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claimed potency
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Most Nattokinase Supplements Don't Work
Nattokinase has strong clinical research behind it. But research means nothing if the capsule you swallow doesn't contain what the label promises.
The supplement industry in the UK has far less regulation than pharmaceuticals. Brands can print potency claims on labels without proving them. For nattokinase — a delicate enzyme sensitive to heat, moisture, and storage — this is a serious problem. Without third-party lab testing, there is no way to know what you're actually getting.
To find out which brands deliver, we purchased the 4 top-selling nattokinase supplements on Amazon UK and sent them to SORA Laboratories for independent fibrinolytic activity testing. The results were sobering.
Amazon UK Top 4: The Test Results
Each brand was tested by SORA Laboratories for actual fibrinolytic activity (FU) and compared against its label claim.
SORA Labs Independent Testing — Amazon UK Top Sellers
Source: SORA Laboratories, February 2026. Products purchased from Amazon UK.
Vinco Nattokinase
Claimed 4,000 FU per 2 capsules
Raibu Nattokinase
Claimed 2,000 FU per capsule
Hybrid Health Nattokinase
Claimed 5,000 FU per 2 capsules
Natural Foundation Supplements
Claimed 5,000 FU per capsule
How Each Brand Compared to Its Own Label
The dashed line shows 100% of the label claim. Anything left of that line means the brand failed to deliver what it promised.
Each Brand in Detail
Here's exactly what SORA Laboratories found inside each product.
Vinco Nattokinase
FailedVinco claims 4,000 FU per 2-capsule serving. The independent lab test found just 711 FU — less than a fifth of what the label promises. This is the worst result of the four brands tested. At this potency, you would need to take roughly 30 capsules per day to reach the clinically effective dose of 10,800 FU used in the largest trial.
Raibu Nattokinase
FailedRaibu claims 2,000 FU per capsule. The lab found just 528 FU — about a quarter of the promised potency. Even before testing, the low label claim of 2,000 FU per capsule is a concern: the largest clinical trial used 10,800 FU/day, meaning you'd need over 5 capsules daily just to reach the studied dose — and that's if the product delivered its full claim.
Hybrid Health Nattokinase
FailedHybrid Health claims 5,000 FU per 2-capsule serving. The lab found just 1,380 FU — barely over a quarter of the label claim. While this is the highest actual FU among the three failing brands, it still falls dramatically short of what the product promises and what clinical research suggests is needed.
Natural Foundation Supplements
PassedNatural Foundation Supplements claims 5,000 FU per capsule. The lab found over 6,720 FU — 34% more than promised. This is the only brand among the top 4 Amazon UK sellers that passed independent testing. At 5,000+ FU per single capsule, just 2 capsules daily reaches the clinically studied dose of 10,000+ FU/day.
View the Lab Certificates
Every result above comes from an official SORA Laboratories Certificate of Analysis. Click to view each one:
How to Choose a Nattokinase Supplement
Whether you buy from Amazon, Holland and Barrett, or anywhere else, here's what to look for — and what to avoid.
1. Check for FU, Not Just Milligrams
Nattokinase is measured in FU (Fibrinolytic Units) — a measure of enzyme activity, not weight. A label showing only milligrams tells you nothing about potency. The largest clinical trial used 10,800 FU/day. Look for at least 5,000 FU per capsule.
2. Demand Third-Party Lab Testing
As the results on this page show, label claims are often meaningless. The only way to know what's actually in the bottle is independent lab testing from a recognised laboratory. Ask the brand: can you show me a Certificate of Analysis?
3. Understand the Dose
Pay attention to whether the FU count is per capsule or per serving (2+ capsules). A product claiming 5,000 FU per 2 capsules gives you only 2,500 FU per capsule — half the potency of a product offering 5,000 FU per single capsule.
4. Check for Vitamin K
Nattokinase from fermentation may contain vitamin K2. If you take warfarin or other blood thinners, look for products labelled "vitamin K2 removed" or "NSK-SD" to avoid interactions.
5. Holland and Barrett, Amazon, or Direct?
The retailer matters less than the product itself. Holland and Barrett stocks nattokinase, but we have not tested their own-brand product. Amazon UK has a wide selection — as our testing shows, some pass and most don't. Wherever you buy, apply the same criteria: FU count, third-party testing, and per-capsule dosage.
Your Nattokinase Checklist
Before you buy, check every box.
- FU on the label — not just milligrams. FU measures actual enzyme activity.
- At least 5,000 FU per capsule — so 2 capsules reaches the clinically studied 10,000+ FU/day.
- Per capsule, not per serving — some brands split the dose across 2–3 capsules to inflate the headline number.
- Third-party lab testing — from an independent lab like SORA Laboratories, not the brand's own tests.
- Vitamin K2 status — check if K2 is removed, especially if you take blood thinners.
- Avoid labels with only milligrams — no FU means no way to verify enzyme potency.
- Avoid unverified claims — if a brand can't show a Certificate of Analysis, move on.
- Avoid low-FU products — anything under 2,000 FU per capsule is too low based on clinical evidence.
It's Not Just a UK Problem
Our Amazon UK testing found 3 out of 4 brands failing. But earlier testing of US brands by SORA Laboratories told a similar story — 4 out of 5 American brands also failed to deliver their claimed potency. This is an industry-wide issue, not limited to any single market or retailer.
The fundamental problem is that nattokinase is an enzyme. Enzymes are proteins that lose their activity when exposed to heat, moisture, or improper storage. Many manufacturers either start with low-quality raw material, don't test their finished products, or lose potency somewhere in the supply chain. Without independent verification, the consumer has no way to know.
"Only 2 out of 9 brands we've tested across the US and UK delivered their claimed potency. That's a 78% failure rate."Based on SORA Laboratories testing data, 2025–2026
For a full breakdown of the science behind nattokinase — including clinical trials, mechanism of action, and dosage research — see our complete nattokinase guide.
Frequently Asked Questions
Based on independent SORA Laboratories testing of the top 4 Amazon UK nattokinase brands, Natural Foundation Supplements is the only brand that passed. It delivered over 6,720 FU per capsule against a 5,000 FU label claim — 34% more than promised. The other 3 brands delivered between 18% and 28% of their claimed potency.
Holland and Barrett stocks nattokinase supplements. However, we have not independently tested their product. When buying from any retailer, always check for FU (Fibrinolytic Units) on the label, look for third-party lab testing, and ensure the product delivers at least 5,000 FU per capsule based on clinical research.
Look for three things: (1) FU on the label — this measures actual enzyme activity, not weight. (2) Third-party lab testing from an independent laboratory. (3) A minimum of 5,000 FU per capsule, based on clinical trials that used 10,800 FU/day.
Nattokinase is a delicate enzyme sensitive to heat, moisture, and improper storage. Many manufacturers use low-quality raw materials, don't test finished products, or lose potency through poor handling. The supplement industry has less regulation than pharmaceuticals, making independent testing essential.
FU stands for Fibrinolytic Units — a measure of the enzyme's clot-dissolving activity. This is far more important than milligrams. A label showing only mg without FU tells you nothing about potency. The largest clinical trial used 10,800 FU per day and found significant cardiovascular benefits.
Natto has been eaten daily in Japan for over 1,000 years. Modern toxicology studies found no adverse effects at 100x typical human doses. Clinical trials up to 12 months reported no notable side effects. However, nattokinase has blood-thinning properties — don't combine with anticoagulant medications without medical supervision. Read more in our complete guide.
The largest clinical trial (1,062 participants, 12 months) found significant benefits at 10,800 FU/day, while 3,600 FU/day was ineffective. Look for capsules with at least 5,000 FU each and take 1–2 daily. Always consult a healthcare professional before starting any supplement.