Nattokinase: The Heart Health Supplement on Everyone’s Tongue
When it comes to cardiovascular health, few supplements have sparked as much public interest — or confusion — as nattokinase. Let's unpack...
When it comes to cardiovascular health, few supplements have sparked as much public interest — or confusion — as nattokinase.
This enzyme, derived from Japanese fermented soybeans, has achieved near-legendary status for its potential to improve, or even reverse, atherosclerosis.
But the hype surrounding nattokinase is often matched by a lack of understanding — both about how it works and whether it actually works.
So, in today’s newsletter, we’re going to unpack that.
Here’s the Roadmap:
Origin and Lore of natto, the natural source of nattokinase.
Human Data suggesting that nattokinase may improve, or even reverse, atherosclerosis.
Mechanisms by which nattokinase is thought to support cardiovascular health.
Dosing protocols — which, as we’ll see, play a crucial role in determining nattokinase’s potential efficacy.
Finally, I’ll help you built a 5-ingredient Heart Health Stack, drawing from past letters and scientific literature.
Origin & Lore of Nattō
Nattō is a traditional Japanese fermented soybean, created by fermenting soybeans with Bacillus subtilis bacteria.
There are several stories about the origin of nattō, but it’s clear that its consumption dates back about 1,000 years.
One account traces it to the samurai Minamoto no Yoshiie in 11th-century Japan. According to the legend, his troops were boiling soybeans for their horses when they were attacked!
In a hurry, they packed the beans into straw bags and fled. By the time they opened the bags days later, the beans had naturally fermented — and nattō was born.
From Lore to Longevity
In the centuries since, nattō intake has been associated with longer life and lower rates of cardiovascular disease.
For example, one study followed about 29,000 participants for 16 years and tracked cardiovascular mortality.
People in the highest quartile of nattō consumption, compared with those in the lowest quartile, had a 25% lower risk of dying from cardiovascular disease (HR = 0.75), even after adjusting for relevant covariates.
Because this is an observational study, you could reasonably worry about “healthy‑user bias.”
I would.
But what’s especially interesting is that the researchers found no significant associations between cardiovascular mortality and total soy protein intake or other soy foods — the signal was specific to natto.
Let that fact ferment for a second.
This pattern supports the idea that there may be something uniquely beneficial about natto itself.
Enter nattokinase — an enzyme made during the fermentation process by the Bacillus subtilis bacteria — and the cardio-protective enzyme at the heart of today’s letter.
High-Dose Nattokinase Reverses Atherosclerosis
In a study involving 1,062 participants, researchers administered 10,800 units of nattokinase per day over the course of a year.
They observed something striking: a measurable regression of atherosclerosis.
Specifically, they used ultrasound imaging to measure plaque in the carotid arteries (which carry blood from the heart to the brain). They assessed both carotid intima-media thickness (CCA-IMT) and the carotid plaque surface area (CPS) — metrics for evaluating atherosclerosis.
After 12 months of nattokinase supplementation, carotid intima-media thickness decreased by 21.7%, and plaque surface area decreased by 36%.
These dramatic changes speak for themselves.
Lipid Changes
The researchers also measured lipid changes in participants and found:
15.7% reduction in Triglycerides
18.1% drop in LDL-Cholesterol
15.8% increase in HDL-Cholesterol.
Limitations & Caveats
That said, it’s important to note that this was not a randomized controlled trial and lacked a control group.
Participants were compared to their own baseline measurements. So, while the results are promising, confounding variables can’t be ruled out.
Still, I find the findings promising, if not compelling — especially given that nattokinase is a widely available and common supplement.
Dose Threshold?
One addition I appreciated in this study’s discussion was the authors’ commentary dosing.
We will discuss this in greater depth below, but they clearly explained the inconsistent literature by noting that prior studies, including randomized controlled trials, that failed to show benefits typically used much lower doses.
For instance, some trials used just 2,000 units per day, compared to 10,800 units in this trial.
In a word, these findings are “promising” — not definitive, but certainly worth your attention.
But just like a plate of crispy natto fritters, this is only the appetizer!
In the rest of this letter —for StayCurious Premium members — we’ll dive into:
Cardioprotective mechanisms behind nattokinase
Dosing protocols & sourcing (brand recommendations)
How to Build a Heart-Health Stack
This is a deep-dive letter nat-to be missed.
If you’re not already part of the premium community, now’s the time to join — it’s just $8/month, or less than 67 cents per letter.
