Nattokinase Side Effects: What You Should Know

Nattokinase, an enzyme derived from natto, a traditional Japanese fermented soybean dish, has gained traction as a natural health supplement. Celebrated for its heart health benefits and role in improving blood circulation, it’s vital to explore nattokinase's side effects for informed and safe use.

What is Nattokinase?

This enzyme, sourced from fermented soybeans, is known for its capacity to break down blood clots, which may reduce heart disease and stroke risks. However, its soybean base can be a concern for those with soy allergies.

Nattokinase and Blood Clotting

1. Decreased Blood Clotting and Increased Bleeding Risks: Nattokinase can reduce blood clotting, potentially leading to increased chances of bruising and bleeding. This effect is significantly pronounced when nattokinase is taken alongside medications that slow clotting, such as aspirin, ibuprofen, and other blood thinners. This combination can cause excessive bleeding and bruising​​​.^1,2
2. Worsening of Bleeding Disorders: Nattokinase acts like a blood thinner and might exacerbate bleeding disorders. People with such conditions should use nattokinase with caution. Additionally, those undergoing surgery should be aware that nattokinase might increase the chance of bleeding during and after the procedure.³
3. Interactions with Blood-Thinning Medications: There is a noted risk of increased bleeding when nattokinase is used in conjunction with blood-thinning drugs. For example, a case report highlighted a patient who had to undergo a repeat valve replacement surgery after replacing warfarin with nattokinase for an extended period. Another report mentioned internal bleeding leading to death in an elderly woman who took over-the-counter nattokinase for an irregular, rapid heartbeat.⁴

Common Side Effects

The consumption of nattokinase may lead to several side effects, especially when taken in inappropriate doses. These include:

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