Does Natto Help With Sleep?

About 30% of US adults sleep fewer than seven hours a night, and many turn to unusual sources — including fermented foods — for answers.

Natto, the Japanese fermented soybean that gives us nattokinase, contains several compounds — γ-polyglutamic acid, vitamin K2, live probiotic bacteria — that could plausibly influence sleep. But does eating natto, or taking a nattokinase supplement, actually improve how you sleep? The research answers this more precisely than most searchers expect.

Table of Contents

1. What's Actually in Natto That Could Affect Sleep?
2. What the Direct Research Shows on Natto and Sleep
3. The Gut-Sleep Pathway — Where Natto Most Likely Helps
4. Nattokinase Supplements vs. Natto the Food — A Critical Distinction
5. Practical Reality — What to Do If Sleep Is Your Goal
6. BioAbsorb Nattokinase — What This Product Is For
7. Frequently Asked Questions
8. Conclusion
9. Research References

What's Actually in Natto That Could Affect Sleep?

Natto is boiled soybeans fermented for 24 hours by Bacillus subtilis var. natto . That fermentation isn't cosmetic — it dramatically changes what's in the beans. Total isoflavone content rises to 1.62 times the level in raw soybeans, and the bioavailable aglycone forms increase 3.07-fold. Multiple sleep-relevant compounds appear or become more concentrated in the process.

Five components matter for the sleep question:

• Vitamin K2 (MK-7): Natto is the richest natural source in the food supply, delivering roughly 900–1,100 μg per 100g serving. A traditional Japanese portion of 40–50g provides several hundred μg. A recent meta-analysis found habitual natto intake raises serum MK-7 with a very large effect size (Cohen's d = 2.10).
• γ-Polyglutamic acid (γ-PGA): The sticky, stringy polymer that makes natto notorious. Chemically, it's chains of glutamic acid — a direct precursor to GABA, the brain's primary calming neurotransmitter.
• Live Bacillus subtilis natto: One of only 40 probiotic organisms recognized by the US FDA. Studies show it reaches the intestine alive and produces enzymes and metabolites there.
• Tryptophan: Present in soybeans; converted in the gut to serotonin, which is the direct precursor to melatonin.
• Nattokinase: The fibrinolytic enzyme. A typical 60g portion of natto can contain up to 2,000 FU. This is the component isolated for supplements.

None of these components is unique to natto in isolation — you can get vitamin K2 from aged cheese, tryptophan from many protein sources. What natto uniquely combines in one food is fermentation-derived γ-PGA, exceptionally high concentrations of MK-7, and a live probiotic organism that survives intestinal transit. That combination is why "does natto help with sleep?" is a more interesting question than "does soy help with sleep?"

What the Direct Research Shows on Natto and Sleep

The direct evidence splits neatly into three buckets: whole-food natto, isolated nattokinase, and adjacent studies on natto's individual components. The pattern that emerges is important because it distinguishes what you'd get from the food versus the supplement.

Whole-food natto: The most direct study is a 4-week randomized, double-blind, placebo-controlled trial in 30 healthy adults published in Food & Nutrition Journal (2025). Participants took 3g/day of natto powder or a placebo powder made from the same soybeans without fermentation. The natto group showed within-group improvements on 4 of 5 OSA-MA sleep factors (sleepiness upon waking, sleep initiation, dreaming, and refreshment) and a statistically significant reduction in drowsiness. Critically, though, between-group comparisons did not reach statistical significance — meaning the placebo soybean powder also improved sleep, and the researchers couldn't isolate the fermentation effect at this sample size.

Isolated nattokinase: The ICC-PACS trial (Zhang et al., 2025) tested 6 months of nattokinase supplementation in 88 completers with asymptomatic intracranial or carotid stenosis. The mean difference in PSQI score per 6-month period was −1.005 (95% CI −2.096 to 0.065, P = 0.072) — a trend toward improved sleep quality that just missed the conventional statistical threshold. Not a clean positive result. Not a clean null result.

Component-level evidence: The clearest positive signal comes from natto's sticky component, γ-PGA. A 2021 factorial crossover trial in 47 healthy adults tested γ-PGA 600mg, vitamin B6 100mg, and both combined. The combination significantly improved PSQI global scores by −0.52 points (P<0.05) and sleep duration by 0.27 hours (P<0.05). Neither γ-PGA nor B6 alone reached significance — the effect required both. Serum serotonin also rose more in the dual-supplementation group than in either single-supplement group.

Bottom line: no adequately powered RCT has demonstrated that natto or nattokinase produces a statistically significant sleep improvement compared to a matched control. The signals across studies are consistently pointing in one direction, but the effect sizes are modest and the trials are small.

The Gut-Sleep Pathway — Where Natto Most Likely Helps

If natto works for sleep, the mechanism almost certainly isn't the nattokinase enzyme. It's the gut-brain axis — a research area that has expanded rapidly in the last five years.

Serotonin and melatonin production: Around 90% of the body's serotonin is synthesized in the gut, not the brain, primarily by enterochromaffin cells acting on dietary tryptophan. Serotonin is the direct precursor to melatonin, which governs the sleep-wake cycle. Gut bacteria modulate how efficiently this pathway runs, and disruptions to the microbiome can shunt tryptophan away from serotonin production and toward inflammatory kynurenine metabolites instead.

GABA production: Certain Lactobacillus and Bifidobacterium species produce GABA directly. The 2024 Nutrients review (Sejbuk et al.) documented that dietary fiber, unsaturated fatty acids, and polyphenols significantly affect the microbiota's capacity to produce these sleep-regulating metabolites. A 2025 Scientific Reports RCT in 106 healthy adults showed that 8 weeks of a targeted probiotic (Bifidobacterium animalis subsp. lactis BLa80, 10 billion CFU/day) significantly reduced PSQI total scores vs placebo — direct evidence that shifting the gut microbiome can move a validated sleep quality measure.

The natto pathway specifically: γ-PGA supplementation raises serum glutamate and GABA in animal studies, and vitamin B6 is the cofactor that converts glutamate to GABA. Natto delivers γ-PGA in its stringy sticky component; soybeans generally provide vitamin B6. Simultaneously, live Bacillus subtilis natto reaches the intestine and may modulate the microbiome. A 2025 citizen-science RCT in 147 adults (preprint, not yet peer-reviewed) found high-fermented-food diets significantly increased microbial diversity in participants over 50, and while fermented foods didn't independently improve sleep in that trial, the high-fiber arm improved sleep quality significantly (P = 0.03).

The biological pathway from natto to sleep exists and is plausible. What's missing is a large trial specifically designed to test it end-to-end.

Nattokinase Supplements vs. Natto the Food — A Critical Distinction

This is the distinction most searchers miss, and it changes the answer to the original question.

Nattokinase supplements deliver almost none of natto's non-enzyme content. When manufacturers extract nattokinase for capsules, they isolate the fibrinolytic enzyme and leave behind the γ-PGA, the vitamin K2, the live Bacillus subtilis, the tryptophan, the isoflavones, and the soybean matrix. Everything that plausibly links natto to sleep is stripped out. What remains is a targeted cardiovascular supplement with 100–200 mg of nattokinase (typically 2,000 FU activity per capsule).

That's why the direct evidence pattern is what it is. In the ICC-PACS trial, participants took 4,000 FU of nattokinase twice daily — 8,000 FU/day, four times the standard 2,000 FU dose — for 6 months. Even at that dose, the PSQI sleep score improvement of −1.005 points didn't reach statistical significance (P = 0.072). If nattokinase itself had a strong direct effect on sleep, an 8,000 FU/day dose over 6 months should have detected it clearly.

Meanwhile, whole-food natto — with its full complement of γ-PGA, K2, live bacteria, and soy matrix — showed consistent within-group sleep improvements in the 3g/day powder study over just 4 weeks. The signal from the food is stronger than the signal from the isolated enzyme, and the biological explanation is that the sleep-relevant components aren't the enzyme.

The practical implication: if sleep is your primary reason for considering a nattokinase supplement, that supplement is aimed at the wrong target. Nattokinase's evidence base is in cardiovascular outcomes — fibrinolysis, blood pressure, and PAI-1 inhibition — where multiple RCTs including meta-analyses have shown meaningful effects at 2,000 FU/day. Sleep is not what the isolated enzyme is validated for.

Practical Reality — What to Do If Sleep Is Your Goal

The honest recommendation depends on why you're asking. Roughly 30% of US adults report short sleep and around 15% report trouble falling asleep according to the CDC's 2024 data brief, and prevalence is highest (39%) in adults 45–64 — the same age group most interested in cardiovascular supplements. So the sleep-and-nattokinase question often comes from someone weighing both concerns at once.

If sleep is your primary concern: Nattokinase is not the right supplement. Direct interventions with stronger evidence include low-dose melatonin, magnesium glycinate, cognitive behavioral therapy for insomnia (CBT-I), and — where diet permits — a genuine increase in fermented food and dietary fiber intake. A well-studied probiotic strain with GABA-producing activity has shown a mean 3-point PSQI reduction in a 106-adult RCT, roughly triple the effect size seen in the nattokinase trial.

If you want general health benefits and mild sleep support from a food: Eating actual natto 3–5 times per week may support sleep indirectly through gut-microbiota and γ-PGA effects. Traditional Japanese intake is 40–50g/day (about 1–2 tablespoons). Start with a teaspoon if the flavor is new to you. This is a defensible dietary shift with a plausible mechanism and low downside risk in otherwise healthy adults.

If you take warfarin or another vitamin K–antagonist anticoagulant: Whole-food natto is contraindicated. A 40g serving delivers 400–500 μg of vitamin K2 (MK-7), which will significantly interfere with your INR. Nattokinase supplements formulated without vitamin K2 are a different case, but they carry their own theoretical interaction through their fibrinolytic activity — talk to your prescriber before adding either.

If you're already taking nattokinase for cardiovascular reasons: Any sleep benefit is a possible small bonus, not the primary goal. The evidence for the isolated enzyme is centered on fibrinolysis, blood pressure, blood flow and circulation support, and PAI-1 inhibition — not sleep quality. Set expectations accordingly.

BioAbsorb Nattokinase — What This Product Is For

BioAbsorb Nattokinase Enzyme is a cardiovascular support supplement, and being direct about that scope matters. Each capsule delivers 100 mg of nattokinase with 2,000 FU of enzymatic activity — the dose range used most consistently in cardiovascular clinical trials. The formulation uses DRcaps delayed-release capsule technology, which protects the enzyme from stomach acid without the phthalates and plasticizers found in some standard enteric coatings. It's non-GMO, third-party tested for potency, heavy metals, and microbial contaminants, and manufactured in a Canadian GMP-certified facility.

The 180-capsule bottle is a 6-month supply at one capsule daily on an empty stomach — $49.87, or roughly $0.28 per day. The formulation intentionally excludes vitamin K2, which matters for anyone already supplementing K2 separately or taking vitamin K–antagonist medications like warfarin.

Here's the important part for anyone reading this article for sleep-related reasons: this product does not contain γ-PGA, live probiotic bacteria, or vitamin K2 — the components most plausibly responsible for any sleep effects observed in whole-food natto research. It's the isolated enzyme. For sleep-specific support, other approaches have stronger direct evidence. For cardiovascular support with a well-studied 2,000 FU dose, clean allergen-free formulation, and a 6-month supply per bottle, this product is designed for that goal — not for sleep. Being clear about what a supplement is for is more useful than promising benefits the evidence doesn't support.

Frequently Asked Questions

Does eating natto directly cause better sleep?

Whole-food natto has shown within-group sleep improvements in a 30-adult, 4-week trial published in Food & Nutrition Journal (2025), where 4 of 5 OSA-MA sleep factors improved in the natto group. But no trial has demonstrated a statistically significant difference vs a well-matched control. If there's an effect, it's likely modest and works through gut microbiota and γ-PGA rather than the enzyme.

Does taking a nattokinase supplement improve sleep?

Direct evidence is limited. The ICC-PACS RCT (2025) in adults with carotid narrowing showed a mean improvement of 1.005 PSQI points over 6 months at 8,000 FU/day, but this narrowly missed statistical significance (P = 0.072). Nattokinase is not a recommended primary intervention for sleep.

What component of natto might actually help with sleep?

γ-Polyglutamic acid (γ-PGA) is the leading candidate. In a 47-adult factorial crossover trial, γ-PGA combined with vitamin B6 significantly improved PSQI global scores by −0.52 points. Vitamin K2 and gut-microbiome effects are secondary possibilities but haven't been isolated in sleep-specific trials.

Is natto safe to eat at night?

For most people, yes — it's food, and traditional Japanese consumption is 40–50g/day, often at breakfast. But natto contains 900–1,100 μg of vitamin K2 per 100g, so a single serving can deliver 10–15× the safe intake level for vitamin K. If you take warfarin or another vitamin K–antagonist anticoagulant, natto is contraindicated regardless of timing. Consult your prescriber.

Should I take nattokinase or eat natto if I want better sleep?

Neither is a first-choice sleep intervention. If you specifically want to try natto's plausible sleep-related components, the whole food is a better vehicle than the supplement because the food contains γ-PGA and live bacteria that the isolated enzyme lacks. But options like low-dose melatonin, magnesium glycinate, and GABA-producing probiotic strains have far stronger direct evidence — a targeted probiotic reduced PSQI scores by roughly 3 points in a 106-adult RCT, roughly triple the nattokinase trial's effect size.

How much natto would I need to eat for any sleep benefit?

The 4-week natto powder study used 3g/day of powder, roughly equivalent to a small teaspoon. Traditional Japanese daily intake is 40–50g of whole natto (1–2 tablespoons) , delivering 400–500 μg of vitamin K2 and meaningful amounts of γ-PGA. No study has established a clear "sleep dose" of natto — the evidence isn't precise enough for that recommendation yet.

Conclusion

The honest answer is that natto may modestly support sleep through gut-microbiota effects and γ-PGA — but the evidence for direct nattokinase supplementation on sleep is weak, with the best study showing a non-significant P = 0.072 trend. If cardiovascular support at the well-studied 2,000 FU dose is your goal, BioAbsorb Nattokinase is a targeted, K2-free, DRcaps-delivered formulation designed exactly for that. If sleep is what you're actually chasing, the evidence points to other options first.

Research References

1. Nattokinase supplementation for cognitive enhancement in asymptomatic intracranial/carotid stenosis: A randomized controlled trial (ICC-PACS) (Zhang K, et al.). Journal of Stroke and Cerebrovascular Diseases, 2025. Six-month RCT in 88 completers found nattokinase supplementation produced a non-significant trend toward improved PSQI sleep scores (mean difference −1.005, P = 0.072).
2. Improvement of Bowel Movement in Healthy Adults Through Intake of Natto Powder For 4 Weeks — A Randomized, Placebo-Controlled, Double-Blind, Clinical Study (Kikushima K, et al.). Food & Nutrition Journal, Vol. 10 (2025). Small RCT showing within-group improvements on 4 of 5 OSA-MA sleep factors in the natto powder group but no significant between-group differences.
3. Effects of poly-gamma-glutamic acid and vitamin B6 supplements on sleep status: a randomized intervention study (García-García C, Baik I). Nutrition Research and Practice, Vol. 15 (2021). Factorial crossover trial in 47 healthy adults; dual γ-PGA + B6 supplementation significantly improved PSQI global scores (−0.52 points, P<0.05) and sleep duration.
4. The Role of Gut Microbiome in Sleep Quality and Health: Dietary Strategies for Microbiota Support (Sejbuk M, et al.). Nutrients, Vol. 16 (2024). Review documenting how gut microbiota produce SCFAs, tryptophan-derived serotonin, melatonin, and GABA — the metabolites most directly linked to sleep regulation.
5. A double-blinded randomized placebo trial of Bifidobacterium animalis subsp. lactis BLa80 on sleep quality and gut microbiota in healthy adults (Liu Y, et al.). Scientific Reports, Vol. 15 (2025). Eight-week RCT in 106 adults; BLa80 at 10 billion CFU/day significantly reduced PSQI total scores vs placebo.
6. Habitual natto intake elevates serum MK-7 levels, enhances osteocalcin carboxylation, and supports bone density: a meta-analysis of Japanese evidence (Wen Z, et al.). Frontiers in Nutrition, 2025. Meta-analysis showing habitual natto intake produces a very large effect on serum MK-7 (Cohen's d = 2.10).
7. Determination of 14 Isoflavone Isomers in Natto by UPLC-ESI-MS/MS and Antioxidation and Antiglycation Profiles (Xu Y, et al.). Foods, Vol. 11 (2022). Analytical characterization showing fermentation raises total isoflavone content 1.62× and aglycone content 3.07× versus raw soybeans.
8. Association between vitamin K intake from fermented soybeans, natto, and bone mineral density in elderly Japanese men: the Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) study (Fujita Y, et al.). Osteoporosis International, Vol. 23 (2012). Epidemiological study establishing natto — distinctly from tofu or other soy — as a meaningful dietary K2 source.
9. Distinct modulatory effects of high-fiber and fermented-food diets on gut microbiota, immune function, transit time, and sleep quality in a citizen science randomized controlled trial (medRxiv preprint, 2025). Preprint (not yet peer-reviewed); 147-adult RCT showing high-fiber diet significantly improved sleep quality (P = 0.03) and high-fermented-food diet significantly increased microbial diversity in participants over 50.
10. Short Sleep Duration and Sleep Difficulties Among Adults: United States, 2024. Centers for Disease Control and Prevention, NCHS Data Brief No. 559 (2024). US population data: 30.5% short sleep duration, 15.4% trouble falling asleep, 18.1% trouble staying asleep.
11. FastStats: Sleep in Adults. Centers for Disease Control and Prevention, Behavioral Risk Factor Surveillance System (2022). State-level prevalence data on insufficient adult sleep in the United States.

About the Author

David Kimbell is a health writer, digital entrepreneur and former aerospace engineer, based in Ottawa, Canada. He loves translating complex science into clear, actionable guidance for consumers seeking evidence-based solutions.

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Important Disclaimers

Medical Disclaimer: This article provides educational information only and is not intended as medical advice. Always consult with a qualified healthcare provider before starting any new supplement, especially if you have existing health conditions, take medications, or are pregnant or nursing.

FDA/Health Canada Statement: These statements have not been evaluated by the Food and Drug Administration or Health Canada. This product is not intended to diagnose, treat, cure, or prevent any disease.