it was produced and made it much easier for food manufacturers to begin commercial production of natto, increasing its popularity and making it possible to enjoy all around the globe.

Tofu, tempeh, miso and natto are all whole food forms of soybean.

Nutrition Facts

While natto’s appearance may not leave a very good first impression, its nutrition profile makes it well worth giving it a chance. It is as an excellent source of protein, fiber, vitamins and minerals.

Additionally, the Bacillus subtilis in natto creates an enzyme called nattokinase, which aids in the production of vitamin K2 and helps preserve heart health.

Rich in macronutrients and micronutrients, natto is highly nutritious, which is why people who regularly consume it experience a wide array of health benefits. It’s the very definition of a “superfood” and contains huge amounts of beneficial nutrients in every serving.

A 100 g serving of natto contains approximately:

• Calories: 211
• Total Carbohydrates: 12.7 g
• Fiber: 5.4 g
• Sugar: 4.9 g
• Total Fat: 11 g
• Saturated Fat: 1.6 g
• Polyunsaturated Fat: 6.2 g
• Monounsaturated Fat: 2.4 g
• Trans Fat: 0 g
• Cholesterol: 0 mg
• Protein: 19.4 g
• Sodium: 7 mg (0.3% DV*)
• Copper: 0.667 mg (74% DV)
• Manganese: 1.53 mg (66% DV)
• Iron: 8.6 mg (48% DV)
• Magnesium: 115 mg (27% DV)
• Zinc: 3.03 mg (27% DV)
• Vitamin K: 23.1 mcg (19% DV)
• Calcium: 217 mg (17% DV)
• Selenium: 8.8 mcg (16% DV)
• Potassium: 729 mg (15% DV)
• Vitamin C: 13 mg (14% DV)
• Riboflavin: 0.19 mg (14% DV)
• Phosphorus: 174 mg (14% DV)
• Thiamine: 0.16 mg (13% DV)

*Daily Value: Percentages are based on a diet of 2,000 calories a day.

In addition to the nutrients listed above, natto also contains a small amount of folate, pantothenic acid and sodium as well.

Health Benefits

1. Rich in nutrients

Natto is one of more nutrient-dense foods, including in the three macronutrients that are unusually well balanced. One serving of natto delivers 13 grams of carbohydrates, 11 grams of fat and 19 grams of protein. As such, it’s considered a high-protein food as well as a plant-based protein.

One serving of natto also contains over 5 grams of fiber, making it a high-fiber food as well.

Natto is very high in the minerals copper, manganese, iron, magnesium and zinc.

Foods high in copper can boost both brain and skin health, for instance. Iron-rich foods are needed because iron is a common deficiency and play a role in red blood cell production and energy levels. Magnesium-rich foods play a central role in just about every bodily process, from the synthesis of DNA to the metabolism of insulin.

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It’s also high in vitamin K. In fact, the Department of Public Health reports that it contains 100 times more vitamin K2 than cheese. Vitamin K2 is considered a key component in maintaining the bone mineral density of postmenopausal women suffering from osteoporosis. Natto is one of the few plant-based sources of vitamin K2.

2. Contains nattokinase

Nattokinase is an enzyme that is isolated from natto and credited with supplying many of its potent health benefits. In particular, nattokinase has been shown to help prevent blood clots, promote blood flow and improve heart health.

Created during the fermentation process, nattokinase is used for a variety of medicinal purposes, including heart disease, high blood pressure and muscle spasms.

Although plenty of other fermented soy foods boast a long list of health benefits, natto is the only soy product that contains nattokinase. Additionally, while nattokinase is also available in supplement form to help you get in your daily dose, adding natto to your diet instead can provide a burst of added nutrients and probiotics as well as a hearty chunk of nattokinase in each and every serving.

During the fermentation process, soy becomes more easily digested and absorbed, which is especially good news for those who normally suffer gut issues when eating legumes. One reason natto doesn’t trigger gastrointestinal discomfort like other forms of soy is because of nattokinase.

3. Packed with probiotics to benefit gut health

Another key to natto’s health benefits is its rich content of probiotics. Bacillus subtilis (also referred to as Bacillus uniflagellatus, Bacillus globigii and Bacillus natto) is the bacteria added to soybeans that is then left to ferment in order to create natto. It helps synthesize enzymes, which are used to reduce blood clotting, and produces vitamin K and B vitamins.

Research reveals that supplemental Bacillus subtilis improves symptoms of irritable bowel syndrome, supports a healthy microbiome and helps protect against inflammation.

In general, though, the major benefit of probiotic foods like natto is that they support overall health and immunity to reduce your risk of disease and keep your body in tip-top shape.

Filling up on probiotic foods like natto can help balance the bacteria in your gut to optimize the health of your digestive system. Research shows that disruptions in this delicate gut microbiome can have serious consequences ranging from digestive issues to increased allergy severity and beyond.

Getting plenty of probiotics from food or supplement sources has been shown to be beneficial in the treatment of diarrhea, ulcerative colitis and irritable bowel syndrome, among other issues.

4. Promotes bone health

Natto is loaded with several important micronutrients that play an important part in bone health. Calcium, for example, is one of the main structural components of bone tissue and absolutely essential to preventing bone loss throughout the life span.

Vitamin K is also crucial to bone health, with studies showing that a deficiency of this key vitamin can increase the risk of bone abnormalities like osteoporosis and fractures. Manganese, zinc and copper are just a few other minerals that are plentiful in natto and important when it comes to maintaining bone density.

In addition, a 2020 study published in the Journal of Nutrition found that “natto intake is inversely associated with osteoporotic fracture risk in postmenopausal Japanese women.” Meanwhile, a 2021 systematic review and meta-analysis concluded that “the dietary intake of natto demonstrated an improving effects on the [bone mineral density] of the femoral neck.”

5. Keeps your heart healthy

Topping the charts as one of the most nutrient-dense foods on the planet, it should come as no surprise that squeezing a serving or two of natto into your diet can have a big impact on the health of your heart.

With over 5 grams of fiber packed into each serving, it may help lower cholesterol levels to prevent plaque buildup in the arteries. It’s also high in vitamin K2, which has been linked to a reduced risk of arterial calcification and coronary heart disease.

Plus, studies even show that consumption of nattokinase, the main enzyme found in natto, has been associated with lower blood pressure and decreased blood clotting. Keeping your blood pressure under control can help ease the stress on your arteries and keep your heart muscle healthy and strong.

How to Use

Wondering where to buy natto and how you can add it to your diet? Thanks to its growing popularity, it is now available at many natural food stores and specialty shops. You can also buy it online to have it delivered directly to your door.

Once you get your hands on this powerful superfood, there are plenty of ways to take advantage of the unique natto taste and nutrient profile. Try making a traditional Japanese natto breakfast by combining it with rice and pickled veggies.

Alternatively, you can make a natto roll using your favorite sushi ingredients to give the nutritional profile of your roll a major upgrade. It also works well with miso soup, fish and whatever vegetables you have on hand.

How to Make

Natto can easily be purchased and added to your favorite recipes and dishes. However, if you’re feeling up to the challenge, you can also try making it on your own at home.

Most recipes involve washing and soaking the soybeans for nine to 12 hours, draining them and then boiling for an additional nine hours. The soybeans should then be combined with a natto spore solution and placed into thin layers separated by a cheesecloth.

In a closed container, the natto should then be placed in a dehydrator or oven set to 100 degrees Fahrenheit and allowed to ferment for 22–24 hours. Once the final product is ready, it can be stored in the refrigerator or freezer to extend its shelf life even longer.

Risks and Side Effects

For most people, natto can be safely consumed with minimal risk of side effects. However, more research is still needed on the effects of nattokinase in supplement form as the potential long-term side effects of this supplement still remain unclear.

Because natto contains a specific type of vitamin K2, known as MK-7, it might interfere with blood-thinning drugs like warfarin when consumed in high amounts. For this reason, you should check with your doctor before adding this fermented soy to your diet if you’re currently taking any blood thinners.

Additionally, natto is relatively high in calories. For this reason, it’s important to keep your intake in moderation and pair it with other nutritious whole foods to avoid unintentional weight gain and other adverse side effects.

When it is all said and done, however, the positive health benefits far outweigh any risks associated with eating natto. Just keep things balanced, incorporate a wide variety of other foods into your diet, and swap it in for genetically modified and unfermented soy products in your diet.

Final Thoughts

• What is natto? Produced from boiled soybeans that have undergone fermentation, it is a Japanese staple that is chock-full of powerful health benefits.
• A few of the most impressive natto benefits include improvements in bone health, digestion and heart health. It is also high in protein, fiber and probiotics, as well as important micronutrients like manganese, iron, copper and vitamin K.
• Natto stands out from other soy products because it is fermented, which increases its digestibility and helps your body absorb it better. It also contains nattokinase, a key enzyme that protects against blood clots and comes with a long list of health benefits.
• For best results, try adding natto to your favorite rice and veggie dishes to squeeze more nutrients into your day and enjoy the multitude of health benefits that it has to offer.