Can Nattokinase Cause Heart Palpitations?

If you've noticed your heart fluttering after starting nattokinase, you're right to pay attention — but the evidence points somewhere more reassuring than you might expect.

Heart palpitations are extremely common — one study found that 16% of people had visited their primary care provider about them — yet they are not a recognized side effect of nattokinase. A 2023 meta-analysis of 6 randomized trials and 546 participants reported no notable adverse events. This guide covers what the research actually shows, the rare indirect routes worth knowing, and when a fluttering heartbeat means it's time to call a doctor.

Table of Contents

• 1. What Heart Palpitations Actually Are
• 2. Is Nattokinase a Known Cause of Palpitations?
• 3. Could Nattokinase Indirectly Affect Your Heartbeat?
• 4. Allergic Reactions and Blood-Thinner Interactions
• 5. Common Causes to Rule Out First
• 6. When Palpitations Mean You Should See a Doctor
• 7. Formulation Quality When You're Watching for Side Effects
• 8. Frequently Asked Questions
• 9. Conclusion

1. What Heart Palpitations Actually Are

A palpitation is an increased awareness of your own heartbeat — a pounding, fluttering, racing, or skipped-beat sensation felt in the chest, throat, or neck. They are remarkably common: Cleveland Clinic reports that 16% of people have seen their primary care provider about palpitations, and they occur more often in women and at hormonal transition points like pregnancy and menopause.

Crucially, the American Heart Association describes palpitations as a symptom, not a diagnosis — and notes that in many cases the heart is in a completely normal rhythm even while a person feels them. Most episodes, in an otherwise healthy adult, are harmless.

This matters for anyone evaluating a supplement. Because palpitations have dozens of possible triggers and affect such a large share of the population, feeling them shortly after starting nattokinase does not, on its own, establish that the supplement caused them — a distinction that runs through the rest of this article.

2. Is Nattokinase a Known Cause of Palpitations?

The direct answer, based on current evidence, is no. A 2023 systematic review pooling six randomized controlled trials and 546 participants reported no notable adverse events from nattokinase — including a 3-year trial. The professional monograph on Drugs.com similarly notes that small, short-term trials reported no adverse reactions.

Real-world surveillance points the same way. An analysis of FDA adverse-event data covering roughly 147,874 records found no reports of palpitations linked to nattokinase. That is observational data, and absence of reports is not the same as proof of safety — but across both controlled trials and post-market records, palpitations simply do not appear as a signal.

The side effects that are documented tend to be mild digestive symptoms, with the two meaningful safety concerns being bleeding risk (in people on blood thinners) and allergy (in people sensitive to soy). Nattokinase has also been consumed as part of the fermented food natto for centuries, and a review counted around 10 clinical trials of nattokinase or natto supporting its broad tolerability.

3. Could Nattokinase Indirectly Affect Your Heartbeat?

While there is no direct causal link, a few plausible indirect routes are worth understanding. The best-established is blood pressure: the 2023 meta-analysis found nattokinase lowered systolic pressure by about 3.45 mmHg and diastolic by about 2.32 mmHg versus placebo, an effect thought to come partly from inhibition of angiotensin-converting enzyme. For most people that shift is modest, but combined with prescription blood-pressure medication it could occasionally produce lightheadedness or a heightened awareness of the heartbeat.

Individual sensitivity is the second route. A blood-pressure change that is beneficial for one person can feel like a symptom in another, which is one reason a start-low approach — reviewed in the nattokinase dosage guide — is sensible, beginning at the standard 2,000 FU per day rather than the higher research doses.

Finally, timing coincidence is easy to mistake for cause. Many people take nattokinase alongside their morning coffee, and caffeine is one of the most common palpitation triggers — meaning a fluttering heartbeat 30 minutes after a capsule may have far more to do with the caffeine than the enzyme.

4. Allergic Reactions and Blood-Thinner Interactions

Nattokinase is produced from fermented soybeans, so allergy is a real consideration. A 2022 case report in Allergology International documented anaphylaxis triggered by nattokinase in a patient with a fermented-soybean allergy. A rapid or pounding heartbeat is a recognized feature of severe allergic reactions — so anyone with a soy allergy should avoid nattokinase entirely, and a racing heart accompanied by swelling, hives, or breathing difficulty is a medical emergency.

The second concern is bleeding. Memorial Sloan Kettering notes that nattokinase may theoretically increase bleeding risk with anticoagulant, antiplatelet, and fibrinolytic drugs, and that the vitamin K in raw natto can interfere with warfarin. A 2008 case report even described a cerebellar hemorrhage after nattokinase was combined with aspirin in a vulnerable patient.

Neither of these is about palpitations specifically, but together they are the real safety story — and the reason anyone taking blood thinners or managing a cardiovascular condition should read the details on nattokinase as a natural blood thinner and consult their physician before starting.

5. Common Causes to Rule Out First

Before attributing palpitations to any supplement, it helps to consider the far more frequent triggers. The most common culprits include:

• Caffeine, alcohol, and nicotine, which all stimulate the nervous system and can make the heartbeat feel irregular.
• Medications — including decongestants containing pseudoephedrine, plus asthma, thyroid, and hormonal treatments — which are linked to palpitations in a range of people.
• Underlying conditions such as an overactive thyroid, anemia, or electrolyte imbalance, which basic blood work can reveal.

Hormones matter too: palpitations are reported more often in women, particularly around menstruation and menopause, when shifts in estrogen can affect heart rate.

A simple habit closes the gap between guesswork and answers: keep a short palpitation diary noting the time, what you ate or drank, your caffeine intake, and your stress level. Over even one or two weeks, patterns often emerge that point to a trigger far more likely than a once-daily enzyme capsule.

6. When Palpitations Mean You Should See a Doctor

Most palpitations are benign, but some are not, and the warning signs are worth memorizing. The American Heart Association advises seeking attention when palpitations last minutes to hours, or come with chest pain, shortness of breath, dizziness, or a feeling of nearly passing out — and to call emergency services for chest discomfort or fainting.

Cleveland Clinic echoes this, noting that palpitations accompanied by dizziness or passing out can signal a serious problem. Untreated atrial fibrillation, for instance, can raise the risk of stroke, so any new or changing pattern deserves evaluation rather than dismissal.

If you take nattokinase and develop new palpitations, a reasonable step is to pause and speak with your provider — especially if you also take blood thinners or blood-pressure medication. This isn't because nattokinase is an established cause, but because palpitations always deserve context, and roughly 1,062 participants in one clinical study underscore that even well-tolerated supplements are best used under informed guidance.

7. Formulation Quality When You're Watching for Side Effects

If you're monitoring how your body responds to a supplement, the formulation itself should be one thing you don't have to second-guess. BioAbsorb Nattokinase Enzyme delivers 100 mg — standardized to 2,000 FU — per capsule, matching the standard clinically studied dose of 2,000 FU, so you can start at a researched level rather than an arbitrary one.

Two design choices are directly relevant here. The enzyme is delivered in DRcaps delayed-release veggie capsules that protect it through stomach acid without the phthalates and plasticizers found in some enteric coatings, and it is intentionally free of vitamin K2 — a meaningful detail given that the vitamin K in raw natto is exactly what can interfere with warfarin. It is also non-GMO, 100% vegetarian, and free of gluten, nuts, eggs, dairy, fish, and shellfish; note, however, that because it is derived from fermented soy, it is not suitable for anyone with a soy allergy.

Every batch is third-party tested for potency, heavy metals, and microbial contaminants and manufactured in a Canadian GMP-certified facility. At [PRICE NEEDED] for a 60-day supply — [COST-PER-DAY NEEDED] per day — it's built to be a simple, single daily capsule you can trust while you pay attention to how you feel.

8. Frequently Asked Questions

Are heart palpitations a common side effect of nattokinase?

No. Palpitations were not reported in the 2023 meta-analysis of 546 participants, and a review of roughly 147,000 FDA adverse-event records found no cases linked to the supplement. If you experience them, other causes are statistically far more likely.

Could nattokinase's blood-pressure effect cause palpitations?

It's plausible but not proven. The average drop is modest — about 3.45 mmHg systolic and 2.32 mmHg diastolic — but combined with prescription blood-pressure medication, the added lowering could cause lightheadedness in sensitive individuals, so involve your physician.

Who should avoid nattokinase?

Anyone with a soy allergy, anyone taking blood thinners or antiplatelet drugs without physician oversight, and anyone scheduled for surgery or with a bleeding disorder or history of hemorrhagic stroke. Memorial Sloan Kettering flags a theoretical increase in bleeding risk in these situations.

If I feel palpitations after taking it, what should I do?

First consider common triggers like caffeine or stress and note the pattern. If the palpitations last minutes to hours, or come with chest pain, dizziness, or fainting, seek medical attention promptly.

Is nattokinase safe to take long-term?

The evidence is reassuring but still limited. A 3-year randomized trial reported no notable adverse events, and short-term trials found no adverse reactions, but large outcome trials are still lacking, so ongoing use is best guided by a healthcare provider.

Does eating natto cause palpitations?

There's no evidence that the fermented food natto causes palpitations. Its main interaction concern is its high vitamin K content, which can reduce the effect of warfarin — a reason supplement forms like BioAbsorb's are made K2-free.

9. Conclusion

Heart palpitations are common and rarely connected to nattokinase — the 2023 meta-analysis of 546 participants found no notable adverse events — but they always deserve attention, and anyone on blood thinners or blood-pressure medication should involve a physician before starting. If you choose to supplement, a clinically dosed, third-party-tested option like BioAbsorb Nattokinase Enzyme removes the formulation guesswork so you can focus on how your body actually responds.

Research References

1. Nattokinase Supplementation and Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Reviews in Cardiovascular Medicine, Vol. 24, Issue 8 (2023). Pooled six RCTs (546 participants), found significant reductions in systolic (−3.45 mmHg) and diastolic (−2.32 mmHg) blood pressure and no notable adverse events.
2. Anaphylaxis from nattokinase in a patient with fermented soybean (natto) allergy. Allergology International, Vol. 71 (2022). Documented a case of anaphylaxis to nattokinase in a soy-allergic patient, supporting the allergy caution.
3. Cerebellar hemorrhage provoked by combined use of nattokinase and aspirin in a patient with cerebral microbleeds. Internal Medicine, Vol. 47 (2008). Case report illustrating additive bleeding risk when nattokinase is combined with antiplatelet therapy.
4. Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases. Biomarker Insights, Vol. 13 (2018). Review of nattokinase's pharmacologic effects, including antihypertensive action via ACE inhibition and its clinical trial base.
5. Effective management of atherosclerosis progress and hyperlipidemia with nattokinase: A clinical study with 1,062 participants. Frontiers in Cardiovascular Medicine, Vol. 9 (2022). Large clinical study informing dose and tolerability discussion.
6. Heart Palpitations. Cleveland Clinic (2022). Overview of palpitation prevalence, triggers, and warning signs.
7. How serious are heart palpitations? Causes, symptoms and when to worry. American Heart Association (2026). Expert guidance distinguishing benign palpitations from those requiring medical attention.
8. When to Go to the Doctor for Heart Palpitations. UnityPoint Health (2026). Cardiologist overview of common triggers including caffeine, medications, and hormones.
9. Nattokinase — Integrative Medicine, Herbs. Memorial Sloan Kettering Cancer Center. Authoritative summary of bleeding-related drug interactions and the vitamin K/warfarin consideration.
10. Nattokinase: Natural Product Information. Drugs.com. Professional monograph noting trial tolerability and theoretical bleeding risk.
11. Could Nattokinase cause Heart palpitations? — a phase IV analysis. eHealthMe. Observational review of FDA adverse-event data finding no reported palpitation cases linked to nattokinase.

About the Author

David Kimbell is a health writer, digital entrepreneur and former aerospace engineer, based in Ottawa, Canada. He loves translating complex science into clear, actionable guidance for consumers seeking evidence-based solutions.

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Important Disclaimers

Medical Disclaimer: This article provides educational information only and is not intended as medical advice. Always consult with a qualified healthcare provider before starting any new supplement, especially if you have existing health conditions, take medications, or are pregnant or nursing.

FDA/Health Canada Statement: These statements have not been evaluated by the Food and Drug Administration or Health Canada. This product is not intended to diagnose, treat, cure, or prevent any disease.