What Exactly Is Natto?

Natto is a traditional Japanese fermented food made from whole soybeans inoculated with Bacillus subtilis bacteria. After roughly 24 hours of fermentation at about 40°C (104°F) under carefully controlled conditions, the soybeans develop a sticky, stringy coating and a pungent smell that's hard to forget. The stickiness comes from polyglutamic acid produced during fermentation, and the sharp aroma is caused by ammonia compounds. It's an experience for all the senses.

Natto's history stretches back over 1,000 years to the Heian period (794–1185 AD). According to popular folklore, boiled soybeans were accidentally wrapped in rice straw, where naturally occurring Bacillus subtilis kicked off fermentation. Ibaraki Prefecture, and especially Mito City, is widely considered natto's cultural heartland and rumored birthplace.

Here's something worth knowing right away: natto is polarizing. Even in Japan, surveys show that 15–18% of people dislike it. So if you've tried natto and struggled, you're in very good company. Stick with us, because there are ways to make it work.

Why Is Everyone Suddenly Talking About Natto?

Fermented foods have been on a steady rise in Western kitchens for years. Kimchi, kombucha, kefir: they've all had their moment. Natto is the next frontier, sometimes called the "final boss" of the fermented food trend. It's the one that truly tests your commitment.

The momentum is real. The Japan Natto Cooperative Society Federation expanded its multilingual "Natto Power" global campaign in 2026, branding natto as a "Japanese Power Food" and actively introducing it to Western audiences. The global natto market, valued at roughly $1.36 billion in 2024, is projected to reach $2.05 billion by 2031, growing at about 6% per year.

Why the fascination? Japan has the world's second-highest life expectancy at 84.8 years, and natto is a daily dietary staple for millions. The average Japanese person eats around 41 packs of natto per year, roughly 1.5 packs per week. When a country with that kind of longevity eats something that consistently, people pay attention. Natto is a culturally authentic food worth exploring right now.

The Nutritional Case for Natto

Start with the headline nutrient: Vitamin K2. Natto is the richest known dietary source of Vitamin K2 (menaquinone), accounting for a remarkable 87.5% of all fermented food-derived K2 intake in a study of Japanese adults. K2 plays a critical role in calcium metabolism, directing calcium into bones and teeth rather than arteries. Most Americans are significantly deficient in K2 because the Western diet simply doesn't include enough fermented foods that contain it. Natto fills that gap like nothing else.

The protein profile is equally impressive. Natto delivers approximately 17.7–19g of protein per 100g and contains all essential amino acids, making it a rare complete plant-based protein that sets it apart from most other legumes. Per 100g, you're also getting about 212 calories, 11g of fat, 5.4g of dietary fiber, 217mg of calcium, and 8.6mg of iron (48% of your daily value).

Then there's nattokinase, an enzyme produced during fermentation. Nattokinase has been studied for its ability to break down fibrin, a protein involved in blood clot formation, and for its potential to support cardiovascular health. The Takayama Study, which followed 29,079 Japanese adults over 16 years, found that those in the highest quartile of natto intake had a 25% lower risk of cardiovascular disease mortality and a 32% lower risk of stroke mortality compared to those who ate the least. Japan's National Cancer Center also reported in 2020 that high natto consumption is associated with lower overall mortality risk.

It's worth noting that the nattokinase supplement market is booming (valued at $38.9 million in 2024), but whole-food natto delivers a more complete nutritional package: the K2, the protein, the fiber, the probiotics, and the nattokinase all together. Supplements capture one piece; the food captures the whole picture.

A Beginner's Guide to Eating Natto Without Giving Up

First, let's talk about what you'll find in the package. A standard serving of natto comes in a small styrofoam container with a sauce packet (usually a soy-based tare) and a packet of karashi (Japanese mustard). Everything you need for your first bite is right there.

The Temperature Rule

This is important: never heat natto above 40°C (104°F). Higher temperatures destroy the live Bacillus subtilis bacteria and degrade the Vitamin K2 content. If you're adding natto to warm dishes, stir it in at the very end, after the food has cooled slightly. For beginners who want to fold it into fried rice or omelets, know that you'll get the flavor and protein but lose some of the probiotic and K2 benefits. It's a fair trade-off while you're getting used to the taste.

The Stirring Technique

Before adding any sauce, stir the natto vigorously for 40–60 seconds. This develops the glossy, stringy texture and is said to mellow the flavor. Many natto lovers consider this step non-negotiable. You'll see the strings become longer and silkier as you stir. Then add the sauce and karashi, and give it a few more gentle stirs.

Choose the Right Type

Not all natto is created equal for beginners. Start with hikiwari natto (finely chopped soybeans). It has a milder flavor and less intense texture than whole-bean varieties. Small-bean natto is the most common, large-bean natto has a bolder taste, and wara (straw-wrapped) natto is the most traditional and pungent. Save those for later.

The Beginner Progression

Don't go all-in on your first try. Start with a ratio of about 1 part natto to 4 parts other ingredients. Gradually increase the natto proportion over a few weeks as your palate adjusts. This gentle approach makes a real difference.

Beginner-Friendly Pairings

• Over steamed white rice (the classic, and still the best starting point)
• Mixed with kimchi for a double-fermented punch
• Topped with sliced avocado for creaminess that balances the texture
• Drizzled with ponzu sauce or sesame oil
• Sprinkled with chopped green onions

For intermediate eaters, try folding natto into fried rice or a soft omelet. The heat softens the intensity, making it more approachable (just remember the temperature trade-off with probiotics).

Natto pairs naturally with other Japanese pantry staples you may already have: soy sauce, karashi mustard, short-grain rice, and a bowl of miso soup on the side. Together, they make a simple, complete Japanese breakfast that's been fueling people for centuries.

Where to Buy Natto in the US and What to Look For

Finding natto in a mainstream American grocery store can be a challenge. Your best bet is a Japanese grocery store or Asian specialty market, where you'll find authentic brands with the quality and flavor that make a real difference for first-timers.

Natto is sold frozen, so plan to thaw it in the refrigerator overnight before eating. When shopping, look for packages that include the sauce and karashi packets — a sign of a traditional, ready-to-eat product.

If you don't have a Japanese grocery nearby, online ordering with proper cold shipping makes natto accessible anywhere in the US. Here at Tomato Japanese Grocery, we carry natto and ship nationwide via UPS. With over 20 years of sourcing authentic Japanese specialty foods from our home base in Marietta, GA, we're always happy to help you find the right products, whether you're shopping in-store or online.

Give Natto a Real Chance — Your Taste Buds Will Thank You

Natto is an acquired taste, and that's completely normal. Many people who now eat it every morning hated it the first time. The key is setting yourself up for success: start with hikiwari, pair it with rice and the included sauce and karashi, and stir it well before eating.

When you eat natto, you're connecting with over 1,000 years of Japanese food tradition. That's a small, meaningful thing, and it's worth a little patience.

Approach it with curiosity rather than pressure. Give yourself a few tries over a couple of weeks instead of making one dramatic first attempt. You might be surprised how quickly the flavor grows on you.

We love helping people discover Japanese foods they've never tried before. If you're ready to give natto a shot, or if you want to explore other Japanese pantry staples, we're here for you. That's what a neighborhood Japanese grocery is for.