Natto Guide: What It Is, How It Tastes, and How to Eat It

Natto (納豆) is fermented soybeans, produced by inoculating cooked soybeans with Bacillus subtilis var. natto and fermenting them at 40°C for about 24 hours. The result: dark, sticky soybeans coated in a web of white strings, with a sharp, ammonia-adjacent smell and a flavor that's deeply savory, slightly bitter, and intensely umami.

It's one of the most nutritious foods regularly eaten in Japan — high in protein, vitamin K2, probiotics, and a compound called nattokinase — and one of the most divisive. Many Japanese people love it; a significant number dislike it even from childhood. For non-Japanese eaters, it's often an acquired taste that takes 2-3 exposures.

This guide explains what natto actually is, what it tastes like, and how to eat it the way Japanese people do.

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What Natto Tastes Like

The honest description:

Smell: Pungent and ammonia-like, similar to very aged blue cheese or a strong brie. The smell is the most offputting part for most people.

Texture: Sticky and stringy. When you stir natto vigorously, long white protein strands form between the beans. These strings cling to chopsticks, to your mouth, and to each other. The texture is somewhere between very ripe Brie and okra.

Flavor: Once you get past the smell and texture, the taste is deeply savory — earthy, slightly nutty, with strong umami and a faint bitterness. It's less extreme than the smell suggests.

On rice: The acidity and salt of the soy sauce packets balance the bitterness. The mustard cuts through the richness. Mixed into hot rice, the flavor mellows significantly.

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How to Eat Natto

Most natto in Japan is sold in small styrofoam or cardboard packs of 3, each containing one serving. The pack includes two small packets: tare (a seasoned soy sauce) and karashi (Japanese hot mustard).

The standard preparation:

1. Open the pack and remove the paper film covering the beans.
2. Add the mustard and tare packets to the beans.
3. Stir vigorously with chopsticks — 40-50 stirs — until the mixture becomes frothy and the strings have multiplied. Stirring develops the flavor and changes the texture.
4. Spoon over a bowl of hot short-grain rice.
5. Optional: add a raw egg yolk, sliced scallions, or a drizzle of more soy sauce.

The stirring step matters. Under-stirred natto is stickier and stronger; well-stirred natto has a lighter, more integrated texture. Japanese home cooks often stir much longer than Western recipes suggest — 80-100 stirs for some people.

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Natto Additions

Egg Yolk

A raw egg yolk stirred into natto before the tare rounds the flavor significantly, adding richness that mellows the bitterness. This is one of the most common additions.

Scallions (Negi)

Sliced thin and scattered on top. The fresh sharpness of scallion cuts through the heavy fermented notes.

Kimchi

Kimchi + natto is a popular combination — the acidity and crunch of kimchi contrasts with the soft, sticky natto. Common in Japan as a side dish or mixed into ramen.

Karashi vs Mustard

The small yellow mustard packet is Japanese karashi — sharper and more pungent than yellow American mustard, closer to Chinese hot mustard. Don't substitute Dijon; the flavor profile is wrong. If you can't find karashi, wasabi or Chinese hot mustard is a closer substitute.

Natto on Toast

A growing trend in Japan — natto on sourdough toast, sometimes with mayonnaise, sometimes with cheese. The European format softens the fermented flavor into something more approachable.

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The Health Argument

Natto is genuinely nutritious:

Vitamin K2 (MK-7): Natto contains more MK-7 than almost any other food. Vitamin K2 directs calcium to bones rather than arteries and plays a role in cardiovascular health. This is why Japanese researchers have studied the correlation between natto consumption and bone density.

Nattokinase: A protease enzyme produced during fermentation that has been studied for potential blood-thinning properties. The research is promising but not definitive.

Probiotics: Live Bacillus subtilis var. natto in the beans. The spore-forming nature of this bacterium makes it more resistant to stomach acid than many other probiotics.

Protein: One 50g serving contains about 8-9g of protein, comparable to an egg.

The Japanese longevity case for natto is often cited — regions with high natto consumption (primarily eastern Japan, especially the Kanto and Tohoku regions) have lower cardiovascular mortality rates than regions where natto is rarely eaten (Osaka and western Japan). The relationship is correlational, not proven causal.

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Regional Differences

Natto is primarily a food of eastern Japan (Kanto, Tohoku, Hokkaido). In western Japan — Osaka, Kyoto, Hiroshima — natto is much less commonly eaten and many residents actively dislike it. When Japanese people say they don't eat natto, they're usually from western Japan.

Types:

• Itohiki natto (sticky natto) — the standard supermarket natto
• Hikiwari natto — broken, smaller-cut beans with less intense texture, easier starting point for beginners
• Mito natto — Ibaraki Prefecture's style, considered the gold standard; larger beans, milder flavor

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First-Timer Tips

1. Start with hikiwari (broken bean style) — smaller pieces and slightly milder texture.
2. Stir well before eating. Unstirred natto is stronger.
3. Put it on hot rice. The heat mellows the smell noticeably.
4. Add the egg yolk. The richness helps.
5. Don't smell it first. The smell is not representative of the flavor.
6. Give it three tries. Most people who now love natto disliked it on first exposure. The brain recategorizes the smell as "food" rather than "warning signal" after repeated exposure.