Nattokinase & Bleeding Risk: What You Need to Know

Key Findings

This case report documents a fatal adverse event in an elderly woman linked to nattokinase supplementation. The patient developed hemoperitoneum (blood accumulation in the peritoneal cavity) after consuming nattokinase, a soybean fermentation product marketed for potential thrombolytic effects. The authors conclude that nattokinase may contribute to severe bleeding complications, particularly in individuals with comorbidities or on anticoagulant therapy, and caution against its unregulated use.

Study Design

The study is a retrospective case report published in 2021. It analyzes a single patient’s clinical course and outcomes. No sample size or control group is provided, as the design focuses on qualitative documentation of an isolated incident. The timeframe from nattokinase initiation to hemoperitoneum onset is unspecified in the summary, but the event occurred after "several weeks" of use. Demographics include an elderly woman (age unspecified) with a history of hypertension and anticoagulant use (apixaban), though details about her overall health status or other medications are limited.

Dosage & Administration

The dose or formulation of nattokinase is not explicitly stated in the summary. However, the supplement was reportedly taken orally, likely in capsule form, as is standard for commercial nattokinase products. Duration of use prior to the adverse event was "several weeks," but exact daily dosage or total exposure time remains unclear.

Results & Efficacy

The study does not evaluate efficacy, as it focuses on an adverse outcome. Hemoperitoneum was confirmed via imaging and surgical findings, with no identifiable traumatic or structural cause (e.g., organ rupture). Laboratory tests showed prolonged clotting times, suggesting impaired hemostasis. The patient died despite medical intervention. No statistical analysis (e.g., p-values, confidence intervals) is applicable in this single-case report.

Limitations

1. Case report design: Causality between nattokinase and hemoperitoneum cannot be definitively established due to the lack of a control group or systematic data collection.
2. Confounding factors: The patient was on apixaban, a direct oral anticoagulant, which independently increases bleeding risk. The interaction between nattokinase and anticoagulants is plausible but not proven here.
3. Missing data: Dosage, duration of supplementation, and baseline coagulation status (e.g., INR, platelet count) are not reported, limiting reproducibility and risk assessment.
4. Publication bias: The report highlights a severe outcome, potentially skewing perceptions of nattokinase’s safety profile without context from larger cohorts.
   Future research should investigate dose-dependent effects, interactions with anticoagulants, and bleeding risks in controlled trials.

Clinical Relevance

This case raises concerns about nattokinase’s safety, particularly in elderly individuals or those on anticoagulant/antiplatelet therapy. While nattokinase’s thrombolytic properties are theorized to mimic plasmin activity, this report underscores the potential for life-threatening bleeding without robust clinical oversight. Supplement users should be aware of the lack of regulatory standardization for herbal products and consult healthcare providers before use. However, given the study’s anecdotal nature, broader conclusions about nattokinase’s risk profile require validation in larger, prospective studies.

Takeaway: This report highlights a possible association between nattokinase and severe bleeding but does not prove causation. Caution is warranted, especially in vulnerable populations.