Nattokinase has an unusual origin for a modern supplement: a sticky, strong-smelling traditional Japanese breakfast food. Understanding where it comes from and how it is measured tells you most of what you need to compare products sensibly.
This is part of our guide to choosing a nattokinase supplement.
It starts with natto
Natto is a traditional Japanese food made by fermenting cooked soybeans with a bacterium called Bacillus subtilis (var. natto). The result is stringy, pungent, and an acquired taste — but it has been eaten in Japan for centuries.
During fermentation, the bacteria produce an enzyme. In the 1980s a researcher named Dr Hiroyuki Sumi identified and named that enzyme nattokinase. It is this enzyme, extracted and concentrated, that ends up in supplements — so you get a standardised amount without eating the natto itself.
How supplement nattokinase is made
Commercial nattokinase is produced by controlled fermentation of soybeans with Bacillus subtilis, after which the enzyme is extracted, purified and standardised. Two consequences follow that matter to you as a buyer:
- It contains soy. Because it is fermented from soybeans, nattokinase is a declarable soy allergen. This should always be stated on the label — and on ours, it is.
- It is typically suitable for vegans. The enzyme is produced by bacteria fermenting a plant, with no animal input — unlike some enzymes derived from animal sources.
Why it is measured in FU, not just mg
This is the part worth understanding properly, because it is where a lot of nattokinase products mislead — sometimes deliberately.
Nattokinase is an enzyme, and what matters about an enzyme is its activity, not its weight. So nattokinase is measured in fibrinolytic units (FU) — a standardised measure of enzymatic activity — rather than by milligrams alone.
Here is why that matters. Two products could both declare "100mg of nattokinase" and yet deliver very different activity, because the enzyme concentration within that 100mg can vary. The FU figure cuts through that: it tells you the standardised activity. Most of the research uses 2000 FU as the reference level.
The practical takeaway: when you compare nattokinase products, compare the FU. A product that only lists milligrams, with no FU figure, is not giving you the number that actually matters — and there is usually a reason for that omission. Our guide to choosing a nattokinase supplement covers this and the other checks in full.
A note on what we can and can't tell you
You will find plenty of claims online about what nattokinase does. We'll be straight with you: nattokinase has no authorised health claim in Great Britain, so we are not permitted to tell you what it does for your body — and neither is any other UK seller, whatever their product page says. If you have seen a bold promise on a nattokinase page, that is a reason to trust the seller less, not more.
There is published research you can read and weigh for yourself. It is not the same as an authorised claim, and nattokinase does have genuine safety considerations for some people — which is why we point every reader to the safety guide before buying. For most people it is a short check; for a few it is important.
Our product, honestly
If nattokinase is what you're after, our Nattokinase Complex is built for the research-led buyer: 100mg standardised to 2000 FU — the researched activity level — formulated as a complex rather than a bare isolate, with the soy allergen clearly declared, in a vegan capsule made in the UK to GMP standards.
We put the FU on the front because it is the number that matters, and we point you to the safety information because good products don't need to hide it. Have a quick read of the safety guide, and if it's right for you, we'd be glad to be your source.
Read next: the full buyer's guide, or browse our cardiovascular range.
Always read the label. Food supplements are not a substitute for a varied and balanced diet and a healthy lifestyle. This article is general information, not medical advice.
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