Human Studies on the Health Benefits of Natto

Natto is a traditional Japanese fermented soybean food produced by Bacillus subtilis var. natto. Several human epidemiological and clinical studies suggest potential benefits for cardiovascular health, bone health, and metabolic function.

1. Natto and Cardiovascular Disease Risk

Reference
Blekkenhorst et al. 2020 natto vitamin K2 cardiovascular mortality study
Journal: Journal of Nutrition

Study Design

• Population study

• Participants: ~4,800 adults

• Age: ≥55 years

• Location: Netherlands (Rotterdam Study)

• Researchers examined intake of vitamin K2 (menaquinones) from fermented foods like natto.

Key Results

Higher intake of vitamin K2 (common in natto) was associated with:

• ↓ Coronary heart disease risk

• ↓ Cardiovascular mortality

• ↓ Arterial calcification

Mechanism

Vitamin K2 activates proteins such as matrix Gla protein, which help prevent calcium deposition in arteries.

2. Natto and Bone Health

Reference
Ikeda et al. 2006 natto intake hip fracture risk Japanese women study
Journal: Journal of Nutrition

Study Design

• Population cohort study

• Participants: ~944 Japanese women

• Age: elderly women

• Duration: follow-up over several years

Key Results

Women who consumed natto more frequently had:

• Higher bone mineral density

• Lower risk of hip fracture

Proposed Reason

Natto is one of the richest dietary sources of:

• Vitamin K2 (menaquinone-7)

Vitamin K2 helps activate osteocalcin, which supports bone mineralization.

3. Natto and Blood Clot Prevention

Reference
Hsia et al. 2009 nattokinase fibrinolytic human study

Study Design

• Human intervention study

• Participants consumed nattokinase (enzyme from natto).

Key Findings

After supplementation:

• Increased fibrinolytic activity

• Reduced blood clot formation markers

• Improved blood flow parameters

Mechanism

Nattokinase may:

• degrade fibrin (clot protein)

• enhance natural clot-dissolving pathways.

4. Natto and Blood Pressure

Reference
Kim et al. 2008 nattokinase blood pressure randomized trial
Journal: Hypertension Research

Study Design

• Randomized, double-blind, placebo-controlled trial

• Participants: adults with borderline hypertension

• Duration: 8 weeks

Results

Nattokinase group showed:

• ↓ Systolic blood pressure (~5–6 mmHg)

• ↓ Diastolic blood pressure (~2–3 mmHg)

Major Bioactive Compounds in Natto

Simple Take-Home Message

Human studies suggest natto consumption may:

✔ improve cardiovascular health
✔ reduce arterial calcification
✔ support bone density
✔ lower blood pressure
✔ enhance fibrinolysis (blood clot breakdown)