L-Proline

Proline

Snapshot

Indications	Contraindications
Hard-to-heal wounds¹ Oral mucositis pain²	Pregnancy or nursing³ Under age 18³

L-proline is an amino acid the body synthesizes from glutamine. Supplementation rests on its role as a collagen precursor, since amino acid supply is critical to wound repair⁴.

The wound evidence is small and confounded: a randomized trial of an oral nutritional supplement combining arginine and proline with vitamins and minerals reduced wound surface area, though the formula cannot isolate proline¹; a critical review describes biochemical barriers that limit enteral amino acid supplementation for wound repair⁴. In a 1987 study of healthy volunteers, proline taken with a high-nitrate meal raised urinary N-nitrosoproline, and vitamin C lowered it⁵. Products listing L-proline number 1,985 and come as powders, capsules, and tablets; see Form comparison.

No safe upper limit can be estimated without controlled trials, and the only proline supplementation study, in gyrate atrophy, reported no deleterious side effects⁶. The pregnancy and nursing warnings on US product labels are manufacturer precautions, not trial findings³. Per product labeling, kidney or liver disease prompts consultation with a health care practitioner rather than avoidance³.

Last updated October 17, 2026. Read how we make monographs.

In the full monograph

20 sources, 14 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources