Natto: The Fermented Soy Superfood

June 5, 2018

One of the most commonly asked food topics that I field from my readers is about soy, and is it good for you?

The answer is: sometimes. Marketing geniuses have poised soy as the wonder health alternative to virtually everything. In most supermarkets, you’ll find soy milk, soy protein, soybean oil and even soy soap, but the soy in its many forms is not necessarily the health choice that it has been marketed to be.

The problem is that the soy that you are seeing in all these foods is not the traditionally grown crop of Japan. The majority of soy that you find in in grocery stores is actually genetically modified (GMO), and is not farmed the same way or yielding the same nutrition.

However, when you ferment soybeans you have a completely different product that yields a completely different nutrient system for the body. When it comes to soy, the safest (and in my opinion the only) way to consume it is through fermented soy products like miso, tempeh or natto.

What is Natto?

Natto is a traditional food usually consumed at Japanese breakfast tables together with miso soup, fish, and rice. Tofu, tempeh, miso and natto are all whole food forms of soybean.  The key to natto’s health benefits is that it is fermented. Natto is made by soaking whole soybeans, then steaming or boiling them, and afterwards adding the bacteria Bacillus subtilis to the mixture.  It is then allowed to ferment over time. (1)

Natto is known to be a rather acquired taste, probably due to its smell and texture. For many people, the ammonia smell may evoke a mixture of old socks and cheese. As for the texture, it’s resembles a gooey, stringy and sticky small bean, which also adds to its unappealing nature.

People have strong feelings towards natto – they tend to either love it, hate it or eat it until it grows on them. The taste of natto is actually not that bad; it’s the unpleasant smell and stringy texture which can be surprising; it is simply not a texture that our western taste buds and palate are used to.

Natto Nutrition Facts

While natto’s appearance may not leave a very good first impression, its nutrition is well worth giving it a chance.  Natto is as an excellent source of protein, fiber, vitamins and minerals. Additionally, the Bacillus subtilis in natto creates an enzyme called nattokinase, which produces vitamin K2 (more on that later).

Rich in macronutrients and micronutrients, natto is fantastically nutritious, which is why people who regularly consume natto experience a fantastic array of health benefits. It’s the very definition of a “superfood” and contains huge amounts of beneficial nutrients in every serving. Just one cup of natto includes: (2)

  • 371 calories
  • 31 grams protein (62 percent DV)
  • 19.3 grams of fat
  • 25.1 grams carbohydrate
  • 12.3 milligrams sodium
  • 9.4 grams fiber (38 percent DV)
  • 8.6 grams sugar
  • 99.8 milligrams choline
  • 2.7 milligrams manganese (134 percent DV)
  • 15.1 milligrams iron (84 percent DV)
  • 1.2 milligrams copper (58 percent DV)
  • 40.4 micrograms vitamin K (51 percent DV)
  • 201 milligrams magnesium (50 percent DV)
  • 380 milligrams calcium (38 percent DV)
  • 22.8 milligrams vitamin C (38 percent DV)
  • 1276 milligrams potassium (36 percent DV)
  • 5.3 milligrams zinc (35 percent DV)
  • 305 milligrams phosphorus (30 percent DV)
  • 15.4 micrograms selenium (22 percent DV)
  • .3 micrograms vitamin B2/riboflavin (20 percent DV)
  • .3 milligrams vitamin B1/thiamine (19 percent DV)
  • .2 milligrams vitamin B6 (11 percent DV)
  • 14 micrograms folate (4 percent DV)
  • .4 milligrams vitamin B5/pantothenic acid (4 percent DV)
Natto Nutrition

4 Benefits of Natto Nutrition

1. Loaded with Vitamin K Benefits

One of the main reasons natto is so good for you is because it is rich in vitamin K. In fact, the Department of Public Health reports that natto contains 100 times more vitamin K2 than cheese! (3) The importance of K2 is profound because, according to the National Institutes of Health, it is a key component in maintaining the bone mineral density of postmenopausal women suffering from osteoporosis. (4) As described by the George Mateljan Foundation: (5)

There are three basic types of vitamin K. Their common names are K1, K2, and K3. The K1 form of vitamin K is found in plant foods, and many of our best sources of this vitamin are green vegetables (including 16 excellent sources); this makes good sense since K1 is required for green plants to conduct the process of photosynthesis. The K2 form of vitamin K is made from K1 and K3 by bacteria and other microorganisms. It can also be made in the human body through a conversion process involving K1 and K3.

This is especially good news for vegetarians and vegans because vitamin K2 is generally obtained by eating meat and other animal products.

Higher intakes of vitamin K2 are associated with lowered risk of heart disease, artery calcification and all-cause mortality (death for any reason). (6) It also supports bone health by increasing bone mass and slowing bone loss that occurs over time. (7)

Also, because it is fermented, natto has a completely different nutritional makeup from raw soy beans, especially the genetically modified variety. On one hand, when natto is fermented, the soybean loses vitamin A, several other vitamins and minerals, and decreases in calorie content and sodium. But what it gains from the process more than makes up for these nutrition losses. Natto is a superior source of nutrients. (8)

2. Fermentation Benefits from Nattokinase

Due to fermentation, soybean proteins are 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 soy traditionally does is because of the enzyme nattokinase. Created during the fermentation process, nattokinase is used for a variety of medicinal purposes: (9)

3. Contains Powerful Probiotics

Another key to natto’s health benefits is its rich probiotics content. Bacillus subtilis, (also referred to as Bacillus uniflagellatus, Bacillus globigii and Bacillus natto), is the bacteria added to soybeans and then left to ferment in order to create natto. It’s key function is that it produces enzymes, which are used to reduce blood clotting and produces vitamin K and B vitamins. (10) At one point in its history, it was even used as a broad-spectrum antibiotic.

Research reveals that supplemental Bacillus subtilis improves symptoms of irritable bowel syndrome, supports healthy microbiome diversity and helps protect against salmonella infection. (11, 12) In general, though, one benefit of fermented foods like natto is that they support overall health and immunity, often in larger-spectrum ways that can be defined by one symptom or reduced risk of one disease. (13)

4. Carries Important Manganese Benefits

At over 130 percent of the recommended daily intake for manganese, natto can help to support good bone and joint structure throughout your lifetime, given that you’re also consuming plenty of other bone and joint nutrients. (14)

Not getting enough manganese may also lead to a dysfunction in superoxide dismutase activity, a very important antioxidant that helps manage healthy levels of inflammation and oxidative stress throughout the body. (15)

Natto vs. GMO Soy

Although natto can be made with black beans, adzuki beans, kidney beans and even sunflower seeds, the Bacillus subtilis thrives best on soybeans which help to produce nattokinase more efficiently. It is important to note that nattokinase is not found in other non-fermented soy foods, which makes the distinction between natto and unfermented, genetically modified soy very clear.

With that said, while fermented soybeans are a packed powerhouse of goodness, other soy products are packed powerhouses of health risks. For the most part, unfermented soy is full of: (16)

  • Phytates – known to cause tooth decay and stunt growth
  • Trypsin inhibitors – disrupt healthy digestion and can cause pancreatic disorders
  • Goitrogens – thyroid hormone blockers that may cause cancer and hypothyroidism
  • Phytoestrogens – compounds that alter normal estrogen production and may be linked to breast cancer
  • Hemagglutinin – blot clotting agents that can cause hypoxia (low oxygen levels)
  • Aluminum – known to cause Alzheimer’s disease and dementia
  • Vitamin B12 inhibitors – can contribute to vitamin B12 deficiency
  • Genetically modified ingredients – more than 90% of soy grown in the U.S. is genetically modified

Particularly when it comes to GMOs, long-term health risks are truly unknown. There are reports that genetically modified soybeans may impact formation of life-threatening food allergies, cause liver damage, disrupt fertility and alter fetal/childhood development. One human study on consumption of GM soybeans found that the modified genes for herbicide resistance actually transferred into the digestive tracts of participants and continued to function after the beans were digested. (17) On the other hand, though, some reports find that animal testing on GMOs in food only occasionally reveal dangers to health. (18)

Side Effects and Precautions for Natto

Various sources warn that the nattokinase in natto is safe when consumed in food, but it is better to be cautious of it in supplement form, as more research is necessary to prove its safety and interaction with other elements. (19)

Because natto contains a specific type of vitamin K2, known as MK-7, in abundance, it might interfere with blood thinning drugs like warfarin. (20) It’s a good idea to avoid natto if you’re on blood-thinning medications.

Also, at 371 calories per cup, the average adult on a 2,000-calorie diet would take in nearly 20 percent of their daily energy intake in just one sitting! The Japanese aren’t traditionally known as being a culture that struggles with obesity because of their active lifestyle and wholesome diet, but Americans are. If you eat a standard American diet, try to sticking with just a cup a day at the most. This is important, not just for caloric intake, but to protect yourself against getting too much protein (yep, that’s a thing). Too much protein consumption can cause a whole slew of health conditions like kidney stones and osteoporosis, so you definitely just want to make sure you are taking in a good amount for your age and weight.

When it is all said and done, the positive health benefits far outweigh any risk associated with eating natto. Just keep things balanced, eat a wide variety of fruits and veggies and stay away from the GMO soy.

Final Thoughts on Natto

Natto is a fermented, non-GMO soy product that is truly a superfood. In one cup, natto provides huge amounts of vital nutrients for your body, including calcium, manganese, iron, vitamin K, magnesium and more.

The difference between natto and other soy products is the process of fermentation, which is why natto contains plenty of beneficial bacteria that support overall health.

Four major benefits of natto are:

  1. Loaded with vitamin K benefits
  2. Fermentation benefits from nattokinase
  3. Contains powerful probiotics
  4. Carries important manganese benefits

Together, these nutrient combinations mean that natto supports heart health, bone health, lower cancer risk, hormonal disorders, immunity, antioxidant activity and low levels of inflammation.

Natto is somewhat high in calories per serving, so be careful not to overdo it. People on blood-thinning medications shouldn’t take natto because it may impact the function of their medications.

Josh Axe

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