Natto: A K2 Powerhouse
Natto, a traditional Japanese food made from fermented soybeans, is widely recognized as a superfood due to its unique nutritional profile. While fermented foods are beneficial for gut health, natto stands out for its extraordinarily high concentration of menaquinone-7 (MK-7), a potent form of vitamin K2. The fermentation process, led by the Bacillus subtilis bacteria, is responsible for this powerful conversion, transforming the soybeans into a sticky, pungent, and incredibly nutritious product.
The K2 Content in a Tablespoon
The short and definitive answer to how much K2 is in a tablespoon of natto is over 150 micrograms (mcg). This single spoonful provides more than twice the typical recommended daily intake for healthy adults. Most of the vitamin K2 in natto is in the form of menaquinone-7 (MK-7), which has a longer half-life and is more bioavailable than the MK-4 form found in animal products like meat and eggs.
Comparing K2 Sources: Natto vs. Other Foods
While other fermented foods and animal products contain K2, none come close to the concentration found in natto. Here's a comparison to illustrate the difference:
| Food Source | Form of K2 | Approximate K2 Content | Context |
|---|---|---|---|
| Natto | Primarily MK-7 | 150+ mcg per tbsp | Richest and most potent source |
| Gouda Cheese | Primarily MK-9 | 32 mcg per 50g | A decent source, but much lower concentration |
| Chicken Liver | Primarily MK-4 | 12.6 mcg per 100g | Good animal-based source, but significantly less potent than natto |
| Egg Yolk (from grass-fed chickens) | Primarily MK-4 | 15.5 mcg per yolk | Small amounts compared to natto |
| Sauerkraut | Mixed Menaquinones | 4.8 mcg per 100g | Fermented vegetable source, but very low concentration |
This table clearly shows natto's unmatched position as the top dietary source of vitamin K2. While consuming a variety of K2-rich foods is beneficial, a single tablespoon of natto provides a powerful and convenient way to meet and exceed daily needs, particularly for the crucial MK-7 variant.
The Health Benefits of Natto's K2
The high concentration of vitamin K2 in natto contributes to several significant health benefits. The primary function of vitamin K2 is its role in calcium metabolism, which impacts both skeletal and cardiovascular health.
Bone Health: Vitamin K2 activates osteocalcin, a protein that binds calcium and integrates it into the bone matrix, improving bone mineral density. Research has shown that adequate vitamin K2 intake reduces the risk of fractures and slows age-related bone density loss, especially in postmenopausal women.
Cardiovascular Health: K2 activates another protein, matrix Gla protein (MGP), which helps prevent calcium from depositing in soft tissues like the arteries. This action helps prevent arterial calcification, a major risk factor for heart disease. A single serving of natto can make a meaningful contribution to preventing this process.
Other Key Nutrients in Natto: Beyond its impressive K2 content, natto provides a host of other beneficial compounds, which work synergistically with K2 to promote health:
- Nattokinase: An enzyme produced during fermentation that has powerful fibrinolytic properties, meaning it helps dissolve blood clots. This makes natto particularly beneficial for heart health.
- Probiotics: The Bacillus subtilis bacteria are powerful probiotics that support gut health, aid digestion, and boost the immune system.
- Soy Isoflavones: These plant compounds have been linked to a lower risk of certain cancers and improved heart health.
- Protein and Fiber: As a soybean product, natto is an excellent source of plant-based protein and dietary fiber, supporting satiety and digestive regularity.
Potential Considerations
While highly beneficial, some people may need to exercise caution with natto. The high vitamin K content can interact with certain medications, such as blood thinners like warfarin. Individuals on such medication should consult their doctor before adding natto to their diet. However, the MK-7 in natto can also provide more stable blood clotting factor levels than a high intake of K1.
Conclusion
A tablespoon of natto is one of the most potent and efficient ways to boost your intake of vitamin K2, particularly the highly effective MK-7 variant. With over 150 micrograms of K2 in a single serving, along with powerful enzymes like nattokinase and beneficial probiotics, natto offers a comprehensive boost to bone and cardiovascular health. While its pungent aroma and sticky texture can be an acquired taste, its remarkable nutritional benefits make it a worthy addition to a health-conscious diet. For those seeking a whole-food source of K2, natto is a clear winner among all dietary options.
