1. ACE inhibition is a research endpoint, not a clinical blood-pressure result

Lactic-acid-bacteria proteolysis can release peptides from milk proteins, and some peptides inhibit angiotensin-converting enzyme (ACE) in laboratory assays. An ACE-inhibition result does not show that drinking a fermented product lowers blood pressure after digestion and absorption. Peptide identity and dose, gastrointestinal stability, bioavailability, and human physiology all require separate evaluation. Nor should specific tripeptides such as VPP or IPP be assumed to occur in every fermented milk.

2. The primary study tested a defined goat-milk fermentation

Rubak and colleagues fermented reconstituted goat milk (11% w/v) with lactic acid bacteria isolated from fermented foods and breast milk. A 2% inoculum was incubated at 37°C until pH 4.6; the researchers analyzed the centrifuged supernatant for ACE-inhibitory activity and peptides. The sample fermented for 48 hours with Lactococcus lactis ssp. lactis BD17 had the highest activity in that experiment: 60.33% inhibition, with an IC50 of 0.297 ± 0.10 mg/mL. LC-MS/MS identified peptide sequences, with candidate ACE-inhibitory status assessed using prior literature. These are in vitro findings for one strain and one goat-milk protocol; the study did not measure blood pressure in consumers.

3. Identified peptide candidates are not demonstrated antihypertensive doses

Detecting peptide sequences and observing enzyme inhibition do not establish that those peptides remain active through digestion, are absorbed, or reach an effective concentration in the body. The cited review surveys bacterial proteolysis systems and ACE-inhibitory peptide research in fermented milk; it also frames predicted activities as requiring further experimental validation. Mechanistic plausibility and an assay result should therefore not be converted into a claim of proven human efficacy.

4. Expert perspective: blood-pressure claims need human trials

Neither source is a randomized human blood-pressure trial. They do not show that fermented goat milk prevents or treats hypertension, or can replace medication. Clinical evaluation would need to address peptide stability and bioavailability as well as use an appropriate control, defined intake, sufficient duration, reliable blood-pressure measurements, and safety monitoring. The supported conclusion is narrower: under one specified fermentation protocol, a goat-milk sample displayed ACE-inhibitory activity in vitro and contained peptide candidates for further study.

Sources: Angiotensin-I-converting enzyme inhibitory peptides in goat milk fermented by lactic acid bacteria isolated from fermented food and breast milk / Antihypertensive potential of fermented milk: the contribution of lactic acid bacteria proteolysis system and the resultant angiotensin-converting enzyme inhibitory peptide