# Natto (Fermented Soybean)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/natto-fermented-soybean
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-18
**Evidence Score:** 8 / 10
**Category:** Fermented/Probiotic
**Also Known As:** Bacillus subtilis natto, Fermented soybeans, Japanese fermented beans, Natou, Sticky beans, Stringy soybeans, Itohiki-natto

## Overview

Natto is a fermented soybean food containing nattokinase, a fibrinolytic enzyme that breaks down fibrin clots and supports [cardiovascular health](/ingredients/condition/heart-health). It provides high concentrations of vitamin K2 (menaquinone-7) which activates proteins essential for [bone mineralization](/ingredients/condition/bone-health) and calcium regulation.

## Health Benefits

- Natto is rich in [probiotic](/ingredients/condition/gut-health)s that support gut health by promoting the growth of beneficial bacteria, improving digestion and nutrient absorption. - It contains nattokinase, an enzyme that can reduce blood clotting, supporting [cardiovascular health](/ingredients/condition/heart-health). - Natto is a good source of vitamin K2, which is essential for bone health by aiding [calcium absorption](/ingredients/condition/bone-health) and reducing the risk of osteoporosis. - It may boost the [immune system](/ingredients/condition/immune-support) by enhancing the body's natural defenses against infections. - The fermentation process increases the bioavailability of nutrients, making them easier for the body to absorb. - Natto has anti-inflammatory properties that can reduce the risk of chronic diseases by inhibiting [inflammatory pathway](/ingredients/condition/inflammation)s. - It may help regulate blood pressure by promoting healthy blood vessel function.

## Mechanism of Action

Nattokinase directly cleaves fibrin and plasmin substrate, enhancing fibrinolysis and reducing blood viscosity through plasminogen activation. Vitamin K2 (MK-7) activates osteocalcin and matrix Gla protein via gamma-carboxylation, directing calcium to bones and away from arteries. Bacillus subtilis [probiotic](/ingredients/condition/gut-health)s colonize the intestinal tract, producing beneficial metabolites and competing with pathogenic bacteria.

## Clinical Summary

A 12-week randomized trial of 86 participants showed nattokinase (2000 FU daily) reduced systolic [blood pressure](/ingredients/condition/heart-health) by 5.5 mmHg compared to placebo. Studies on vitamin K2 from natto demonstrate improved [bone mineral density](/ingredients/condition/bone-health), with one 3-year trial showing 1.3% greater femoral neck density in postmenopausal women. Small-scale studies suggest nattokinase may reduce arterial stiffness, though larger cardiovascular outcome trials are needed. Evidence for [probiotic](/ingredients/condition/gut-health) effects relies primarily on observational data from Japanese populations with high natto consumption.

## Nutritional Profile

- High in protein and dietary fiber.
- Contains vitamins such as vitamin K2 and B2.
- Provides minerals like iron, calcium, and magnesium.

## Dosage & Preparation

A typical serving size of natto is 50-100 grams per day. It can be eaten on its own or added to rice and other dishes. Consult a healthcare provider before use.

## Safety & Drug Interactions

Natto is generally safe but can cause gastrointestinal upset, bloating, or allergic reactions in soy-sensitive individuals. Nattokinase may enhance anticoagulant medications like warfarin, increasing bleeding risk and requiring medical supervision. High vitamin K2 content can interfere with vitamin K antagonist medications, potentially reducing their effectiveness. Pregnant and breastfeeding women should avoid nattokinase supplements due to insufficient safety data, though traditional natto consumption appears safe.

## Scientific Research

Numerous studies, including randomized controlled trials, have explored natto's [cardiovascular](/ingredients/condition/heart-health) and [bone health](/ingredients/condition/bone-health) benefits. Meta-analyses support its role in improving gut health.

## Historical & Cultural Context

Natto has been consumed in Japan for over a thousand years, traditionally as a breakfast food. It is valued for its health benefits and distinctive flavor.

## Synergistic Combinations

miso, kimchi, kefir

## Frequently Asked Questions

### How much nattokinase is in natto?

Traditional natto contains approximately 1000-1500 fibrinolytic units (FU) per 100-gram serving. Commercial nattokinase supplements typically provide 2000-4000 FU per capsule, equivalent to 2-4 servings of natto.

### Can natto replace vitamin K2 supplements?

A 100-gram serving of natto provides 800-1000 mcg of vitamin K2 (MK-7), significantly exceeding typical supplement doses of 45-180 mcg. This makes natto one of the richest dietary sources of bioactive vitamin K2.

### Does natto interfere with blood thinners?

Yes, natto's nattokinase content can potentiate anticoagulant medications like warfarin, increasing bleeding risk. The vitamin K2 content may also counteract warfarin's effects, making INR levels unpredictable.

### How long does nattokinase stay active in the body?

Nattokinase activity peaks 2-8 hours after consumption and remains detectable for up to 24 hours. The fibrinolytic effects gradually decline, which is why daily consumption is typically recommended for sustained benefits.

### Is natto safe for people with soy allergies?

Natto may be problematic for individuals with soy allergies, as fermentation doesn't eliminate all allergenic proteins. However, some people with mild soy sensitivities tolerate fermented soy products better than unfermented forms due to protein modification during fermentation.

### What is the difference between natto and other fermented soy products like tempeh or miso?

Natto is uniquely characterized by its sticky, stringy texture and is made by fermenting whole soybeans with Bacillus subtilis bacteria, whereas tempeh uses a mold-based fermentation and miso is a fermented paste. Natto's specific fermentation process creates nattokinase, an enzyme not found in significant amounts in tempeh or miso, making it particularly valued for cardiovascular support. While all three are nutrient-dense fermented soy foods, natto has the highest concentration of nattokinase and vitamin K2, making it distinct in its health applications.

### Does cooking or heating natto destroy its nattokinase enzyme?

Yes, nattokinase is heat-sensitive and begins to denature at temperatures above 140-150°F (60-65°C), losing its enzymatic activity when exposed to high heat. To preserve nattokinase's cardiovascular benefits, natto should be consumed raw or added to dishes after cooking rather than being heated directly. This is why natto is traditionally served fresh with rice or other room-temperature foods rather than incorporated into cooked dishes.

### Can natto consumption cause any digestive side effects, especially when first starting?

Some people may experience temporary bloating, gas, or changes in digestion when first consuming natto due to its high probiotic and fiber content, as the gut microbiome adjusts to increased fermented food intake. Starting with smaller portions and gradually increasing consumption can help minimize these effects while allowing beneficial bacteria to establish. These initial digestive adjustments typically subside within a few days to a week as the body adapts to natto's probiotics and prebiotic fibers.

### What does nattokinase do for your body?

Nattokinase is a serine protease enzyme that directly breaks down fibrin, the protein mesh that forms blood clots, reducing clot burden and improving blood flow. It also activates the body's own plasminogen system, amplifying natural fibrinolysis and lowering blood viscosity. Clinical data suggest it may reduce systolic blood pressure by roughly 5–6 mmHg and may improve markers of arterial stiffness, supporting overall cardiovascular function.

### Is natto safe to eat if you take blood thinners like warfarin?

Natto poses two distinct interactions for people on warfarin: nattokinase adds fibrinolytic activity that can potentiate anticoagulation, and its exceptionally high vitamin K2 content (MK-7 persists in circulation for over 72 hours) can unpredictably alter INR levels. Because even a single serving can shift prothrombin time significantly, most clinical guidelines recommend that patients on vitamin K antagonists avoid natto entirely. Always consult your prescribing physician before introducing natto or nattokinase supplements.

### How does natto support bone health?

Natto is one of the richest dietary sources of menaquinone-7 (MK-7), a long-chain form of vitamin K2 with superior bioavailability compared to MK-4 found in animal foods. MK-7 acts as a cofactor for gamma-glutamyl carboxylase, enabling post-translational carboxylation of osteocalcin, the protein that anchors calcium into the bone matrix. A three-year randomized trial found that women supplementing with MK-7 derived from natto maintained 1.3% greater femoral neck bone mineral density versus placebo, suggesting meaningful skeletal protection.

### How much nattokinase is in natto, and do supplements provide the same benefit?

A typical 100 g serving of natto contains roughly 1,000–1,500 FU (fibrinolytic units) of nattokinase, whereas the most-studied supplemental dose is 2,000 FU per day. Supplements offer the advantage of standardized potency and absence of vitamin K2, making them suitable for patients who need fibrinolytic support without affecting anticoagulation therapy. However, whole natto delivers additional co-factors including MK-7, isoflavones, and Bacillus subtilis natto, which may produce synergistic cardiovascular and gut-health benefits not fully replicated by isolated supplements.

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*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
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