Natto Guide: Nutrition, Benefits, Side Effects, and More
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What Is Natto? A Complete Guide

What Is Natto? A Complete Guide
Wako Megumi/iStock; Canva
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Updated on October 2, 2025
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People in Japan have been eating natto for thousands of years.

 Yet this nutrient-packed superfood has recently captured global attention on social media for its many health benefits — not to mention its distinctive taste and texture.

What Is Natto?

Natto is a traditional Japanese food made from fermented soybeans that has a sticky, gooey texture, umami taste, and potent smell. It looks like a stringy clump of beans.

“It’s certainly an acquired taste for North American taste buds, but in Japan it’s eaten at any and all times of day,” says Jennifer Akimoto, RD, a registered dietitian of Japanese heritage who is based in Ontario. “With its many health benefits, you may want to consider adding it to your diet, too.”

Types of Natto

In the United States, you can purchase natto at Asian grocery stores or make it at home. There are three different types.

  • Otsubu This kind of natto is made from larger soybeans, and is typically moderately sticky. It can be served as a main or side dish. Natto made this way is more pungent, creamy, and chewy.
  • Kotsubu Stickier than otsubu, kotsubu pairs well with rice. It is made from smaller soybeans than otsubu and has a milder flavor.
  • Hikiwari Made with crushed soybeans, this type of natto has a smooth texture. It can be used to make maki rolls.

“They all vary slightly in flavor and texture, so try a few before you decide if you like it or not,” says Akimoto.

Natto Nutrition Facts

Like other fermented foods, natto contains “good” bacteria. Studies show a diet high in fermented foods enhances the diversity of gut microbes and decreases molecular signs of inflammation.

Natto offers other health benefits as well. “It has a lot of nutrition packed within a small serving,” says Melanie Marcus, RD, a registered dietitian from the greater Charlotte, North Carolina, area. “It’s a great source of protein for vegans or anyone trying to follow a plant-based lifestyle.”

A 100 gram (g) serving (roughly ½ cup) of natto contains the following nutrients:

Nutrient
Amount
Daily Value (DV)
Calories
211
10.5%
Protein
19g
38%
Fat
11g
16.5%
Carbohydrates
13g
10%
Fiber
5.5g
20%
Sugars
5g
10%
Calcium
217mg
22%
Iron
9mg
50%
Potassium
729mg
16%
Sodium
7mg
<1%

Potential Health Benefits of Natto

Natto is a nutrient-dense food that’s associated with several health benefits. One of its superstar nutrients is vitamin K, a fat-soluble nutrient essential for blood clotting and bone health.

“It’s considered the richest source of vitamin K2,” says Jon Lanman, RD, a registered dietitian in Bend, Oregon. He says most vitamin K in the Western diet comes in the form of vitamin K1, which is primarily found in leafy green vegetables.

 Vitamin K2 is found in fermented foods and some animal products, and it’s also produced by gut bacteria.

May Strengthen Bones

Vitamin K activates proteins that help build and maintain bones.

 One study found that supplementation with vitamin K reduced the risk of bone fractures, while other research suggests it also may slow age-related loss in bone mineral density in postmenopausal women.

It’s important to note that supplements may contain much higher doses of vitamin K than natto, so it’s not clear if the soybean food would have the same effects as the doses used in research studies.

Beneficial for Heart Health

Nattokinase, the active ingredient in natto, is believed to have benefits for heart health, and research has found it can help dissolve blood clots.

 Other studies have found that supplementation with nattokinase was associated with reduced blood pressure.

 A high intake of vitamin K2 is linked to a lower risk of heart disease, since it helps keep arteries supple.

May Improve Digestion

As a fermented food, natto contains probiotics that support good bacteria in the gut, says Mary Sabat, RDN, a registered dietitian-nutritionist in Georgia. Natto may help control the bacterial balance in the intestines, which can help with GI symptoms, including diarrhea and constipation.

Can Natto Help With Weight Loss?

While consuming any one food doesn’t directly lead to weight loss, experts say natto can certainly be part of a healthy diet if you’re looking to shed a few pounds. One study found that nattokinase assisted with weight loss for women who have obesity and diabetes.

Natto is high in protein and fiber, which Akimoto calls a “hunger-crushing combo.” Feeling satiated after meals can lessen the desire to munch on unhealthy snacks.

Additionally, fermented foods could make it easier to lose weight. According to one research review, improving the health of your gut microbiome is associated with a significant reduction in body mass index (BMI), weight, and fat mass.

How to Select and Store Natto

“When selecting natto at a store, look for a package that has a good expiration date, as natto can spoil quickly,” Sabat says. According to one manufacturer, jars of natto should be used within four to seven weeks of purchase, and consumed within two to three weeks of opening.

 Store-bought natto may be packaged at room temperature or frozen.

“Make sure to thaw natto before eating it,” Akimoto says.

Natto should be stored in the refrigerator in an airtight container, Sabat says.

How to Eat Natto

In Japan, natto is a popular breakfast food, but it can be enjoyed any time of day, Akimoto says.

“If you’re having it for the first time, try it on top of rice or toast with a sprinkle of green onions on top,” she recommends. “This is how it’s traditionally eaten in Japan.”

It’s considered good practice to stir natto before eating. “Experienced natto eaters would tell you to stir the natto at least 100 times before you eat it in order to develop the ‘froth’ and umami flavor,” Akimoto says.

Health Risks of Natto

Natto is generally considered safe for most people to eat, but some people may experience digestive issues such as bloating and gas, Sabat says.

Since natto is made from fermented soybeans, it is not appropriate for anyone with a soy allergy, Marcus notes.

Japanese research found that it’s possible for people without a soy allergy to be allergic to natto, but this is very rare.

Tips for Making Your Own Natto

If you want to make natto at home, you will need soybeans and Bacillus subtilis, a bacteria starter. You can also use natto from a previous batch as a starter for the next batch.

“It’s a set-it-and-forget-it prep style that takes about two or three days from start to finish,” says Sabat.

First, you’ll cook the soybeans in an Instant Pot, pressure cooker, or on the stove. After draining them, you’ll add the bacteria starter (or natto from a previous batch) and let the mixture ferment for 24 hours in a fermentation box or yogurt maker at 40 degrees C (about 104 degrees F). The next day you’ll need to move the natto to the fridge to continue its fermentation for another 24 hours before it’s ready to eat.

The Takeaway

  • Natto is a nutrient-dense traditional Japanese food made from fermented soybeans. It has a sticky texture, an umami taste, and a strong smell.
  • Natto may be beneficial for your bones, heart, and digestive system. It’s a good source of vitamin K2, and it also contains fiber, which makes it a healthy food choice if you’re trying to lose weight.
  • Natto can be made at home or purchased in Asian grocery stores. Pay attention to the expiration date on the label, and store it in the refrigerator in an airtight container.

Common Questions & Answers

What does natto taste like?

Natto has a strong, savory flavor that can vary by batch and fermentation. It’s described as having an umami taste, and the flavor is considered earthy, salty, and bitter.

Yes. Made from fermented soybeans, natto is a great source of fiber, calcium, and vitamin K2, which has been linked to better bone and heart health. It also contains probiotics that are beneficial for digestion.

There are several compounds that make up natto’s sticky texture, including amino acids, the building blocks of protein, and fructan, a type of carbohydrate found in certain plants.

Yes, its sticky, gooey texture is the result of the fermentation process.

Natto is a popular breakfast dish in Japan, but it can be consumed anytime. It can be eaten on its own, but it’s commonly served over rice or on toast with green onions on top.

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Afzaal M et al. Nutritional Health Perspective of Natto: A Critical Review. Biochemistry Research International. October 21, 2022.
  2. What Is Natto? The Benefits of Natto and More. U.S. Soy. November 20, 2023.
  3. Wastyk HC et al. Gut-Microbiota-Targeted Diets Modulate Human Immune Status. Cell. August 5, 2021.
  4. Natto. U.S. Department of Agriculture Food Data Central. April 1, 2019.
  5. Vitamin K. MedlinePlus. January 19, 2023.
  6. Ingold CJ et al. Phytonadione (Vitamin K1). StatPearls. June 5, 2023.
  7. Top Benefits of Vitamin K. Cleveland Clinic. December 7, 2022.
  8. Tsugawa N et al. Vitamin K Nutrition and Bone Health. Nutrients. June 27, 2020.
  9. Ahmad SS et al. Effect of Vitamin K on Bone Mineral Density and Fracture Risk in Adults: Systematic Review and Meta-Analysis. Biomedicines. May 1, 2022.
  10. Ma M et al. Efficacy of Vitamin K2 in the Prevention and Treatment of Postmenopausal Osteoporosis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Frontiers in Public Health. August 11, 2022.
  11. Chen H et al. Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases. Biomarker Insights.
  12. Jensen GS et al. Consumption of Nattokinase Is Associated With Reduced Blood Pressure and Von Willebrand Factor, a Cardiovascular Risk Marker: Results From a Randomized, Double-Blind, Placebo-Controlled, Multicenter North American Clinical Trial. Integrated Blood Pressure Control. October 13, 2016.
  13. Hariri E et al. Vitamin K2 — a Neglected Player in Cardiovascular Health: A Narrative Review. Open Heart. November 2021.
  14. Cobos LM et al. SAT-618 Nattokinase to Improve Insulin Sensitivity and Weight Loss in Women with Obesity +/- Diabetes. Journal of the Endocrine Society. May 8, 2020.
  15. Noor J et al. Exploring the Impact of the Gut Microbiome on Obesity and Weight Loss: A Review Article. Cureus. June 25, 2023.
  16. FAQs. NYrture New York Natto.
  17. Kurotori I et al. Scallop Aquaculture Has a Potential Risk of Natto-Induced Hypersensitivity Reactions in a Local Area of Northern Japan. Allergology International. January 1, 2023.
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Jennifer K. Frediani, PhD, RD, ACSM-CES, is a nutrition scientist, exercise physiologist, and registered dietitian with over two decades of experience in clinical research, education, and lifestyle intervention. She's an assistant professor, research track, at the Nell Hodgson Woodruff School of Nursing at Emory University, adjunct faculty in the nutrition and health sciences program at the Rollins School of Public Health, and a member of the Winship Cancer Institute.

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