A Glimpse into Natto's Ancient History
Natto, the Japanese fermented bean, is not a recent dietary trend but a food with roots stretching back over a millennium. While its exact origin is debated, popular legends and historical records provide insight into its early development. One tale recounts how the samurai Minamoto no Yoshiie accidentally created natto in the 11th century when cooked soybeans were stored in rice straw bags, leading to natural fermentation. This discovery of a nutritious and palatable food source helped sustain his troops. Another theory suggests that natto's origin lies in the Yayoi period (300 BC-AD 300), where soybeans, introduced from China, fermented spontaneously inside rice straw used for storage or housing. Regardless of its precise beginning, natto's journey from a rustic, fortuitous discovery to a staple food is clear.
By the Edo period (1603-1867), natto had become a common street food and a well-established part of the Japanese diet. Vendors sold it to townspeople, and it was widely prepared in homes. Traditionally, the fermentation process involved wrapping steamed soybeans in rice straw, which naturally contained the Bacillus subtilis bacteria necessary for fermentation. Modern manufacturing, while more controlled, still relies on this key bacterium, though it is now added manually to ensure consistent quality.
The Unique Sensory Experience: Taste, Texture, and Aroma
For many outside of Japan, natto is an acquired taste due to its sensory characteristics. Its flavor profile is complex, often described as earthy, nutty, and featuring a strong umami undertone. However, it is the unique texture that people find most polarizing: the sticky, slimy, and stringy substance that forms when the beans are stirred. The longer it is mixed, the more flavorful and frothy it becomes. This mucilaginous quality is caused by polyglutamic acid created during the fermentation process. The pungent, ammonia-like smell is also a major talking point, though proponents argue that the flavor is much milder than the aroma suggests. Regional tastes and eating habits vary, with some areas like Mito in Ibaraki prefecture being especially famous for their natto.
A Nutritional Powerhouse: The Health Benefits of Natto
The primary reason why Japanese continue to eat fermented beans is their impressive nutritional value and associated health benefits, which have been validated by modern science.
Here are some of the key health benefits:
- Rich in Probiotics: As a fermented food, natto is packed with beneficial bacteria that promote a healthy gut microbiome, which is crucial for digestion and immunity. The Bacillus subtilis strain aids in nutrient absorption and may help alleviate digestive issues like bloating and constipation.
- High in Vitamin K2: Natto is one of the richest food sources of Vitamin K2, a nutrient vital for bone health and cardiovascular health. It helps regulate calcium, directing it to the bones while preventing buildup in the arteries. Studies have even shown that high natto consumption can reduce the risk of cardiovascular mortality.
- Source of Nattokinase: The fermentation process creates a powerful enzyme called nattokinase. Research suggests this enzyme helps dissolve blood clots, improves blood flow, and lowers blood pressure.
- Packed with Protein and Fiber: Natto provides a high-quality, plant-based source of protein and is rich in dietary fiber. These help with satiety, digestion, and overall metabolic health.
How Natto Compares to Other Fermented Soy Products
Natto is not the only fermented soy product in Japanese cuisine, and it's helpful to understand its place among others. While all fermented soy foods offer nutritional advantages, their production, flavor, and texture differ significantly.
| Feature | Natto | Miso | Tempeh |
|---|---|---|---|
| Fermentation Agent | Bacillus subtilis | Aspergillus oryzae (Koji) + yeast | Rhizopus oligosporus |
| Form | Whole, slimy beans | Thick, savory paste | Firm cake/block |
| Texture | Sticky, stringy, gooey | Smooth and thick | Firm, chewy, crumbly |
| Flavor | Earthy, nutty, pungent, umami | Salty, savory, umami | Nutty, earthy |
| Preparation | Eaten raw (often mixed with rice) | Used as a seasoning or base for soup | Sliced and cooked (fried, baked, etc.) |
Preparing and Enjoying Natto
Though traditionally enjoyed over steamed rice for breakfast with a packet of soy sauce (tare) and mustard (karashi), natto's versatility allows for many creative culinary uses. It can be mixed with chopped green onions, raw egg, kimchi, or grated daikon radish to enhance the flavor. For those hesitant about the texture, incorporating it into other dishes can be a great starting point.
Common ways to eat natto:
- Natto Gohan: The classic preparation over a bowl of hot rice, mixed vigorously for optimal flavor and texture.
- Natto Toast: Spread on toast with Japanese mayonnaise and cheese, then baked until golden.
- Natto Udon: A refreshing, chilled noodle dish topped with natto, a soft-boiled egg, and seasonings.
- Natto-infused Dishes: Can be added to omelets, pasta, or used as a topping for tofu (hiyayakko).
Conclusion
The practice of eating fermented beans in Japan is a tradition rooted in a potent combination of history, culture, and, most importantly, health. Despite its polarizing reputation among those unfamiliar with it, natto's status as a superfood is well-earned. The discovery of its nutritional powerhouse, rich in probiotics, Vitamin K2, and nattokinase, explains its enduring appeal in a country renowned for its long life expectancy. The compelling health benefits, combined with its deeply ingrained cultural history and versatility in the kitchen, ensure that this unique, sticky bean will remain a staple of Japanese cuisine for generations to come.
Studies Show Natto Benefits Are Real
The Science Behind the Stickiness
The Fermentation Process Explained
Natto's iconic sliminess is the product of a specific fermentation process involving Bacillus subtilis. This beneficial bacterium breaks down the soybeans' proteins, creating the sticky polymer called polyglutamic acid. The characteristic gooey strings are a tell-tale sign of a quality batch. This fermentation process also enhances the beans' digestibility, making the nutrients more bioavailable than in unfermented soy products.
The Role of Nattokinase
Nattokinase, the enzyme responsible for natto's fibrinolytic (blood clot-dissolving) properties, is not present in unfermented soybeans. It is specifically produced by the Bacillus subtilis during fermentation, offering a potent natural benefit for cardiovascular health. This has led to nattokinase supplements being sold for those seeking its benefits without the unique taste of natto itself.
The Power of Vitamin K2
While Vitamin K1 is common in leafy greens, natto provides an exceptional source of the less-common but highly important Vitamin K2. Vitamin K2 plays a crucial role in regulating calcium metabolism, helping to build strong bones and preventing arterial calcification. This contribution to bone and heart health is a major driver of natto consumption, especially for older Japanese citizens.
Natto and Gut Health
The high probiotic content is central to natto's reputation as a health food. A robust gut microbiome is linked to countless health markers, from digestion to immunity. By introducing large amounts of beneficial Bacillus subtilis to the digestive system, natto supports a balanced and healthy intestinal environment, which is especially important for fending off harmful bacteria.
Natto's Place in Japanese Culture
Beyond its health benefits, natto's persistent popularity stems from its cultural role. It is a familiar, comforting breakfast staple for many Japanese families, often passed down through generations. Its affordability and nutritional density made it a reliable food source for people across different socioeconomic classes throughout history. The tradition of eating natto connects modern Japanese society with its culinary past, reinforcing a national appreciation for fermented foods.
Natto is a Cultural Icon
- Breakfast Staple: A morning meal of natto over rice, perhaps with an egg and some green onions, is a classic and common way to start the day.
- Regional Specialities: Different areas have their own versions and preferred toppings, such as adding sugar in Hokkaido or incorporating it into miso soup in the Tohoku region.
- Ubiquitous Availability: Natto is readily available in small, inexpensive packs at any supermarket or convenience store throughout Japan.
The Acquired Taste Challenge
While many Japanese love natto, not everyone does; a 2017 survey found that a significant portion of Japanese people dislike it, even as they acknowledge its health benefits. This makes the reasons for its consumption even more compelling, highlighting that for many, health and tradition outweigh personal flavor preferences. For newcomers, the best approach is to start with small portions and incorporate toppings that balance its strong flavor.
