What Is Natto? Nattokinase, Vitamin K2, Poly-γ-Glutamic Acid & Probiotics Explained

What Is Natto and How Is It Fermented?

Natto is a traditional Japanese fermented soybean food that has been enjoyed for generations. It is made by fermenting steamed or boiled soybeans with natto bacteria, creating its distinctive aroma, flavor, and characteristic sticky texture.

Nattokinase is one of the best-known components associated with natto, but natto contains a variety of other nutrients and compounds as well.

In addition to soybean-derived protein and dietary fiber, natto contains vitamin K2, poly-γ-glutamic acid, and other components associated with the fermentation process.

Another important part of natto is the microorganism used to make it: natto bacteria (Bacillus subtilis var. natto).

Rather than simply thinking of natto as “a fermented food that seems healthy,” understanding how it is made and what it contains offers a more interesting way to look at this familiar Japanese food.

What Is Poly-γ-Glutamic Acid, the Compound Behind Natto’s Sticky Texture?

When natto is stirred with chopsticks, long, pale strands begin to form. One of the main compounds involved in this distinctive sticky texture is poly-γ-glutamic acid (γ-PGA).

Poly-γ-glutamic acid is a high-molecular-weight compound made from many linked molecules of glutamic acid, an amino acid. It is produced by natto bacteria during the fermentation process.

The sticky texture of natto involves poly-γ-glutamic acid along with several other components, which together contribute to natto’s unique consistency and texture.

Because poly-γ-glutamic acid has properties such as water retention, it has been studied and used in a variety of fields, including food, cosmetics, and material science.

Research on Poly-γ-Glutamic Acid and Calcium

In the field of nutrition, researchers have also investigated the relationship between poly-γ-glutamic acid and calcium absorption.

In a small human study involving 24 healthy postmenopausal women, calcium absorption was reported to be higher when 60 mg of poly-γ-glutamic acid was consumed together with calcium as a single dose.

This study specifically examined calcium absorption following a single intake of poly-γ-glutamic acid under defined study conditions. It is one interesting piece of research for understanding the relationship between compounds found in natto and nutrition.

What Is Nattokinase? An Enzyme Produced During Natto Fermentation

One of the most widely recognized compounds associated with natto is nattokinase.

Nattokinase is a proteolytic enzyme produced by natto bacteria as soybeans ferment.

Nattokinase and poly-γ-glutamic acid have different characteristics.

• Poly-γ-glutamic acid: A high-molecular-weight compound involved in natto’s sticky texture
• Nattokinase: An enzyme produced by natto bacteria during fermentation

Research on nattokinase has explored its relationship with blood coagulation, fibrinolytic processes, blood pressure, and other cardiovascular-related factors. More recently, studies have also evaluated findings from multiple clinical trials.

Because study populations, intake amounts, study duration, and other conditions vary, it is important to interpret each study within the conditions in which it was conducted.

For everyday eating, natto can be better understood as a fermented soybean food containing a wide range of nutrients and fermentation-related compounds, rather than focusing on nattokinase alone.

Vitamin K2 in Natto and Bone Health

Another notable characteristic of natto is its high content of vitamin K2.

Vitamin K exists in several forms, and natto is particularly rich in menaquinone-7 (MK-7), a form of vitamin K2.

Vitamin K is an essential nutrient involved in normal blood clotting and also plays an important role in bone health.

Bone contains a protein called osteocalcin, and vitamin K is required for this protein to function normally.

Along with nutrients such as calcium and vitamin D, vitamin K is recognized as one of the nutrients that supports normal bone health.

Natto also contains other compounds, including poly-γ-glutamic acid, that have been studied in relation to calcium and bone-related nutrition. The combination of different nutrients and fermentation-derived compounds is one of the interesting characteristics of natto.

Natto and Warfarin: An Important Interaction to Know About

One important consideration with natto is its interaction with warfarin.

Warfarin is a medicine that reduces blood clotting by interfering with the action of vitamin K.

Natto contains a high amount of vitamin K, and natto bacteria are also involved in vitamin K production. As a result, eating natto may reduce the effect of warfarin.

People taking warfarin need to avoid eating natto. Simply separating the timing of natto and warfarin is not considered sufficient to avoid this interaction, so follow the dietary advice provided by your doctor or pharmacist.

If you are receiving medical treatment or taking medication, it is also a good idea to speak with your doctor or pharmacist before making major changes to your diet or supplement routine.

Is Natto a Probiotic?

As you learn more about natto, you may start to wonder: “If natto is a fermented food, does that mean it is a probiotic?”

Natto is made by fermenting soybeans using natto bacteria. However, fermented foods and probiotics have different definitions.

According to an international expert consensus, fermented foods are defined as foods made through desired microbial growth and enzymatic conversions of food components.

Natto, yogurt, miso, kimchi, and many other foods are well-known examples of foods produced through the activity of microorganisms.

Probiotics, on the other hand, are defined as specific live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.

For this reason, when evaluating a microorganism as a probiotic, factors such as the specific strain, the amount used, and the research conducted on that microorganism are important.

Natto bacteria have also been studied in research exploring the relationship between microorganisms and human health.

Learning how natto is fermented can therefore be a useful starting point for exploring the relationship between microorganisms and our diet, including natto bacteria, lactic acid bacteria, bifidobacteria, gut microbiota, and probiotics.

Tips for Including Natto in Your Everyday Diet

Natto combines the nutritional qualities of soybeans with characteristics created through fermentation.

It can be enjoyed as one part of a varied everyday diet and combined with many other foods.

When including natto in your meals, you may want to keep the following points in mind:

• Combine natto with a variety of foods such as vegetables, eggs, and seaweed
• Focus on the balance of your overall diet rather than relying heavily on one food
• If you are watching your sodium intake, adjust the amount of sauce or seasoning used
• If you have a soy allergy, check the ingredients carefully
• If you are receiving medical treatment or taking medication, follow any dietary guidance provided by your healthcare professional

The key is to enjoy natto in a way that suits your own diet, preferences, and individual needs.

Summary: Natto Is a Fermented Food With a Variety of Components

Natto is a traditional Japanese fermented food made by fermenting soybeans with natto bacteria.

In addition to the well-known nattokinase, natto contains poly-γ-glutamic acid, vitamin K2, soybean-derived protein, dietary fiber, and a variety of other components.

Some fermentation-related compounds have been studied in relation to calcium absorption, blood coagulation, fibrinolytic processes, and other areas. When looking at this research, it is important to consider factors such as the study population, amount consumed, and study duration.

Fermented foods and probiotics also have their own distinct definitions and characteristics.

Learning about natto and the fermentation process can open the door to a broader understanding of the relationship between microorganisms and food, including natto bacteria, lactic acid bacteria, bifidobacteria, and the gut microbiota.

Important Note

This article is intended to provide general educational information about natto, natto bacteria, nattokinase, poly-γ-glutamic acid, vitamin K, fermented foods, and probiotics. It is not intended to diagnose, treat, cure, or prevent any disease. If you are receiving medical treatment, taking medication, or following dietary instructions from a healthcare professional, consult your doctor or pharmacist before making changes to your food or supplement intake.

References

1. Marco ML, et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nature Reviews Gastroenterology & Hepatology. 2021.
2. NIH Office of Dietary Supplements. Vitamin K Fact Sheet for Health Professionals.
3. Tanimoto H, et al. Acute effect of poly-gamma-glutamic acid on calcium absorption in post-menopausal women. Journal of the American College of Nutrition. 2007;26(6):645-649.
4. Nattokinase Supplementation and Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
5. Pharmaceuticals and Medical Devices Agency (PMDA), Japan. Information on Warfarin and Foods Including Natto.