How I Made and Appreciated Natto

Posted on by Jesse Santiano, M.D.

This article discusses how I made my first batch of natto. I figured that with all the health benefits I learned about natto and nattokinase, I would be crazy not to take it. I don’t know any store or restaurant that sells it around my area, so I decided to make my own.

It was easy, and my first batch met my expectations. I will also include some tasting notes here and the other surprising effects of the bacteria responsible for the fermentation, Bacillus subtilis, on the human gut and the environment.

Natto is a traditional Japanese food made from fermented soybeans. Nattokinase is the enzyme extracted from it that has tons of health benefits.

There is a misconception that soy foods can increase breast cancer risk. That is not true. Many studies have proven that – Soy Foods Do Not Increase Breast Cancer Risk.

What you need for natto making

I used the following. Products in orange contain Amazon affiliate links, and I earn a few cents if you buy them.

I reproduced the instructions here from Takahashi Nattomotto

Soybeans 1kg, Sterilized water 10ml,
One spoon of Nattomoto powder (0.1g) – A special spoon is in the box.

  1. Wash the soybeans and soak them for 9 hours (Summer) to 12 hours (Winter). The amount of water should be four times as much as the beans by weight. I started with 165 gm of beans and 660 ml of water

  2. Drain and boil the soybeans for 9 hours on the stove (or use a pressure
    cooker) till the soybeans are soft. I used an electric pressure cooker on “high” for 40 minutes. Put an inch of water inside the pressure cooker. I steamed the beans rather than boiled them. I put a folding stainless steel strainer inside the pressure cooker. You will know the beans are done if they are easy to crush with your fingers. If you use the pressure cooker, please follow the directions.

  3. While the pressure cooker is cooling down, I boil water for sterilization. The amount should be enough to cover the bottom of the pan and the other utensils, like two spoons, a Stainless Steel Slotted Spoon, and a small bowl where you will dissolve the starter. Sterilization is needed because the beans will be in an environment conducive to bacterial growth. You don’t want any other germs there. 

  4. Transfer the beans to the pan. Use three tablespoons of the water where the beans were boiled and put them on the pan for moisture.

  5. Dissolve one spoon of Nattomoto spores (0.1g) in the sterilized water 10ml. This will activate the spores of the Bacillus so that they will start the fermentation. The box contains a small spoon wrapped in paper.

  6. Put Nattomoto solution on the beans and stir them up carefully with a
    sterilized spoon. (Beans are still warm.)

  7. Put the beans in a pan. Do not put a lot of beans in one container. Three layers in each container at the most. If you drop beans on the table, DO NOT put them in the container. Every process has to be clean.

  8. Put a sterilized cloth on the container and put on a lid. I used the technique of Natto Dad on YouTube.  I put cling wrap at the surface of the beans and poked them many times with a toothpick. Another layer of cling wrap is placed on top of the pan and poked again with the toothpick. This technique retains moisture and temperature inside the container.

Another reason why the cling wrap is needed is to keep in the ammonia that the Bacillus produces. Ammonia prevents other bacteria from growing. The holes allow oxygen that the Bacillus needs to survive to enter.

  1. I preheat the oven to 100F degrees (38C) while waiting for the water to boil. I connected the ceramic heater to the thermostat controller. Make sure to push the “on” button on the bulb holder, or the heater will not turn on. The controller stays outside the oven.

  2. Place the container in a 100F(38C) to 103F(40C) degree oven or warmer. Let the natto ferment for 22 to 24 hours.

  3. Remove from the oven (or the warmer), remove the lid (keep the cloth in
    place), and put it in a refrigerator for one night. Then, natto is done.

Caution!!
A. Every Process and all cooking instruments have to be sterilized. I put boiled water on a prewarmed Pyrex and poured it slowly to prevent thermal shock and shattering the glass. Read How to Make Sure Your Pyrex Doesn’t Shatter

B. You can make sterilized water at home. Boil the water for 5-10 minutes, cool down and use it for the process.

Natto Taste

After 22 hours, the natto was done. I was expecting an ammonia smell but did not notice it. It has a faint smell of roasted coffee and chocolate. It is nutty and has a soft cheese taste and texture.

The feel in the mouth is like boiled okra. Mixing it in a bowl with a chopstick will make the strands thicker the more you stir. The Japanese call it neba-neba, a term for slimy foods considered healthy.

The slime contains the spores of Bacillus Subtilis. The spore form allows the Bacillus to survive extreme conditions or when food is scarce. I will tell you later in this article why that is good.

I put the freshly made natto on steamed rice and added soy sauce, chopped green onions, and onions. I had seconds. It’s that good. I will eat them every day.

I guess perspective helped me accept the sliminess easier. Knowing that natto has nattokinase that lowers blood pressure, sugar, and triglycerides and decreases atherosclerosis helped.

Natto also contains high amounts of vitamin K2 which removes the calcium from atherosclerosis to deposit in the bones and teeth.

Plus, I like eating boiled okra.

How natto prevents glucose spikes

Eating the natto with rice gave me a new understanding of how it prevents Post-Prandial Hyperglycemia (PPG) or glucose spikes.

Glucose spikes can injure the lining of the arteries and initiate or worsen atherosclerosis. I noticed that the gooey stuff mixes with the rice too. The slippery beans and rice are quite easy to swallow even when whole.

That makes the digestion of the beans slower, and the release of simple sugars like glucose becomes longer and prevents a sudden increase in blood glucose and insulin levels.

Taniguchi-Fukatsu et al. observed lower glucose after eating viscose foods like natto. Maybe my observation could help explain their results.

Bacillus subtilis: a great microbiome.

The short video, Natto, the power of Life, showed how B subtilis outgrew another bacteria E. Coli. B subtilis also has enzymes that can degrade Reactive Oxygen Species like hydrogen peroxide in the intestines, allowing the other good bacteria to proliferate. 

A study published in Beneficial Microbes showed a decrease in pro-inflammatory bacteria and an increase in anti-inflammatory bacteria in healthy children with a Bacillus Subtilis DE111 probiotic supplement.

A study from Thailand showed that Bacillus subtilis probiotic supplementation eliminated more than 95% of the total S aureus colonizing the human body without
altering the microbiota.

That is relevant when Methicillin Resistant Staphylococcus (MRSA) skin infections abound. MRSA infections are difficult to treat and have a tendency to recur.

How much natto is needed to get the health effects?

According to the Japan Nattokinase Association, a 50 gm pack of commercial nattokinase contains 2,000 FU. FU is Fibrin Degradation Units, and it indicates nattokinase activity level.

Kurosawa et al. found that with a single dose of oral NK at 2000 FU, evidence of clot dissolution, like fibrin degradation products and d-dimer.

Cobos et al. showed that 2,000 FU lowered fasting insulin and glucose levels and the HOMA index. Homeostatic Insulin Assessment (HOMA) quantifies insulin resistance and the function of the pancreatic beta-cells that secrete insulin.

Bacillus subtilis is good for plants

Clean-up of the utensils in contact with natto may be a new experience to some because of the slime. That slime contains Bacillus spores which are suitable for plants.

In a review from the Saudi Journal of Biological Science, the Bacillus species are a significant type of Plant Growth Promoting Rhizobacteria that could benefit plants and perform the same role as chemical fertilizers and pesticides, acting as a biofertilizer and as a biopesticide. 

In an article in Gardener’s Path by Helga George, Ph.D., she said,

Bacillus subtilis can act directly against other microbes by producing a variety of antibiotics that affect fungi or bacteria. They can also act indirectly by stimulating the plant to activate its own defense mechanisms, so it can fend off attacking microbes.

This combination of activities results in a powerful biocontrol agent that is sold commercially to inhibit a number of pathogens on many different crops.

That knowledge made me use the water I used to rinse the kitchen utensils and pour them into my garden.

Natto can be used in many dishes. Iron Chef Japan has two episodes on natto. One with Iron Chef with Rokusaburo Michiba and another with Masaharu Morimoto. You can get a lot of ideas from them. 

There are other ways to make natto, like in an instant pot or a yogurt maker. I watched and learned from Natto Dad.