Reading · Weight Health with Ashley Koff RD

If your algorithm has started serving you sticky, stringy, stinky (!) beans next to your GLP-1 or longevity content, you’re not imagining it. Nattokinase, the enzyme found in natto (a fermented soybean dish that’s been a Japanese breakfast staple for over a thousand years), is suddenly everywhere in the wellness conversation. And per usual, the internet is either overselling it as a miracle solution or missing its value entirely.

I want to do what I always do: land in the middle, with the actual science, and connect it to something you might not expect but come to me for help with: weight health.

Natto is made by fermenting soybeans with Bacillus subtilis. That fermentation produces nattokinase, an enzyme that’s been studied for decades for its role in supporting healthy clot-clearing (fibrinolytic) activity, meaning it helps your body manage fibrin. Research has shown nattokinase supports blood flow and may modestly support healthy blood pressure, largely through two mechanisms: relaxing blood vessels and reducing blood viscosity.

I want to be clear about something, because I’m the backwards DR and I’d rather ruin the hype than let you waste your money: this is “may support,” not “will cure.” The research base has grown, but it’s still made up largely of small trials. Nattokinase is a food-derived compound with promising circulation-supporting mechanisms, not a replacement for a comprehensive assessment and personalized plan with the right tools for your body based on the insights generated.

We hear heart disease and “blood flow problem” and are taught to think only of plaque: the slow buildup of cholesterol, fat, and calcium along artery walls that physically narrows the pipe over years or decades. That’s atherosclerosis, and it’s a structural problem.

Fibrin is a different and reveals a different but adjacent ecosystem issue. It’s the protein your blood uses to form clots in real time, as part of your normal clotting response. That’s essential when you’re bleeding. The issue is when fibrin builds up or lingers longer than it should, it makes blood thicker and stickier moment to moment, even in vessels that have no plaque in them at all. Nattokinase’s research is about this fibrin side of circulation, the fluid dynamics of your blood itself, not the structural, plaque side. Both affect blood flow. They are not the same mechanism, they are not addressed by the same interventions, and a food or supplement that supports one may not directly affect the other.

This distinction is exactly why I don’t want you walking away thinking “nattokinase equals healthy arteries.” But rather, in certain circumstances, nattokinase is the more appropriate tool (or eating stinky natto ;)! It may support one piece of a much bigger circulation picture.

This is where my “rolling hills, not peaks and valleys” approach to blood sugar optimization connects directly to fibrin. When glucose runs high, it attaches to the fibrinogen protein itself (the raw material your body uses to build fibrin), this is called glycation. Glycated fibrinogen tends to form a denser, harder-to-break-down clot mesh. Research in people with diabetes has shown that both high and low blood sugar extremes are linked to this same unfavorable, harder-to-clear fibrin structure. It’s not just “high is bad.” It’s instability itself, the peaks and the valleys, that seems to matter most.

There’s a second piece too: when blood sugar runs high, your body pulls extra water into your bloodstream to help flush the excess glucose out through your kidneys. That’s part of why frequent urination and thirst show up with high blood sugar. The practical effect is that you can end up mildly dehydrated at the exact same time your fibrin is behaving less favorably, and dehydration on its own thickens your blood and makes it move less efficiently. Two problems stacking on top of each other.

This is one more reason steady, rolling-hills blood sugar and steady hydration belong in the same conversation as nattokinase, nitric oxide, and estrogen when we talk about blood flow. They’re not separate levers. They’re all touching the same system.

Weight health isn’t just about the number on the scale. It’s about whether your metabolic tissue is actually getting what it needs to function. Your muscle, your gut lining, your liver, your fat tissue itself: all of it depends on circulation to deliver oxygen, nutrients, and hormonal signals, and to clear out what doesn’t belong.

This is the same lens I use for GLP-1, GIP, PYY, CCK and amylin. Your body’s own weight-health hormones don’t work in isolation. They work through a delivery system. If that delivery system (your vasculature) is sluggish, the whole framework underperforms.

Specific to GLP-1, whether you are optimizing your own or on a GLP-1 medication, this hormone and your natto might be two peas in the same soybean pod. GLP-1 receptors sit directly on the cells lining your blood vessels, and research shows GLP-1 activity there helps calm vascular inflammation and oxidative stress at the vessel wall itself. Separately, nattokinase has shown its own anti-inflammatory action on those same endothelial cells. Your GLP-1 and your natto may both be showing up to work on vascular inflammation.

This matters for a lot of my patients, especially the ones navigating hair changes during a weight-loss phase (see my recent article here on hair loss). Hair follicles are some of the most metabolically active tissue in your body. They need a robust capillary blood supply to stay in the anagen (growth) phase. When circulation to the scalp is compromised, follicles are more likely to shift into shedding phases early.

This doesn’t mean nattokinase is a hair-growth supplement. It isn’t, and I won’t sell it to you as one. But it does mean that “how’s my circulation” is a legitimate question to ask when you’re troubleshooting hair thinning during your weight-health journey, not just “how’s my protein” or “how’s my ferritin,” though those matter too. And why for women going through peri-menopause the hair-hormone-cardiovascular risk is truly are interconnected (more on estrogen’s role in a moment).

If soy is off the table for you, whether allergy, sensitivity, or just personal preference, you’re in luck. Because nattokinase is produced by the bacteria doing the fermenting rather than being a structural part of the soybean itself, manufacturers have started fermenting Bacillus subtilis on chickpeas instead. Lab comparisons have found chickpea-fermented substrate can produce nattokinase activity comparable to, and in some studies higher than, traditional soy substrate, while producing less of the sticky byproduct that soy fermentation generates. That’s genuinely useful, practical innovation, not just a marketing spin on the word “natto.”

If you go this route, look for third-party testing and a clear FU (fibrinolytic unit) dose on the label, same as you would with soy-based nattokinase. I personally fell in low with adding TOKU nattokinase to my smoothies or hot cocoa (the chocolate is the first chocolate supplement that doesn’t taste not-chocolately to me … that was a win).

Because I use this along with my total nutrition plan and to date have zero scores on soft and hard plaque, I got excited and I asked them for an affiliate code so I could give my community a discount — its BNP20 used here https://tokuhealth.com if you want to try it. And let me know what you think.

Supplements are never the whole picture in my world; the goal is for your nutrition to give your body what it needs to run optimally, and we do that with total nutrition, food plus supplements.

Nitric oxide (NO) is your body’s own natural vasodilator, made in the lining of your blood vessels. It’s a completely different mechanism from nattokinase’s clot-clearing action, but the outcome, better blood flow, overlaps.

Foods that support your body’s nitric oxide production include:

Nitrate-rich vegetables: beets, arugula, spinach, and other leafy greens
Citruline-rich foods: watermelon (rind included, if you’re brave)
Polyphenol-rich foods: pomegranate, dark chocolate/cacao, berries
Allium vegetables: garlic, onions

Nitric oxide production isn’t static across your life. It’s significantly influenced by estrogen. Estrogen activates the enzyme (eNOS) responsible for generating nitric oxide in your blood vessel lining. As estrogen declines during perimenopause and menopause, nitric oxide production drops with it, independent of chronological age. That’s a meaningful part of why cardiovascular risk accelerates around menopause, and it’s also a contributor to some of the circulation symptoms women report during this transition: cooler hands and feet, skin changes, and yes, hair thinning.

This is exactly the kind of connection I mean when I talk about weight health versus weight loss. Your hormones are a network, not a single lever. GLP-1 and estrogen should be considered for their impact on nitric oxide and fibrin balance.

You don’t need to add a nattokinase supplement to your routine to benefit from this article. You do need to assess circulation and what could be impacting yours, as well as consider the role of fibrin and nitric oxide in your weight health.

That’s the backwards DR approach: as an RD I work forward from your body’s current signals and your choices, not backward from the diagnosis …or trend.

Nattokinase Is Having a Moment. Here's Why Your Weight Health (and Your Heart and Hair) Should Care.

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