Nattō, a traditional Japanese fermented soybean dish, is surging in global popularity as export figures show Japanese shipments of the food have tripled since 2017.
The sticky, slimy breakfast staple has gained massive traction across the Western hemisphere, powered by TikTok taste test videos that have racked up hundreds of thousands of views.
Forget kombucha, miso, and matcha. Nattō has become the latest Asian superfood export to turn into hot property at Asian supermarkets everywhere, despite being considered one of the world's most polarising breakfast foods due to its unpleasant ammonia-like smell.
In Japan, the dish is eaten by nearly 80 per cent of the population, usually served cold over a bowl of steaming rice, often with a raw egg. For centuries, it has been hailed as a nutritional powerhouse linked to a reduced risk of stroke, bone diseases, and tooth loss.
While a growing body of scientific research appears to support these health benefits, medical experts have told the Daily Mail that the dish poses significant risks for specific cohorts of people, raising questions for Western consumers considering swapping their scrambled eggs for breakfast nattō.
History and traditional preparation of nattō
First introduced in Japan during the 700s, nattō grew into a popular dish among aristocrats and warriors during the 1100s. Between the 1300s and 1500s, it served as an important component of Buddhist vegetarian cuisine alongside tofu.
By the Edo period, which ran from 1603 to 1867, nattō had become a staple in most Japanese households. It featured regularly in cookbooks and was usually prepared at home.
To make the dish, soybeans are soaked in water, boiled or steamed, and blended with bacteria to ferment them. Historically, the beans were then wrapped in straw and left to ferment for about a day, depending on the season and ambient temperature.
Today, nattō can be purchased ready-made from convenience stores and supermarkets across Japan. In the UK, it is often sold at Japanese or Asian supermarkets and can also be ordered online, where around 100g of the beans, representing two servings, costs around £5.
Shop-bought nattō usually comes packaged in small, single-serving polystyrene foam containers alongside tiny packets of soy sauce and hot mustard, and is eaten cold.
Nutritional profile and key vitamins
A standard 50g serving of nattō is considered a dieter's friend due to its low calorie count of 110, while packing in 10g of filling protein with virtually no salt.
Another major benefit is its 5.4g of fibre, which is the equivalent of roughly two bananas and represents a fifth of a person's recommended daily intake.
The dish is also exceptionally rich in key micronutrients, including calcium, potassium, iron, manganese, and vitamin K2, as well as vitamin B6 and vitamin E. These nutrients support bone health, blood flow, skin elasticity, and oral health.
Dr Soumaya Zinet, a dentist based in London, explained that the food's reputation as a nutritional powerhouse comes from its impressive combination of protein, fibre, healthy fats, vitamins, minerals, and other naturally occurring compounds contained in a relatively small serving.
"They're all found in a relatively small serving," Dr Zinet said. "Nattō is particularly rich in MK-7, a form of vitamin K2. Vitamin K is needed for normal blood clotting and also contributes to the maintenance of normal bones."
Dr Zinet added that the fermentation process produces nattokinase, an enzyme that has been studied for its possible role in breaking down fibrin, a protein found in blood clots.
Heart health benefits and blood pressure
Fermented foods are widely known for helping to fuel and create healthy bacteria in the gut, which are microbes linked to the prevention of a host of chronic diseases. However, the benefits of nattō appear to extend far beyond the digestive system.
Research shows the dish can help improve heart health, strengthen bones, and lower blood pressure. Clinical studies have demonstrated that nattokinase can help break down blood clots and support healthy blood circulation.
A 2022 research paper from scientists in Pakistan found that eating the fermented beans could help lower and manage high blood pressure.
A long-term study published in the British Medical Journal in 2020, conducted by researchers at the National Cancer Centre in Tokyo, found that men and women who ate fermented soy-based foods such as nattō daily reduced their risk of dying from a stroke or heart attack by 10 per cent.
Nattō's uniquely high levels of vitamin K2 also hold impressive benefits for bone health. Studies on postmenopausal women have shown that regular nattō intake both improves bone mineral density and helps to prevent bone fractures.
These high levels of key bone-strengthening nutrients also have an indirect effect on teeth, according to Dr Zinet.
"Nattō provides calcium and phosphorus, which are important components of bones and teeth," Dr Zinet said. "Vitamin K also contributes to normal bone health. This matters because our teeth depend on healthy bone around them."
Medical warnings and health risks
For many potential consumers, the main deterrent to eating nattō is likely to be its relatively strong smell and sticky texture, which can take some getting used to.
However, experts warn that certain individuals should steer clear of the fermented beans regardless of their health benefits.
"Of course, anyone with a soya allergy should avoid nattō, and like other beans, it can cause temporary bloating or wind, particularly if someone is not used to eating them," Dr Zinet said.
"But the main medical caution is for anyone taking warfarin or another vitamin K antagonist. Nattō is very high in vitamin K, so anyone taking these medicines should speak to their doctor before making a significant change to how much natto they eat."
An overdose of vitamin K can cause serious health issues, including liver problems, difficulty breathing, and problems with blood clotting.
Finally, Dr Zinet pointed out that nattō's sticky consistency poses specific challenges for individuals with dental work.
"Finally, because nattō is sticky, it can be harder to clear from around fixed braces or other dental appliances," Dr Zinet said. "Rinsing with water after the meal and cleaning carefully will help remove any remnants."
