Some peptides from fish are claimed to lower blood pressure by blocking an enzyme (ACE) that tightens blood vessels. The human trials are few and small, and they tested different products.
Limited human evidence
One small randomised trial (29 people, 4 weeks) found blood pressure fell by roughly 9 mm Hg systolic and 5 mm Hg diastolic against no change on placebo, with blood markers consistent with ACE inhibition. Nothing else in this hub replicates it.
Limited human evidence
One randomised trial in 100 patients found lower diastolic and mean arterial pressure plus better blood sugar and cholesterol over three months. Patients stayed on their usual medicines, and the abstract gives no dose.
Limited human evidence
A single 20 g dose in nine people did not improve endothelium-dependent dilation, while whey hydrolysate did. It says nothing about blood pressure or longer use.
Verdicts reflect only the studies summarised on this site, last reviewed November 9, 2026. See how verdicts are set.
| Study | Design | Peptide |
|---|---|---|
| Oliveira et al., 2020 | Human trial (controlled) | Fish protein hydrolysate |
| Zhu et al., 2010 | Human trial (controlled) | Marine (fish-derived) collagen peptides |
| Kawasaki et al., 2000 | Human trial (controlled) | Valyl-tyrosine (sardine peptide) |
Oliveira et al., 2020 · Int J Food Sci Nutr · 9 healthy adults
Whey protein hydrolysate increased endothelium-dependent dilation of a blood vessel 30 minutes after the dose compared with placebo. Fish protein hydrolysate did not. In a lab assay the fish product had higher total antioxidant capacity than the whey product.
Zhu et al., 2010 · Am J Med Sci · 100 patients with type 2 diabetes and primary hypertension (50 per group) plus 50 healthy comparison subjects, in China
Compared with patient controls, the marine collagen peptide group had lower fasting blood glucose, HbA1c, diastolic blood pressure, mean arterial pressure, triglycerides, total and LDL cholesterol and creatinine, and higher HDL cholesterol and insulin…
Kawasaki et al., 2000 · J Hum Hypertens · 29 adults with high-normal blood pressure or mild hypertension
On the sardine peptide, systolic and diastolic blood pressure fell by 9.7 and 5.3 mm Hg after one week and by 9.3 and 5.2 mm Hg after four weeks (P < 0.001), with no change on placebo. Pressure crept back up during the recovery period. Blood markers fitted…
Educational information only. It is not medical or legal advice, and nothing here is a recommendation to use any peptide. Talk to a clinician before starting a supplement or treatment.