CardiologyPublished: October 2026Updated: October 20269 min read
Nattokinase and Circulation: What the Evidence Shows
Nattokinase is the enzyme from natto, Japan's famously stringy fermented soybean, and it has become one of the most-asked-about supplements in our Singapore clinic. Patients arrive with headlines promising that it dissolves clots and shrinks arterial plaque, often quoting a single 2022 study. The honest summary is narrower. Nattokinase has real, modest fibrinolytic activity — it breaks down fibrin, the mesh that holds clots together. But the plaque-regression claims rest on carotid ultrasound studies, the best placebo-controlled trial found no effect, and there are no coronary imaging data at all. Here is what we know so far, what we don't, and who should not be taking it.
PC
Dr. Peter Chang
Triple Board-Certified Cardiologist & Vascular Specialist
The Short Answer: What We Know About Nattokinase
Nattokinase does something real: in the laboratory it digests fibrin directly, and small human studies show rises in fibrin breakdown products after oral doses. That makes an antithrombotic effect plausible. What it has not done is show that it shrinks plaque in the arteries that matter most.
The evidence, briefly: one large but uncontrolled study reported dramatic carotid changes; the best placebo-controlled trial found no effect on atherosclerosis progression; and there are no IVUS, OCT or CT coronary angiography data showing nattokinase reduces coronary plaque, nor any trial showing it prevents heart attacks or strokes. In Singapore, where many of our patients already take aspirin, clopidogrel or a DOAC, the more pressing question is often not whether nattokinase works, but whether it is safe alongside what they already take.
The evidence, briefly: one large but uncontrolled study reported dramatic carotid changes; the best placebo-controlled trial found no effect on atherosclerosis progression; and there are no IVUS, OCT or CT coronary angiography data showing nattokinase reduces coronary plaque, nor any trial showing it prevents heart attacks or strokes. In Singapore, where many of our patients already take aspirin, clopidogrel or a DOAC, the more pressing question is often not whether nattokinase works, but whether it is safe alongside what they already take.
What Is Nattokinase and How Does It Affect Circulation?
Nattokinase is a serine protease of about 28 kDa produced by Bacillus subtilis var. natto. Beyond digesting fibrin directly, it appears to boost the body's own clot-dissolving system by raising t-PA activity and degrading PAI-1, its natural brake. It also has modest effects on platelets and on ACE, which is where the blood pressure claims come from.
The first problem is getting it into the bloodstream. An intact protein of this size should not survive digestion well, and although small studies show changes in D-dimer, fibrin degradation products and factor VIII after oral dosing, the pharmacokinetics of nattokinase remain poorly characterised. Supplements are dosed in fibrinolytic units (FU), typically 2,000 to 10,800 FU a day, but FU assays are not standardised between manufacturers. Most products also strip out the vitamin K2 that natto the food contains — a detail that matters for warfarin. Supplements on Singapore pharmacy shelves are no exception.
The first problem is getting it into the bloodstream. An intact protein of this size should not survive digestion well, and although small studies show changes in D-dimer, fibrin degradation products and factor VIII after oral dosing, the pharmacokinetics of nattokinase remain poorly characterised. Supplements are dosed in fibrinolytic units (FU), typically 2,000 to 10,800 FU a day, but FU assays are not standardised between manufacturers. Most products also strip out the vitamin K2 that natto the food contains — a detail that matters for warfarin. Supplements on Singapore pharmacy shelves are no exception.
The Nattokinase Plaque Studies: Big Numbers, Weak Designs
Two studies drive most of the enthusiasm. In Ren et al. (2017), about 76 Chinese patients with carotid plaque were randomised to nattokinase or simvastatin for 26 weeks; plaque area fell 36.6% with nattokinase versus 11.5% with the statin. It was small, compared against an active drug rather than placebo, and its blinding and imaging reproducibility are unclear.
The study patients quote most is Chen et al. (2022) in Frontiers in Cardiovascular Medicine. In about 1,062 people, 10,800 FU daily for 12 months was associated with a 22% fall in carotid intima-media thickness (IMT) and a 36% fall in plaque size from baseline; a 3,600 FU group reportedly showed no benefit. These are the figures we hear most often from Singapore patients, usually via podcasts or Substack. The problems are substantial:
The study patients quote most is Chen et al. (2022) in Frontiers in Cardiovascular Medicine. In about 1,062 people, 10,800 FU daily for 12 months was associated with a 22% fall in carotid intima-media thickness (IMT) and a 36% fall in plaque size from baseline; a 3,600 FU group reportedly showed no benefit. These are the figures we hear most often from Singapore patients, usually via podcasts or Substack. The problems are substantial:
- Single-arm before-and-after comparison, with no randomised control group
- Single centre, with ultrasound readers not blinded to timepoint
- Some participants also took vitamin K2 and aspirin, muddying attribution
- Implausibly large effects: ASTEROID, with rosuvastatin 40 mg over 24 months, achieved about 6.8% atheroma volume regression, and treated carotid IMT usually changes by hundredths of a millimetre a year
The NAPS Trial and Coronary Data: What Rigorous Studies Show
The NAPS trial (Hodis et al., Atherosclerosis 2021) is the only rigorous placebo-controlled study. It randomised 265 people, median age 65, with no clinical cardiovascular disease, to 2,000 FU daily or placebo. After a median of three years, annualised change in carotid IMT and arterial stiffness did not differ between groups.
The fair counterargument is dose: 2,000 FU is about a fifth of Chen's, but no randomised trial has ever tested a dose-response. The only trial in coronary patients, Liu et al. (2024), randomised 178 people with stable coronary disease to nattokinase, red yeast rice, both or placebo for 90 days. The combination did best on lipids and blood pressure, but it measured biomarkers only, and the lipid effect is largely explained by monacolin K in red yeast rice — which is lovastatin. We know of no IVUS, OCT or CT coronary plaque data for nattokinase, in Singapore or anywhere else.
The fair counterargument is dose: 2,000 FU is about a fifth of Chen's, but no randomised trial has ever tested a dose-response. The only trial in coronary patients, Liu et al. (2024), randomised 178 people with stable coronary disease to nattokinase, red yeast rice, both or placebo for 90 days. The combination did best on lipids and blood pressure, but it measured biomarkers only, and the lipid effect is largely explained by monacolin K in red yeast rice — which is lovastatin. We know of no IVUS, OCT or CT coronary plaque data for nattokinase, in Singapore or anywhere else.
Why Breaking Down Fibrin Shouldn't Shrink Plaque
Mechanism is where the regression story struggles most. Fibrinolysis could plausibly clear mural thrombus and fibrin incorporated into plaque, and that might register as a modest change in total plaque on ultrasound. It does nothing obvious to the lipid core, the macrophage burden or the necrotic core — the components that make plaque dangerous, as we explain in our post on plaque rupture.
Those are precisely the components that respond to LDL lowering. Intravascular ultrasound trials of statins, PCSK9 inhibitors and ezetimibe, including GLAGOV, PACMAN-AMI and HUYGENS, show genuine coronary regression and plaque stabilisation. There is also a measurement problem: carotid plaque area on B-mode ultrasound is a weak surrogate for coronary atheroma volume. A neck scan that looks better is not the same as a heart that is safer, in Singapore or anywhere else.
Those are precisely the components that respond to LDL lowering. Intravascular ultrasound trials of statins, PCSK9 inhibitors and ezetimibe, including GLAGOV, PACMAN-AMI and HUYGENS, show genuine coronary regression and plaque stabilisation. There is also a measurement problem: carotid plaque area on B-mode ultrasound is a weak surrogate for coronary atheroma volume. A neck scan that looks better is not the same as a heart that is safer, in Singapore or anywhere else.
Nattokinase Side Effects: Bleeding, Surgery and Warfarin
The safety concern with nattokinase is bleeding. There are case reports of intracerebral haemorrhage, some in patients also taking aspirin. The additive risk matters most for people already on antithrombotic therapy — which, in our Singapore practice, describes a large share of those asking about it. Product quality adds uncertainty: labelled FU content is unregulated and products vary widely, so the dose on the bottle may not be the dose in the capsule.
- Dual antiplatelet therapy after a stent: adding a fibrinolytic supplement to aspirin plus clopidogrel or ticagrelor is not something we would endorse
- DOACs or warfarin: apixaban, rivaroxaban, dabigatran and warfarin already carry bleeding risk; nattokinase adds an unquantified layer
- Cilostazol for peripheral artery disease: another antiplatelet effect stacked on top
- Warfarin specifically: natto the food, rich in vitamin K2, antagonises warfarin, while K2-free supplements may add to its effect — either way, the INR becomes unpredictable
- Procedures: stop it about 1 to 2 weeks before surgery, endovenous ablation or arterial access — a conventional window borrowed from other antithrombotic supplements, not formal data
Nattokinase vs Statins: What Actually Reverses Plaque
If the goal is less plaque and fewer heart attacks, LDL lowering is the intervention with both imaging and outcome data. High-intensity statins, ezetimibe and PCSK9 inhibitors have shown coronary regression on IVUS and fewer events across tens of thousands of patients. Nattokinase has neither, so it is not a substitute — and we would be uneasy about anyone in Singapore stopping a statin in its favour.
Many patients who reach for nattokinase are, understandably, worried about statin side effects. That conversation is worth having directly; we cover the evidence in are statins safe? For people who want a food-first approach, the measures that move LDL reliably — less saturated fat, more soluble fibre, weight loss where needed — deserve priority, and natto the food remains a perfectly reasonable part of a varied diet.
Many patients who reach for nattokinase are, understandably, worried about statin side effects. That conversation is worth having directly; we cover the evidence in are statins safe? For people who want a food-first approach, the measures that move LDL reliably — less saturated fat, more soluble fibre, weight loss where needed — deserve priority, and natto the food remains a perfectly reasonable part of a varied diet.
Taking Nattokinase in Singapore? What We Advise
If you are set on taking it, tell your doctor and pharmacist, particularly if you take any antiplatelet or anticoagulant, and stop it before any procedure. Health supplements in Singapore do not need pre-market approval from the Health Sciences Authority, so neither efficacy nor dose content is independently verified.
At our clinic at Paragon Medical Centre on Orchard Road, we would rather assess what you are actually worried about. That may mean a lipid profile and Lp(a), a coronary calcium score or CT coronary angiography, and a clear plan for LDL. A first consultation typically costs SGD 150 to SGD 350. As for nattokinase itself, an adequately powered placebo-controlled trial at around 10,000 FU with CT or IVUS endpoints would settle the question. Until then, the sceptical position is the evidence-based one.
At our clinic at Paragon Medical Centre on Orchard Road, we would rather assess what you are actually worried about. That may mean a lipid profile and Lp(a), a coronary calcium score or CT coronary angiography, and a clear plan for LDL. A first consultation typically costs SGD 150 to SGD 350. As for nattokinase itself, an adequately powered placebo-controlled trial at around 10,000 FU with CT or IVUS endpoints would settle the question. Until then, the sceptical position is the evidence-based one.
Frequently Asked Questions
Common Questions About Nattokinase and Circulation
Does nattokinase dissolve arterial plaque?
There is no good evidence that it does. The claims rest on carotid ultrasound studies, and the largest, Chen 2022, had no control group. The best placebo-controlled trial, NAPS, found no difference in carotid wall thickness or stiffness after three years. Nattokinase breaks down fibrin, but plaque is mainly cholesterol, inflammatory cells and necrotic tissue, which fibrin breakdown does not address.
Is it safe to take nattokinase with aspirin or blood thinners?
We advise against it. Nattokinase has fibrinolytic activity, and there are case reports of brain haemorrhage, some in people also taking aspirin. Combined with dual antiplatelet therapy, a DOAC, warfarin or cilostazol, it adds bleeding risk that nobody has properly quantified. If you take any of these, discuss it with your cardiologist before starting.
Can nattokinase replace my statin?
No. Statins, ezetimibe and PCSK9 inhibitors have shown coronary plaque regression on intravascular ultrasound and fewer heart attacks and strokes in large trials. Nattokinase has no coronary imaging data and no outcome data. If statin side effects are the real concern, that is worth addressing directly, because there are usually workable alternatives.
How long before surgery should I stop nattokinase?
We generally suggest stopping it about one to two weeks before any surgery or procedure, including varicose vein ablation, angiography or arterial access. There are no formal data for nattokinase; this window is borrowed from other supplements with antithrombotic effects. Always list it on your pre-operative medication form, alongside fish oil, ginkgo and similar products.
Is nattokinase regulated in Singapore?
Not in the way medicines are. Health supplements in Singapore do not need pre-market approval from the Health Sciences Authority, and fibrinolytic unit assays are not standardised between manufacturers. That means the dose on the label may not match what is in the capsule, and products vary widely in quality.
Should I take nattokinase for circulation in Singapore?
For most people, we would not recommend it. It may modestly enhance clot breakdown, but no trial has shown better circulation, fewer clots or fewer strokes. If you have leg symptoms, vascular disease or worries about plaque, a specialist assessment in Singapore, with targeted tests and proper LDL management, will do far more than a supplement.