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Bonito Peptides (Katsuobushi Oligopeptide / Val-Tyr)
Short ACE-inhibitory peptides from enzyme-digested dried bonito (Katsuobushi) fish muscle — notably the dipeptide Val-Tyr ("VY") and the prodrug-type pentapeptide LKPNM — sold as a food-derived supplement for blood pressure. Honest appraisal: a handful of small, mostly Japanese, often industry-linked RCTs show a modest blood-pressure drop in people with mild/high-normal hypertension, on the same ACE-inhibition mechanism as related fish/sardine and milk (lactotripeptide) peptides. The effect is small, the trials are small, and benefit concentrates in (pre)hypertensive people — not normotensives.
What the evidence says
Most Bonito Peptides studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality randomised trials published 1992–2020 with a typical study size of 29 participants.
Based on 12 studies · 5 RCTs · 128 total participants
Confidence
Moderate confidenceBy outcome
Scores low-moderate/Emerging because a few small, short, mostly Japanese and often industry-affiliated RCTs show only a modest blood-pressure drop in (pre)hypertensives, with no meta-analyses and a plausible ACE-inhibition mechanism.
Bonito peptides are short peptides released when dried bonito (Katsuobushi, a Japanese fish seasoning) muscle protein is digested with enzymes such as thermolysin.
The mixture (a "katsuobushi oligopeptide") contains several angiotensin-I-converting-enzyme (ACE) inhibitory peptides isolated from the digest — the dipeptide Val-Tyr ("VY", also derivable from sardine muscle) and the pentapeptide Leu-Lys-Pro-Asn-Met (LKPNM) are the most studied.
LKPNM is a "prodrug-type" inhibitor: it is itself a weak ACE inhibitor but is cleaved by ACE to LKP, an ~8-fold more potent inhibitor, giving a delayed, prolonged effect.
Mechanistically this is the same renin-angiotensin-system target as ACE-inhibitor drugs and as milk-derived lactotripeptides (VPP/IPP) — but the food peptides are far weaker. The honest human evidence is thin and modest.
The clearest signal comes from small Japanese double-blind RCTs in mild/high-normal hypertension: a Val-Tyr/sardine drink lowered systolic BP by roughly 9 mmHg and diastolic by ~5 mmHg over 4 weeks in one ~29-person trial, and a sardine-peptide vegetable drink lowered SBP ~7-8 mmHg in another.
Dried-bonito-broth crossover studies in elderly subjects show smaller SBP reductions (and a fall in the oxidative-stress marker 8-OHdG). Against this, human pharmacokinetic work shows Val-Tyr is absorbed intact but did NOT produce an acute BP change at the doses tested, and effects in older/aged animals are blunted.
The trials are small, short, geographically narrow, frequently funded by or affiliated with the manufacturers, and prone to publication bias — exactly the pattern seen across food-derived ACE-inhibitory peptides.
Treat this as a modest, food-grade lifestyle adjunct for blood pressure, not a substitute for antihypertensive medication. Overall evidence is emerging/low-moderate.
Bonito-derived peptides (Val-Tyr, LKPNM and others) competitively inhibit angiotensin-I-converting enzyme in vitro — the same renin-angiotensin-system target as ACE-inhibitor drugs, reducing formation of the vasoconstrictor angiotensin II.
LKPNM is a weak inhibitor that ACE itself cleaves to LKP, an ~8-fold more potent ACE inhibitor — giving a delayed, prolonged blood-pressure effect after oral intake in animal models.
Beyond ACE inhibition, related peptides (Val-Tyr, sardine Met-Tyr) show antiproliferative effects on vascular smooth muscle and endothelial antioxidant induction in cell models, and human broth studies report lower oxidative-stress markers — proposed but not established contributors.
How Bonito Peptides works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Avoid — the peptides are derived from fish muscle.
Safe as a food, but monitor blood pressure for additive lowering and discuss with a clinician.
Likely safe as a food-derived peptide at culinary/labeled doses; not specifically studied — choose mercury-low, well-sourced products and consult a clinician.
Same renin-angiotensin-system target; theoretical additive blood-pressure lowering. The effect of the peptides is small, but monitor BP if combining.
ACE-inhibitor-class mechanisms can raise potassium; additive risk is theoretical and minor at food-peptide doses, but relevant with prescription RAAS drugs.
Tip: Trials reported no abnormal hematology, blood chemistry, urinalysis, heart rate, or weight changes.
Tip: Avoid if allergic to fish/bonito/sardine.
Bonito Peptides has an evidence score of 3.5/10 — emerging evidence based on 12 indexed studies. Short ACE-inhibitory peptides from enzyme-digested dried bonito (Katsuobushi) fish muscle — notably the dipeptide Val-Tyr ("VY") and the prodrug-type pentapeptide LKPNM — sold as a food-derived supplement for blood pressure. Honest appraisal: a handful of small, mostly Japanese, often industry-linked RCTs show a modest blood-pressure drop in people with mild/high-normal hypertension, on the same ACE-inhibition mechanism as related fish/sardine and milk (lactotripeptide) peptides. The effect is small, the trials are small, and benefit concentrates in (pre)hypertensive people — not normotensives. Representative study: PMID 10962520.
The commonly studied dose of Bonito Peptides is Trials used ~1.5-3 mg Val-Tyr/day (e.g. a 3 mg VY drink, twice daily), or labeled katsuobushi-oligopeptide products providing the equivalent; follow product labeling. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Timing is flexible for Bonito Peptides — consistent daily use matters more than the time of day. Studied as a daily drink or capsule; the prodrug-type peptides act on a delayed timescale, so consistent daily intake matters more than time of day.
Bonito Peptides is generally well-tolerated and considered safe for most healthy adults at recommended doses. Reported side effects are uncommon and include none notable in trials, allergic reaction (fish-allergic individuals). Use caution if any of these apply to you: Fish allergy (bonito/sardine-derived); Caution if already on ACE-inhibitor / antihypertensive medication (theoretical additive blood-pressure lowering).
Glycomacropeptide
Mostly mechanism / observationalA 64-amino-acid peptide released from kappa-casein during cheese-making, sold both as a whey-derived satiety supplement and (amino-acid-fortified) as a low-phenylalanine protein for PKU. Honest appraisal: the appetite/satiety evidence is genuinely mixed — several acute RCTs found NO effect of GMP itself on CCK, satiety ratings, or food intake, while a few found small reductions in energy intake. Its established, evidence-supported use is as a near-phenylalanine-free protein substitute in phenylketonuria, where it works as well as (not clearly better than) amino-acid formulas.
Lactotripeptides
Mostly mechanism / observationalTwo milk-casein-derived tripeptides — Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP) — produced by fermenting milk with Lactobacillus helveticus or hydrolysing casein. They inhibit ACE in vitro and have been studied extensively for blood pressure. Honest appraisal: multiple meta-analyses find a small, statistically-significant drop in systolic/diastolic BP, but the effect is modest, heterogeneous, larger in Japanese than Western trials, and dented by clear publication bias plus outright-null trials (e.g. the Dutch Engberink RCT).
Casein Hydrolysate
Mostly mechanism / observationalA milk-derived bioactive peptide — a tryptic hydrolysate of bovine αs1-casein standardized to the decapeptide α-casozepine (Lactium) — marketed for stress, anxiety, and sleep. Honest appraisal: the mechanism is real and food-derived (α-casozepine binds the benzodiazepine site of the GABA-A receptor in vitro), and a handful of small human RCTs show modest reductions in stress symptoms and cortisol plus some sleep-diary improvements. But several trials are industry-linked, two well-designed sleep RCTs were null on their primary endpoint, and effects are small. Well-tolerated; this is an ordinary dietary supplement, not a drug.
Soy Peptides
Mostly mechanism / observationalShort, bioactive fragments enzymatically cleaved from soy protein — soy protein hydrolysates plus named peptides like lunasin and soy ACE-inhibitory peptides. Unlike whole soy protein (a complete protein with an FDA cholesterol claim) or soy isoflavones (phytoestrogens), these are specific peptide fragments studied for cholesterol, blood pressure and antioxidant effects. Honest appraisal: the evidence is mostly in-vitro and animal. The one published human RCT (lunasin) was null. Emerging, not established.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 12 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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