Nattokinase and vitamin K2: what the evidence says and what I've seen
Nattokinase has measurable effects on blood pressure and fibrin activity. Natto, the food it comes from, is also the richest dietary source of vitamin K2. I have eaten it regularly for thirteen years.
Most people come across nattokinase as a supplement: a capsule dosed in fibrinolytic units, marketed for heart health. I came across it through natto, the Japanese fermented soybean food it is extracted from, and I have eaten it consistently since 2013.
A nattokinase capsule gives you one isolated enzyme. Natto gives you nattokinase alongside vitamin K2 in its MK-7 (menaquinone-7) form, the richest dietary source by a wide margin. That combination is what most supplement marketing misses, and it is the reason I eat the food rather than take the pill.
Understanding the nattokinase benefits means understanding both sides: the enzyme and the vitamin that come packaged together in one fermented food.
A clot-dissolving enzyme from fermented soybeans
Nattokinase is an enzyme produced during the fermentation of soybeans into natto by the bacterium Bacillus subtilis. It was identified in 1987 by Dr Hiroyuki Sumi at the University of Chicago, though natto itself has been consumed in Japan for centuries.
The enzyme breaks down fibrin, a protein involved in blood clot formation. Most of the clinical interest in nattokinase centres on that fibrinolytic activity and its downstream effects on circulation, blood pressure, and clot-related markers.
Supplements are dosed in fibrinolytic units (FU), typically 2,000 to 10,000 per capsule. That measures the enzyme's clot-dissolving activity, but it tells you nothing about what else natto provides as a whole food.
Blood pressure, fibrin, and what the trials measured
I came to nattokinase through the food, not through a blood pressure concern. But blood pressure is where the evidence is strongest, and it is worth looking at closely.
A 2008 randomised controlled trial published in Hypertension Research tested nattokinase in people with pre-hypertension and stage 1 hypertension and found reductions in blood pressure. A 2023 systematic review and meta-analysis in Reviews in Cardiovascular Medicine combined multiple trials and reported consistent reductions in both systolic and diastolic blood pressure, with no serious adverse events reported across the included studies.
Blood pressure is the strongest part of the case for nattokinase benefits. The data is clear enough to state plainly.
Beyond blood pressure, a 2022 clinical study published in Frontiers in Cardiovascular Medicine followed 1,062 participants taking nattokinase for 12 months. Total cholesterol, LDL (low-density lipoprotein) cholesterol, and triglycerides all dropped significantly, and carotid artery plaque size decreased by 36 percent. That study used a dose of 10,800 FU per day, well above the 2,000 to 4,000 FU range used in most other trials, and the lower dose group in the same study showed no significant changes.
There is also research looking at fibrin-related markers such as D-dimer, which is relevant given nattokinase acts directly on fibrin.
Not all studies show benefit in every group. The Nattokinase Atherothrombotic Prevention Study (2021) found no effect on subclinical atherosclerosis in healthy, low-risk individuals. That tells you where nattokinase is less likely to do anything meaningful.
K2 is what most nattokinase articles miss
The search phrase vitamin K2 and nattokinase keeps rising because people are starting to recognise what natto contains. It is not just a source of nattokinase. It is, by a wide margin, the richest food source of vitamin K2 in MK-7 form.
K2 activates two proteins that regulate calcium distribution. Osteocalcin supports bone mineralisation. Matrix GLA-protein (MGP) helps keep calcium out of arteries and soft tissues. A 2014 review in Dermato-Endocrinology described how K2 activates both proteins and how inadequate K2 can result in both weakened bones and calcified arteries at the same time. I have written about the vitamin D3 and K2 benefits in detail, including why the two vitamins work as a pair and what the evidence shows for bone density and cardiovascular protection.
When I eat natto, I get K2 and nattokinase together in one food. If I were supplementing, I would need separate capsules and assume they replicate the same effect. No trial has compared the whole food to isolated supplements head to head, so I cannot say one is superior. I chose the food because it made practical sense, and I stayed with it because the results held up.
One of the overlooked natto benefits is that simplicity. One food, multiple compounds, no stacking required.
What happened to my teeth
I came to natto looking for K2, initially for cardiovascular reasons. At the time, my health was already improving. I had removed grains, processed food, seed oils, and excess sugar. I was eating whole foods and animal-based protein.
But my teeth were still deteriorating. By my mid-forties the enamel at the gum line had worn away and grooves had formed. My dentist filled them and told me the deterioration could not be stopped.
He was wrong.
After I started eating natto regularly, the deterioration stopped. Over the following months, the enamel returned, the grooves smoothed over, and cavities disappeared.
Then I noticed a pattern. Acidic foods would strip the enamel. Consistent natto intake, around 40 grams per day, would see it recover within three to five days. That pattern held for years.
The mechanism aligns with what we know about K2 and mineral metabolism. Tooth enamel is largely mineral, and K2 activates proteins that help direct calcium where it is needed.
This happened alongside a clean diet, and removing damaging inputs came first. Natto was not a fix on top of a poor diet.
I have not needed a dentist in over a decade. This is not a clinical trial. It is a long-term, repeatable personal observation that aligns with known biology.
How much, and in what form
Clinical trials typically use 2,000 to 4,000 FU of nattokinase per day, though the 2022 Frontiers in Cardiovascular Medicine study suggests higher doses may be required for more significant changes.
I eat about 40 grams of natto three times per week. Because vitamin K2 in MK-7 form has a long half-life, roughly two to three days, that frequency maintains steady circulating levels.
If you are trying natto for the first time, the challenge is practical, not scientific. It has a strong smell and texture. If you cannot tolerate it, a nattokinase supplement combined with K2 MK-7 is a reasonable alternative.
My broader position is simple: fix the diet first. Natto or supplements come after that. I have written about what that ancestral approach to eating looks like in practice.
Nattokinase side effects and safety
Nattokinase has fibrinolytic activity. In simple terms, it thins the blood. That is where both its benefits and risks come from.
Anyone taking anticoagulants should not add nattokinase without medical advice. Natto adds complexity because it also contains vitamin K2, which interacts with certain medications. The same applies to people with bleeding disorders or those preparing for surgery.
At standard doses, nattokinase has not shown significant adverse effects in clinical trials. The 2023 systematic review in Reviews in Cardiovascular Medicine found no serious adverse events across the included studies, and the 2022 Frontiers study used doses up to 10,800 FU daily for 12 months without significant safety concerns. If unsure, speak to your doctor.
Why I have kept natto for thirteen years
I was 46, recovering from emergency surgery to remove an infected gallbladder, and trying to rebuild my health after years of following conventional dietary advice. I came to natto through vitamin K2 research on heart health. I stayed because of what it did.
Thirteen years later, the reason I keep natto in my diet has less to do with any single study of nattokinase benefits and more to do with the accumulated effect. My teeth recovered. My cardiovascular markers stayed strong. Natto became a small, consistent part of a broader dietary approach built around whole foods, adequate protein, and the removal of everything processed. That approach is what foundational health comes down to, and natto fits within it as one reliable piece.
If you are looking at natto in the context of metabolic health, the blood sugar supplements article covers the full evidence hierarchy, including where nattokinase and K2 fit alongside magnesium, berberine, and vitamin D3.
