Natto: Japan’s Most Divisive Food — and Why You Should Try It Anyway
By Yoshi | Japan Unveiled
There is a food in Japan that divides the country more cleanly than almost any political question.
The division is not along the lines of age, or income, or education, or urban versus rural background. It is primarily geographic. And it is absolute.
The food is natto — fermented soybeans — and the division is between the Japanese people who eat it daily and consider it essential to their breakfast, their sense of self, and their general wellbeing, and the Japanese people who cannot enter a room where it is being eaten without experiencing a specific quality of physical aversion.
I am in the first group. I have been in the first group since childhood. My mother served natto at breakfast most mornings, and I grew up with its specific smell — the sharp, fermented, slightly ammonia-adjacent aroma that is the first thing anyone who has encountered natto will recognise — as one of the defining smells of morning. It is, for me, the smell of home.
I understand completely that this is not a universally shared experience.
What I want to do in this article is explain what natto actually is, why it smells the way it smells, what it tastes like when you approach it correctly, why the health research on it is genuinely remarkable, and — most importantly — why the specific Japanese debate about natto reveals something interesting about Japan’s relationship with its own food culture.
What Natto Is
Natto (納豆) is whole soybeans that have been fermented using Bacillus subtilis var. natto — a specific bacterial strain that produces the chemical transformations that give natto its distinctive characteristics.
The production process: soybeans are soaked, steamed or boiled until soft, and then inoculated with the natto bacteria and incubated at approximately 40 degrees Celsius for eighteen to twenty-four hours. During incubation, the bacteria multiply, producing enzymes that begin breaking down the proteins and starches in the soybeans and generating the specific chemical compounds — pyrazines, various amino acids, polyglutamic acid — that are responsible for natto’s smell, its characteristic stringiness, and its complex flavour.
The result of this process: soybeans that are softer than raw soybeans, darker in colour, covered in a web of stringy white threads (itohiki — the stringing property) that extend dramatically when the soybeans are stirred or lifted, and with an aroma that is simultaneously deeply fermented and sharply pungent.
The stringiness deserves specific attention because it is one of the most immediately striking physical properties of natto and the property that most surprises first-time encounters. The strings are polyglutamic acid — a biopolymer produced by the bacteria — and they are harmless, flavorless, and entirely part of the correct natto experience. Stirring natto vigorously before eating — the standard preparation — causes the strings to proliferate dramatically, creating a foam-like accumulation of white threads that looks alarming and is, in fact, the sign of well-fermented natto. More stirring, more strings, more fermentation by-products that improve the flavour.
The Smell: An Honest Description
The smell of natto is the most significant barrier to first-time encounters with the food, and I want to describe it honestly rather than defensively.
Natto smells fermented. This is accurate but insufficient. It smells of ammonia — not strongly, not aggressively, but unmistakably. It smells of something biological and active, because it is biological and active; the bacteria are present and the fermentation is ongoing even in the refrigerated container. It has a specific pungency that is different from other fermented foods — different from blue cheese, different from kimchi, different from aged miso — because the specific bacterial strain and the specific substrate produce a specific aromatic profile.
People who grew up eating natto have had this smell encoded as food smell — as the smell of something good and nourishing that is associated with positive memories and positive states. People who did not grow up eating natto encounter the same aromatic profile without that encoding, and their response is frequently the aversion response that the olfactory system produces when it encounters unfamiliar biological smells.
This is not a character flaw in people who find natto aversive. It is a normal neurological response to an unfamiliar fermented food. The same response occurs when people from natto-eating regions of Japan first encounter strong European cheeses, or when people from cheese-eating cultures first encounter durian. The smell is the same smell; the cultural encoding determines whether it signals food or threat.
The practical implication: if you approach natto with the expectation of aversion, you will probably experience aversion. If you approach it with the expectation of a fermented food that you are willing to learn, and with the correct preparation that tempers the most assertive aromatic notes, the experience is considerably more open.
The Regional Divide: East vs. West
The geographic divide in Japanese natto culture is one of the most striking examples of Japanese regional food variation.
Eastern Japan — Tokyo, the Kanto region, the Tohoku region, Hokkaido — is natto country. Consumption rates are high, natto is a standard breakfast item in most households, and the cultural relationship with the food is deeply embedded. Tokyo supermarkets have extensive natto sections with multiple varieties, brands, and styles.
Western Japan — Osaka, Kyoto, Kansai generally — has a historically much lower rate of natto consumption. The Osaka saying “we don’t eat that” (with the specific Kansai tonality that implies mild contempt) is something I have heard from Osaka acquaintances when natto is mentioned. The western Japanese person who does not eat natto is not unusual; the western Japanese person who actively dislikes it is the norm.
The reasons for this geographic divide are partly climatic — the fermentation conditions that produce good natto are more naturally available in the cooler, more humid eastern regions — and partly historical, reflecting the specific agricultural and culinary traditions that developed in different parts of Japan before the railway network made food distribution truly national.
The railway did not eliminate the divide. Even now, with natto nationally available in every supermarket, consumption remains much higher in eastern Japan than western Japan. The divide reflects not just access but the deeply embedded food culture that shapes what people are willing to eat.
How to Eat Natto Correctly
The correct preparation of natto is something that Japanese people disagree about in the specific, passionate way that people disagree about things that are simultaneously personal and cultural.
The baseline preparation: one package of natto (typically 45-50 grams, in a small polystyrene container), stirred vigorously with chopsticks or a small whisk before the provided condiments are added. The vigorous stirring — a minimum of fifty times is often cited, though the actual number is a matter of personal conviction rather than scientific determination — is the crucial step that develops the texture and activates the full flavour profile.
The provided condiments: a small packet of soy sauce and a small packet of karashi mustard are included in most commercial natto packages. The mustard is optional for most Japanese people but genuinely useful for first-time encounters: it adds pungency and heat that partially masks the more challenging aromatic notes of the natto and provides a familiar flavour reference point.
The service: natto is most commonly served over hot rice — the heat of the rice warms the natto slightly and the rice provides a mild, starchy backdrop against which the natto’s complex flavours are more accessible. The combination of natto and rice is one of the simplest and most nutritionally complete meals available in Japanese cooking.
Additional preparations: some people add a raw egg yolk to the stirred natto, which adds richness and slightly mellows the flavour. Some add finely sliced green onion. Some add a small amount of dashi or mentsuyu (noodle soup base). The additions are personal and reflect individual taste rather than any objective correct preparation.
The Health Research: Why Natto Is Worth Taking Seriously
Natto has been the subject of significant scientific interest because the fermentation process produces several compounds that have demonstrated beneficial effects in research.
Nattokinase — an enzyme produced by the natto bacteria that has been studied for its fibrinolytic properties (its ability to break down fibrin, a protein involved in blood clotting). Research suggests that nattokinase may contribute to cardiovascular health by reducing the risk of blood clot formation. The research is ongoing and the clinical evidence base continues to develop, but the early findings have generated substantial scientific interest.
Vitamin K2 (MK-7) — natto is one of the richest dietary sources of Vitamin K2 in its MK-7 form. Vitamin K2 plays roles in bone metabolism and cardiovascular health that are distinct from the roles of Vitamin K1 (found in leafy vegetables). The correlation between high natto consumption in eastern Japan and specific health outcomes has been the subject of epidemiological research.
Probiotics — the live bacteria in natto contribute to the gut microbiome in ways that may support digestive health, consistent with the broader research on fermented foods and gut health.
The health research on natto is not conclusive — it never is, in the complex field of nutrition research — but the direction of the evidence is consistently positive, and the traditional Japanese understanding of natto as a health food has more scientific backing than many traditional food health claims.
The Japanese Debate: A Country Divided by Breakfast
I want to return to the division I began with, because I find it genuinely illuminating about Japanese food culture.
Japan is, by international standards, a remarkably unified food culture. The same dishes appear, in recognisably similar forms, across the country. The same food occasions — the New Year meal, the midsummer barbeque, the autumn mushroom nabemono — are observed nationally. The Japanese national food identity is coherent and strong.
And yet natto divides the country so cleanly along regional lines that Japanese people born in different regions can have genuinely different relationships with a staple breakfast food — different enough that a Osaka person moving to Tokyo may never fully adopt the morning natto that their Tokyo neighbours consider essential, and that a Tokyo person moving to Osaka may find themselves consuming natto in private, like a guilty habit, because the social context of their new environment does not support it.
This is the specific revelation that natto provides about Japan: underneath the surface of cultural unity, the specific, intimate food habits that are acquired in childhood and that are embedded in the earliest sensory memories are remarkably resistant to change. The food you grew up eating is not merely food. It is identity. The smell that your nose learned as a child to encode as home does not re-encode easily in adulthood, regardless of where you subsequently live.
Natto is Japan’s most honest food in this sense: it makes visible the specific, persistent, geographically embedded nature of Japanese food identity in a way that more universally beloved foods cannot.
My Honest Recommendation
Try natto at least once.
Not at the beginning of your first morning in Japan, when everything is already unfamiliar and the sensory overload is already at maximum. After a few days, when you have settled into the specific textures and flavours of Japanese food and your palate has begun to calibrate to the fermented, savoury, umami-forward flavour language of Japanese cuisine.
Buy a small package from a supermarket or a convenience store. Follow the stirring instructions. Add the mustard. Serve over rice. Approach it as a fermented food rather than as a test.
You may dislike it. That is a legitimate outcome. Many Japanese people dislike it. The specific sensory experience is genuinely challenging for people who did not grow up with it.
Or you may find, as many visitors do who approach it correctly, that natto is something genuinely interesting — complex in flavour in ways that the initial aroma does not suggest, satisfying in a specific nutritional and sensory way, and worth understanding as one of the specific things that Japan does with soybeans that no other food culture has replicated.
It smells of fermentation. It tastes of something ancient and functional and specifically Japanese.
That is worth experiencing, even if only once.
— Yoshi 🫘 Central Japan, 2026
Enjoyed this? You might also like: “Miso Soup: The One-Bowl Philosophy That Defines Japanese Cooking” and “Japanese Breakfast: The Meal That Changes How You Think About Mornings” — both available on Japan Unveiled.
