Natto — Japan's Most Divisive Food and Why the People Who Love It Are Right

Natto (Bacillus subtilis-fermented soybeans) is one of the most polarizing foods in the world. It is also one of the most nutritionally dense foods available. These two facts are connected — the fermentation process that produces the sticky strings, the ammonia smell, and the intensely complex flavor also produces compounds found in almost no other food.

Understanding natto first requires getting past the description and getting to the actual food.

What Natto Actually Tastes Like

Every description of natto front-loads the negative sensory properties. Here is a more accurate description:

Smell: Ammonia-forward when first opened. Strong. The smell attenuates when the natto is mixed vigorously — mixing changes the chemical structure of some volatile compounds.

Texture: Sticky, with visible fermentation threads (polyglutamic acid) that form strings between the beans. The beans themselves are soft, not mushy.

Flavor: Earthy, slightly nutty, savory with umami depth, slightly fermented sour note in the background. Complex. The tare sauce (soy-based) and karashi (Japanese mustard) served with it add salt and heat that round the flavor significantly.

The key fact: natto tastes different from how it smells. The ammonia smell does not accurately predict the flavor. People who refuse to try it because it "smells bad" are refusing based on inaccurate information about the eating experience.

How to Eat Natto

Standard preparation:

1. Open the package. A packet of tare (liquid soy seasoning) and a packet of karashi (mustard) are typically included.
2. Add the tare and karashi directly into the container.
3. Mix vigorously with chopsticks — 50-100 strokes. The more you mix, the more threads develop and the more the flavor mellows.
4. Serve over hot white rice.

The mixing step is not optional. Natto not mixed properly has a much more aggressive flavor and texture than properly mixed natto.

Add-ins that help new eaters:

• A dash of soy sauce
• Thinly sliced scallion
• Karashi mustard (start with a small amount)
• Grated daikon
• A raw egg yolk mixed in (tones down the intensity significantly)

Why Japanese People Eat It for Breakfast

Natto is quintessentially a breakfast food in Eastern Japan (Tokyo and northward). One small container over rice, with miso soup alongside.

The logic: natto is high protein (18g per 100g), high in probiotics, and requires no cooking. It is also historically one of the cheapest protein sources in Japanese cooking — soybeans are inexpensive, and Bacillus subtilis fermentation has been practiced in Japan for over 1,000 years.

Western Japan (Osaka and Kyoto) has historically lower natto consumption — a cultural divide that persists. Osaka-style eating culture tends to find natto's intensity incompatible with Kansai flavor preferences.

The Nutrition

Natto is genuinely remarkable in its nutritional profile:

Nattokinase: An enzyme produced specifically by Bacillus subtilis natto fermentation. Research suggests it may have cardiovascular benefits — specifically related to fibrinolytic activity (the ability to dissolve blood clots). No other significant food source of nattokinase exists.

Vitamin K2 (MK-7): The highest dietary source of vitamin K2 in its MK-7 form. K2 is associated with calcium metabolism, bone health, and cardiovascular health. The MK-7 form has a much longer biological half-life (72 hours) compared to the K1 form in green vegetables.

Protein: 18g per 100g, complete amino acid profile.

Probiotics: The live B. subtilis culture provides probiotic benefit.

Fiber, iron, calcium: Notable quantities of each.

The nutritional research on natto is extensive and largely positive — it is one of those foods where the reputation as a health food tracks with evidence rather than folk tradition alone.

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Natto requires an acquired taste, and the acquisition requires repeated exposure. The first experience is challenging. The fifth or sixth is different. By the time natto appears regularly on your breakfast table, the smell has stopped registering as negative and the sticky umami depth is simply what breakfast tastes like. This is how most Japanese people experience it — not as something extreme, but as unremarkable daily food. The extremeness is in the first encounter, not the hundredth.