Natto is a centuries-old Japanese staple made by fermenting whole soybeans with the bacterium Bacillus subtilis var. natto. The fermentation process transforms ordinary soybeans into a nutrient-dense superfood with a sticky texture and pungent flavor. It is uniquely rich in nattokinase — an enzyme not found in significant amounts in any other food — as well as one of the most bioavailable forms of vitamin K2 known.

Nattokinase works by helping the body break down fibrin, the protein that forms blood clots, supporting healthy circulation and reducing the risk of dangerous clots. Vitamin K2 (MK-7) directs calcium away from arteries and into bones, supporting both heart health and bone strength at the same time. The Bacillus subtilis bacteria in natto also acts as a probiotic, supporting gut health and immune balance.

Eating whole natto (typically 40–100g per day) provides the full combination of nattokinase, K2, probiotics, and spermidine together. Isolated nattokinase capsules (typically 100–200mg or 2,000–4,000 FU) are used by people who want the cardiovascular enzyme without the K2 — important for those on blood thinners. MK-7 supplements derived from natto are widely available for bone and cardiovascular support. Natto powder is a middle-ground option for adding to smoothies or foods.

• Heart disease and cardiovascular health
• Blood clots and poor circulation
• High blood pressure
• Osteoporosis and bone loss
• Gut health and digestion
• High cholesterol
• Inflammation
• Immune support
• Healthy aging and longevity

• Arterial calcification — MK-7 from natto activates proteins that direct calcium away from artery walls, reducing arterial stiffness over time
• Osteoporotic fractures — long-term MK-7 supplementation has reduced fracture risk in clinical trials of postmenopausal women
• Deep vein thrombosis (DVT) — nattokinase supports healthy fibrin breakdown and blood flow, reducing clot formation risk in at-risk individuals
• Stroke — population data from Japan associates regular natto consumption with meaningfully lower stroke mortality

• Natto (whole fermented soybeans) — The original and only significant whole-food source of nattokinase and high-concentration MK-7. A single 100g serving provides roughly 1,000+ mcg of MK-7 — far more than any other food.
• Hard aged cheeses (Gouda, Brie, Munster) — Among the best non-natto sources of vitamin K2 (MK-7 and MK-4), supporting arterial and bone health. Gouda is particularly rich compared to most other cheeses.
• Chicken liver and organ meats — A meaningful source of vitamin K2 (mostly MK-4 form) as well as other nutrients that overlap with natto's benefits including PQQ precursors and B vitamins.
• Tempeh — Another fermented soybean food with probiotic activity and isoflavones, providing some of natto's gut and anti-inflammatory benefits, though it lacks significant nattokinase.
• Miso — Traditional Japanese fermented soy paste with probiotic cultures and isoflavones. Shares natto's gut-supportive and inflammation-calming properties, though with minimal K2 or nattokinase.

• Digestive discomfort or bloating in people sensitive to fermented or soy-based foods
• Strong smell and sticky texture that some people find unpleasant (not a health risk, but a common barrier)
• Possible soy-related hormonal concerns in people with estrogen-sensitive conditions — evidence is mixed, consult a healthcare provider
• Increased bleeding risk if nattokinase is combined with blood-thinning medications
• Rare allergic reactions in individuals with soy allergy

• Recommended daily: Whole food: 40–100g of natto per day (1–2 traditional servings). Nattokinase supplement: 100–200mg (2,000–4,000 FU) per day. MK-7 supplement derived from natto: 90–200mcg per day.
• Best time of day: Traditionally eaten at breakfast in Japan. Nattokinase supplements are often taken in the evening since clotting activity tends to be higher at night. MK-7 supplements are best taken with the main meal.
• With or without food: Whole natto is eaten as a meal component, typically over rice. Nattokinase supplements may be taken with or without food. MK-7 should be taken with a fat-containing meal to improve absorption (it is fat-soluble).
• Time to effect: Circulatory and clotting effects of nattokinase: days to 2 weeks. Blood pressure effects: 4–8 weeks of consistent use. Bone density improvements with MK-7: 6–12 months of daily use.
• How long to take it: Natto is safe for lifelong daily consumption as a traditional food. Nattokinase and MK-7 supplements are generally used continuously for chronic conditions like cardiovascular support or bone maintenance — no need to cycle unless directed by a healthcare provider.