What is Japanese Natto?
Natto is a traditional Japanese food made by fermenting cooked soybeans with a specific strain of bacteria, Bacillus subtilis var. natto. Known for its sticky, slimy texture and pungent aroma, it is a staple breakfast food in many parts of Japan, often served over rice with soy sauce, mustard, and green onions. The unique fermentation process not only develops its distinctive characteristics but also significantly enhances its nutritional profile and bioavailability, making its nutrients easier for the body to absorb.
The Health Benefits of Natto
From its high protein content to its rich probiotic profile, natto offers a wide array of health-promoting properties that have attracted global attention.
Promotes Excellent Gut Health
As a fermented food, natto is a powerhouse of probiotics, which are beneficial living bacteria that support a healthy gut microbiome. A balanced gut flora is crucial for overall wellness, from aiding digestion to strengthening the immune system.
Key benefits for gut health include:
- Improved Digestion: Probiotics in natto help break down complex nutrients, easing digestive processes and reducing issues like bloating and constipation.
- Balanced Microbiota: The beneficial bacteria help control the balance of microorganisms in the gut, protecting against harmful pathogens.
- Prebiotic Properties: Natto is also rich in dietary fiber, which acts as a prebiotic, feeding the good bacteria in your intestines and promoting their growth.
Supports Strong Bones
Natto is an exceptional, and rare, plant-based source of vitamin K2, a fat-soluble vitamin essential for bone health.
- Activates Bone-Building Proteins: Vitamin K2 activates proteins like osteocalcin, which helps bind calcium to the bone matrix, improving bone mineral density.
- Reduces Fracture Risk: Studies have linked regular natto consumption to higher bone mineral density and a lower risk of fractures, especially in postmenopausal women.
Boosts Cardiovascular Health
One of the most researched benefits of natto is its positive impact on heart health, primarily due to the unique enzyme called nattokinase.
- Dissolves Blood Clots: Nattokinase has potent fibrinolytic activity, meaning it helps dissolve fibrin, a protein that forms blood clots. This action can improve blood flow and reduce the risk of serious cardiovascular events like heart attacks and strokes.
- Lowers Blood Pressure: Research has shown that nattokinase supplementation can lead to a significant reduction in both systolic and diastolic blood pressure.
- Maintains Supple Arteries: The high vitamin K2 content helps prevent arterial calcification by directing calcium away from arteries and into bones.
Reinforces the Immune System
A healthy gut microbiome is closely linked to a robust immune response, and natto's probiotic content supports this connection. It also contains other immune-supporting nutrients, including vitamin C, zinc, and iron. Bacillus subtilis has even been shown to reduce the risk of respiratory infections.
Comparison: Natto vs. Other Fermented Soy Products
Natto's fermentation process and nutritional profile differ from other popular fermented soy products. The following table highlights some key distinctions.
| Feature | Natto | Tempeh | Miso |
|---|---|---|---|
| Texture | Distinctively sticky, slimy, and stringy. | Firm, dense, and nutty. | Paste-like, smooth or chunky. |
| Flavor | Pungent, savory, and nutty, often described as an acquired taste. | Earthy, mushroom-like flavor. | Salty, savory (umami), and can be sweet or pungent depending on the type. |
| Probiotic Content | Very high due to active Bacillus subtilis. | Contains live cultures, but less concentrated than natto. | Often pasteurized, which can kill active probiotics. |
| Nattokinase | Rich, naturally occurring source. | Not present. | Not present. |
| Vitamin K2 | Exceptionally high concentration. | Moderate levels. | Moderate levels. |
Are There Any Risks or Side Effects?
While natto is safe for most people, certain individuals should be cautious due to its powerful effects.
- Drug Interactions: Individuals on blood-thinning medications (e.g., warfarin) should consult a doctor before consuming natto, as its high vitamin K2 content and nattokinase enzyme can interfere with the medication's effectiveness.
- Soy Allergies: As natto is a soybean product, anyone with a soy allergy should avoid it.
- Hypothyroidism: Soy is a goitrogen, which may interfere with thyroid function in people with an existing thyroid condition. Those with hypothyroidism may want to limit their intake.
- Digestive Discomfort: Some people new to fermented foods may experience temporary bloating or gas.
How to Enjoy Natto
If the unique flavor and texture are a barrier, there are many ways to make natto more palatable. The traditional method involves mixing it vigorously with chopsticks to create a frothy texture before adding condiments like soy sauce, mustard (karashi), and chopped green onions. For those still adjusting, consider these methods:
- On Toast: Spread natto on toast with Japanese mayonnaise and cheese, then broil for a savory, less pungent experience.
- With Other Flavors: Mix it into dishes with other strong flavors, such as curries or ramen.
- In Blends: Blend natto into a dip with tofu, umeboshi (pickled plum), and grated ginger to mellow its intensity.
- Freeze-Dried or Powdered: Freeze-dried or powdered natto offers the benefits without the slimy texture and strong odor, and can be added to salads, yogurt, or smoothies.
For more detailed research on the therapeutic potential of natto and its bioactive compounds, the study in Biochemical Research International offers an excellent overview.
Conclusion
Ultimately, is Japanese natto good for you? Yes, its dense nutritional profile and unique bioactive compounds—especially the probiotics, vitamin K2, and nattokinase—offer significant health benefits for digestion, bone density, and cardiovascular health. While its taste and texture are an acquired taste for some, the versatility of this fermented superfood means it can be incorporated into a wide variety of diets. As with any dietary change, those with pre-existing conditions or on certain medications should consult a doctor before adding it regularly to their regimen. However, for most, natto presents a powerful and healthy addition to a balanced diet.
