Cold hands and feet are a common, frustrating complaint, and because nattokinase is marketed heavily around circulation, it is a natural supplement to wonder about. There is genuine research here, more than for many niche nattokinase claims, but it comes with real limits worth understanding before assuming it will fix persistently cold extremities.
Key Takeaways
- A 2023 double-blind, placebo-controlled crossover study found a single 2,000 FU dose of nattokinase produced statistically significant faster skin temperature recovery in the middle finger, palm, and back of the hand after cold water immersion.[1]
- A separate clinical trial on Bacillus subtilis var. natto products in female patients with lifestyle diseases found that a 4-week course of a natto-derived supplement significantly decreased the visual analog scale score for coldness of the extremities, while an active placebo produced no significant changes.[2]
- That same trial explicitly excluded people diagnosed with Raynaud’s disease, so this research does not extend to that specific vasospasm condition.
- Raynaud’s is a nerve-driven vasospasm disorder, mechanistically distinct from the blood viscosity and microcirculation effects nattokinase is studied for, which is an important reason not to assume nattokinase will help it.
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The Research That Actually Exists
One small human trial speaks directly to cold extremities. A 2023 double-blind, placebo-controlled crossover study tested whether a single 2,000 FU dose of nattokinase affected skin temperature recovery after cold water immersion. It enrolled nine healthy men, so it establishes a measurable short-term response in a small sample rather than a benefit for people with persistently cold hands and feet. It found a statistically significant treatment effect (p < 0.05) on skin temperature recovery in the middle finger, palm, and back of the hand, consistent with improved peripheral microvascular responsiveness after a cold challenge.
The Trial That Found Less
A separate clinical trial examined Bacillus subtilis var. natto products (marketed under the ingredient name NKCP) specifically in people reporting subjective cold hands and feet as a symptom, rather than in healthy volunteers subjected to a lab cold-water test. That trial found that a 4-week course of the supplement significantly decreased the visual analog scale score for coldness of the extremities, while an active placebo produced no significant changes. Two things are worth noting about this study design: it measured subjective symptom reports rather than objective skin temperature, and it specifically excluded people diagnosed with intractable peripheral circulatory disease, including Raynaud’s disease, from enrollment.
Research note: A 2025 review notes clinical data on the risks of long-term nattokinase use, such as bleeding tendency and liver burden, are limited [5].
Why Raynaud’s Is a Different Problem
Raynaud’s phenomenon is a vasospasm disorder: the small arteries in the fingers and toes overreact to cold or stress by constricting, cutting off blood flow and causing the characteristic white-to-blue-to-red color changes. The underlying mechanism is abnormal neurovascular reactivity, oversensitive nerve signaling to the arterioles, not primarily a blood viscosity or clotting-tendency problem. Nattokinase’s studied mechanisms, fibrinolysis and, in test-tube work only, reduced blood viscosity [3], address a different physiological pathway than the nerve-driven vasospasm at the root of Raynaud’s, which is a meaningful reason the existing trial excluded Raynaud’s patients rather than testing the treatment on them.
What This Means for Ordinary Cold Hands and Feet
If your cold extremities are a general circulation complaint rather than a diagnosed vasospasm condition, the cold-water-immersion trial offers a real, if modest, physiological signal that nattokinase may support faster skin temperature recovery after cold exposure. That said, cold hands and feet have several other common causes, including low blood pressure, iron deficiency anemia, thyroid dysfunction, and simply having naturally lower baseline circulation, none of which nattokinase would be expected to address. Persistent or severe cold-extremity symptoms, especially with color changes, numbness, or pain, warrant a medical evaluation rather than a supplement trial alone.
For context, the largest and longest trial of nattokinase, in 265 healthy adults over a median of 3 years, found no effect on blood pressure or on any laboratory measure tested, so results from short single-dose experiments should not be assumed to carry over to long-term use [4].
Frequently Asked Questions
Does nattokinase help with cold hands and feet?
There is modest supporting evidence. A 2023 controlled crossover study found a single dose improved skin temperature recovery after cold water immersion. A separate trial measuring subjective symptoms found that a 4-week natto-derived supplement significantly decreased coldness scores in female patients with lifestyle diseases, while an active placebo produced no significant changes.
Can nattokinase treat Raynaud’s disease?
This has not been tested. Raynaud’s is a nerve-driven vasospasm disorder, mechanistically different from the blood viscosity and fibrinolysis pathways nattokinase is studied for, and at least one relevant clinical trial specifically excluded Raynaud’s patients from enrollment.
What other causes of cold hands and feet should I rule out first?
Low blood pressure, iron deficiency anemia, and thyroid dysfunction are all common causes of cold extremities that a supplement targeting blood viscosity would not address. Persistent symptoms are worth discussing with a doctor.
How much nattokinase was used in the cold-water immersion study?
A single 2,000 FU dose was used in that double-blind, placebo-controlled crossover trial, which found statistically significant improvement in skin temperature recovery at several hand sites after cold water immersion.
These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease. Always talk to your doctor before starting nattokinase, especially if you take blood thinners or have an upcoming surgery.
References
- A single dose of oral nattokinase accelerates skin temperature recovery after cold water immersion: A double-blind, placebo-controlled crossover study. Heliyon (2023). PMID 37483751
- Effects of Bacillus subtilis var. natto products on symptoms caused by blood flow disturbance in female patients with lifestyle diseases. International Journal of General Medicine (2015). PMID 25653551
- Eszter Pais et al. Effects of nattokinase, a pro-fibrinolytic enzyme, on red blood cell aggregation and whole blood viscosity. PubMed (2006). PMID 16899918
- Hodis HN et al. Nattokinase atherothrombotic prevention study: A randomized controlled trial. Clinical hemorheology and microcirculation (2021). PMID 33843667
- Maria-Zinaida Dobre et al. Navigating the Effects of Anti-Atherosclerotic Supplements and Acknowledging Associated Bleeding Risks. International Journal of Molecular Sciences (2025). PMID 41155474
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
