IRW, LRP and LQP: Food-Derived Bioactive Peptides

IRW, LRP and LQP are short peptides released when common dietary proteins are broken down — IRW from ovotransferrin in egg white, LRP and LQP from wheat bran protein. They are covered together because they share an origin, a mechanism, and the same central question about whether supplementing them makes sense.

This guide situates Food-Derived Bioactive Peptides within the broader field of peptide therapy and is written for clinicians. It is clinical education, not medical advice, and nothing here should be read as a treatment recommendation or protocol.

Peptides hidden inside food proteins

Dietary proteins are not merely amino acid sources. When broken down by digestive enzymes or by fermentation, they release short peptide sequences that can carry biological activity of their own — activity the intact parent protein does not have.

This is a genuine and well-established field. The best-known examples are the lactotripeptides IPP and VPP, released from milk casein by fermentation, which have been studied extensively for blood pressure effects and incorporated into functional food products.

IRW comes from ovotransferrin, an egg white protein. LRP and LQP come from wheat bran protein. All three are tripeptides — three amino acids — identified by screening protein hydrolysates for activity.

ACE inhibition, and what else

The common thread is inhibition of angiotensin-converting enzyme. ACE converts angiotensin I to the vasoconstrictor angiotensin II and degrades the vasodilator bradykinin, so inhibiting it lowers blood pressure. This is the mechanism of an entire class of widely prescribed antihypertensives.

Food-derived ACE-inhibitory peptides are far weaker than pharmaceutical ACE inhibitors, by orders of magnitude in potency terms. The interest in them was never that they might replace those drugs but that dietary intake might contribute a modest blood-pressure-lowering effect across a population.

IRW has the most characterization of the three. Beyond ACE inhibition, research has described effects on vascular endothelial function, including influences on nitric oxide signalling and inflammatory markers in vessel tissue, and reported reductions in blood pressure in spontaneously hypertensive rats.

It is worth noting that ACE has other substrates too — including Ac-SDKP, the anti-fibrotic tetrapeptide — so ACE inhibition has consequences beyond angiotensin.

The problem these peptides create for themselves

There is an unavoidable tension in this field, and it deserves stating plainly.

These peptides are produced by digestion. That is how they are generated in the first place. But the same digestive environment that releases them continues to act on them: gastrointestinal peptidases break tripeptides down further, and the intestinal brush border is rich in enzymes that degrade small peptides specifically.

So the question is not whether the peptide is active in a test tube — that is established — but whether meaningful quantities survive to reach the bloodstream and then the target tissue. Some short peptides do cross intact via peptide transporters, and proline-containing sequences such as LRP and LQP tend to resist certain peptidases better. But the fraction absorbed intact is generally small, and this is the limiting factor for the whole category.

The evidence base is also weighted heavily toward animal models and in vitro work. Human clinical trials of these specific tripeptides are limited, and the broader functional-food literature on peptide blood pressure effects has produced results that are real but modest, with meta-analyses generally showing small reductions.

What this means practically

These peptides are not approved therapies and are not established compounding substances. Where they appear commercially it is generally as functional food ingredients or supplements rather than as pharmaceutical products.

The honest framing for a patient is unusual in this formulary in being reassuring about safety and skeptical about need. These are components of ordinary food, produced by ordinary digestion, at exposures humans have always had. There is no meaningful safety concern in eating eggs or whole grains.

Whether isolating and supplementing them adds anything beyond eating the foods is not established, and the modest effect sizes in the wider literature suggest the ceiling is low. For a patient concerned about blood pressure, the interventions with substantial outcome evidence — dietary pattern, sodium reduction, weight management, physical activity, and pharmacotherapy where indicated — are where the effect actually lives.

Our peptide formulary lists each of these agents with its current status.