Discover Natto: Japan's Secret Soybean Superfood

It’s no secret that health and wellness has been a huge global trend in the food and restaurant industry for the last few decades. As part of this, there’s been a massive growth in the number of fermented foods available on the market and growing conversation around their health benefits.

Fermented foods are said to have benefits for gut health, brain function, the immune system, skin and even weight loss. Foods like kimchi and kombucha are probably two of the best-known fermented food trends to hit Europe. But what about Japanese natto?

What is Natto?

Hailing from Asia, these Japanese fermented soybeans have been eaten there for thousands of years, usually as a breakfast meal with soy sauce, mustard, chives and rice – and sometimes even raw egg. Washoku (Japanese cuisine) has a long history of pairing soybeans with rice, but natto hasn’t quite taken off in the rest of the world in the way that some other Japanese food exports, like sushi and sake, have done. It’s pronounced as not-TOE in Japanese, with the first character meaning 'to offer' and the second meaning 'bean'.

The dish comes with a lot of nutritional and health benefits for the heart, cholesterol and blood pressure. It’s also a great way for those following a plant-based diet to get protein and nutrients. The word 'superfood' is used a lot in the industry, but with natto it seems justified, particularly with Japan’s reputation for having some of the longest life expectancies in the world, and the Japanese diet contributing to this.

There are over 700,000 tonnes of natto made in Japan each year, and over 7.5 million packets sold throughout the country. According to reports in Japan Today, natto is currently more popular than ever in Japan, seeing a jump of 20% in consumption from last year. There are even – completely unsubstantiated – rumours that the natto fermented soybeans may be beneficial against coronavirus, after reports that the areas of Japan that consumed the most natto had the lowest numbers of confirmed cases.

Health Benefits of Incorporating Natto Into Your Diet

1. Rich in probiotics

One of the main reasons that fermented foods are growing so much in popularity is the fact that they provide a source of probiotics, which can improve gut health, digestion and your immune system. Natto is rich in natural probiotics, bringing all of those benefits with it. It’s even thought to potentially aid weight loss.

2. Packed with protein

One serving of natto provides around 15mg of vegan-friendly, high-quality protein. This is perfect if you’re trying to follow a plant-based diet or reduce your meat consumption, but are struggling to get your protein.

3. Soy sensitive or gluten free? Don’t worry about it

Because of the way that natto fermented soy is made, it’s much easier on the stomach than regular soy. The fermentation process breaks down some of the hard-to-digest proteins that some people who are sensitive to soy can struggle with. Natto is also gluten-free which is helpful for those who avoid gluten in their diet.

4. Get a natural Vitamin K fix

It can be tricky to get Vitamin K – which has blood and heart benefits -  from a natural source, but natto provides this in spades. It also provides Vitamin K2, which is really important for women who want to keep their bones strong and healthy. K2 makes it easier for calcium to move into the bones and helps to move calcium out of the heart and reduce blood pressure.

5. Reduces inflammation

Along with the vitamin K benefits of natto, it can also help to reduce inflammation in the body. Inflammation can be a big problem for a range of health conditions.

6. Load up on calcium and iron

Another benefit for bones, blood and teeth, is that natto is filled with calcium and iron. This is another massive bonus for those for those following a plant-based diet who might find it difficult to get these nutrients from natural sources.

7. Fill up on fibre

Increasing your fibre intake can have some great benefits for digestion and heart health. Surprise, surprise, natto is full of fibre too.

Natto is made by fermenting soybeans with bacillus subtilis, a bacteria that originated as a rice by-product but is now manufactured independently for use in natto making. Natto can be made with other types of beans too – like black beans, adzuki beans, kidney beans and even sunflower seeds - but the bacteria live best in soybeans. The fermentation process creates a unique food that stands out and varies slightly from batch to batch.

There are some other bacillus-fermented foods available in East Asia, South Asia and Africa. In Korea they have a variety of fermented soybean dishes too, the most common being doenjang, which is very similar to natto but without the goodness.

How to Eat Natto

Natto is often described as 'nutty' or 'earthy' with a strong smell and a sticky texture. Some people compare it to the smell and taste of blue cheese. For many western palates – and even some Japanese palates, particularly around Osaka, Kobe and Kyoto where the dish isn’t as commonly eaten – natto is something of an acquired taste. You apparently need to try natto at least four times before you’re hooked.

A recommendation for first-timers is to eat the freshest, small batch natto that’s available, and to eat a small quantity with something familiar whilst you get used to the taste. Some Japanese brands have even developed natto that is seen to be more 'western friendly', by fermenting it in a way that reduces stickiness and odour.

Each of the hundreds of different brands and producers of natto in Japan produce a unique product, and many Japanese people choose their brand based on the tare (soy sauce) that comes with it. In some regions people prefer a sweeter or saltier tare. If you don’t hit the jackpot with your first store-bought natto, then try a different brand to see if you prefer it.

There are three types of natto beans – small, medium and large. The larger beans get less sticky when mixed, so they can sometimes be better for a palate that’s unfamiliar with the texture and taste of the dish. Kimchi, okra or karaage (Japanese fried chicken) and mayonnaise are a few delicious ingredients to combine with natto.

A dish called hikiwari is an option for the brave (or those who are really keen on natto). It’s natto made from soybeans that are crushed before fermentation starts. This creates a bigger surface area for the bacteria to grab onto, making the natto the stickiest and strongest tasting of them all.

If you buy a pack of natto, it usually comes with a small pack of spicy mustard and tare (sweet Japanese soy sauce). Mix up the natto, add your toppings, mix again and then add on top of rice. Serve with condiments like kimchi, soy, spring onion, myoga (Japanese ginger), grated daikon, bonito flakes or nori (seaweed). You can also add it to cold tofu to create a dish called hiyayakko.

In Japan, how natto is eaten varies from region to region. In Hokkaido, they add sugar to natto whereas in Fukushima they often eat it with pickled Chinese cabbage.

Natto should have a white covering on it, which shows the fermentation. Natto that’s a few days old will start to lose this white covering and the beans will become slimier, which can affect the taste. Make sure you store any natto properly.

How Was Natto Discovered?

Because natto has been around for such a long time, it’s difficult to trace how it was first discovered. Most food historians agree that it was probably an accident, whereby some cooked soybeans were left in a bag made from rice straw and left somewhere warm. There’s speculation it was used as a religious offering too,

Farmers used to make their own natto, before enterprising 'natto vendors' in the Edo period started to pop up. These early natto-makers didn’t understand the role of bacteria in the process, so natto was mainly eaten in autumn and winter when the bacteria grew readily. The first commercial natto seller was set up in the 1800s at a small railway station in Ibaraki prefecture. This led to the establishment of the Natto Manufacturers Association of Tokyo.

How to Make Your Own Natto

Nowadays, making natto is relatively straightforward and budget-friendly, provided you have the right type of natto beans and starter. Natto soybeans are usually smaller and have hard seed coats. You need soybeans, water, a natto spores starter or a package of natto bought from a store, a large cooking pot, a sterilised oven-safe dish with a lid and a kitchen thermometer. A pressure cooker such as an Instant Pot can also be used if you have one.

1. Wash soybeans under running water and add them to the pot.
2. Pour fresh water over the soybeans until they’re submerged (about 3 parts water to 1 part beans) and let soak for 9 to 12 hours.
3. Drain the beans, add fresh water and boil for around 9 hours (or about 45 minutes if using a pressure cooker).
4. Once the beans are cooked, drain them and add to the sterilised dish.
5. Follow the instructions on the packet to add the natto starter, or the natto you’ve already bought, and mix it in with the beans.
6. Stir the mixture together using a sterilised spoon and make sure that all of the beans come into contact with your natto starter.
7. Cover the dish and put it in the oven to ferment for 22-24 hours at 100 degrees.
8. Cool the natto for a couple of hours, then age it in the fridge for around 24 hours before you eat it (it can be aged for as long as 90+ hours, or as little as three hours if you’re in a rush).
9. Store your leftovers in the freezer if you want to prolong the life of your natto, otherwise keep it in the fridge.

If you don’t feel quite ready to make your own, you can usually pick up ready-made natto at your local Asian supermarket or at health and natural food shops. You can buy it online too as it’s pretty readily mass produced, though mass produced options often taste quite different to (for want of a better word, since it’s fermented) 'fresh', small batch natto. You can also buy it dried, which has an easier-to-handle flavour profile but doesn’t come with the same health benefits as regular natto does.

One of the other great things about fermented natto is how adaptable it is. It can be added to other dishes like sushi, sandwiches, veggie burgers, pasta, pizza, omelettes, toast or bruschetta to match anyone’s taste. Some people eat natto by itself, but usually it’s eaten with rice or other sides. You can even eat these Japanese fermented beans once they’ve sprouted, making them great as a salad garnish or a side. Natto can be added to a range of Japanese foods like soba, udon, Japanese curry, okonomiyaki, natto miso and tempura.

There are other products made from fermented soy – like tempeh or miso – that are relatively healthy, and easier to find in western restaurants than natto. However, unfermented soy products can sometimes contain harmful compounds, which is why eating fermented soy products makes sense.

Studies 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 in good health. You can even buy nattokinase as a supplement in health-food stores, its benefits are so well-known.

Other Uses of Natto

The feel-good factor of natto doesn’t just stop at eating it either. Natto resin – a by-product of the natto manufacturing process – is being put to use in creating alternatives to plastic packaging for foods and cosmetics, as well as absorbent materials. There’s even talk of using natto resin to support in reforesting desert regions and it’s already been used to clean up the moat of the iconic Osaka castle in Japan. So by eating natto, you can make sure that you’re contributing to sustainability too.

Dishes with Natto or Similar Japanese Foods

One of the other great things about fermented natto is how adaptable it is. It can be added to other dishes like sushi, sandwiches, veggie burgers, pasta, pizza, omelettes, toast or bruschetta to match anyone’s taste. Some people eat natto by itself, but usually it’s eaten with rice or other sides. You can even eat these Japanese fermented beans once they’ve sprouted, making them great as a salad garnish or a side. Natto can be added to a range of Japanese foods like soba, which are thin buckwheat noodles, or udon noodles. They can also make a great addition to Japanese curry or okonomiyaki, which is a cabbage-based savoury pancake that originated in Osaka and Hiroshima, or they can be combined with tempura, a light rice flower batter.

Natto isn’t the only famed Japanese food that is fermented; it’s not even the only soy-based one. Unfermented soy products can sometimes contain harmful compounds, which is why eating fermented soy products makes sense. There are other products made from fermented soy that are relatively healthy and easier to find in western restaurants than natto. Tempeh is a versatile ingredient that can be fried up, stuffed into raviolis, or used as a substitute for meat in stews. Equally as widespread is miso, which is perhaps best known in the form of miso soup. And moving beyond soy, another fermented Japanese concoction to try is kombucha, an infusion of tea, sugars and specific kinds of bacteria and yeasts. If fermentation doesn’t sound too tantalising but you want to wander farther into the world of Japanese cuisine, why not try your hand at a Japanese seafood stew or roll some salmon maki sushi?