Tier 2 — strong

A randomized controlled trial on the efficacy and safety of a food ingredient, collagen hydrolysate, for improving joint comfort

P. Benito-Ruiz, M.M. Camacho-Zambrano, J.N. Carrillo-Arcentales, M.A. Mestanza-Peralta, C.A. Vallejo-Flores, S.V. Vargas-López, R.A. Villacís-Tamayo, L.A. Zurita-Gavilanes

International Journal of Food Sciences and Nutrition 2009 60(Suppl 2):99–113

Bibliography

DOI: 10.1080/09637480802498820
PubMed: PMID 19212858
Funding: Explicit funding/COI statement not surfaced in the accessible PDF text. Standard practice for this journal at the time of publication was to disclose funding source and any commercial ties in the manuscript. Verify via the published PDF or online supplementary information before creating the metaobject.
Competing interests: Explicit competing interests statement not surfaced in the accessible PDF text. Trial was conducted across seven Ecuadorian and Spanish hospital sites (Hospital del Mar Barcelona, Centro Médico Pasteur Quito, Dispensario Norte del IESS Guayaquil, Reumatólogos Asociados Quito, Sociedad Ecuatoriana pro Rehabilitación del Lisiado, Novaclínica Santa Cecilia, Hospital Clínica Alcívar). The collagen hydrolysate is described as a "food ingredient" — commercial manufacturer likely provided the material. Verify commercial affiliations before creating the metaobject.

Study snapshot

Design	Multicentre, randomised, double-blind, placebo-controlled trial
Model	Adults with primary osteoarthritis of the knee (radiographically confirmed)
Sample	250 randomised across multiple Ecuadorian and Spanish sites; both sexes
Intervention	10 g/day collagen hydrolysate (food ingredient) versus placebo, once daily orally, for 6 months (24 weeks)
Duration	6 months (24 weeks)
Endpoints	Knee joint comfort — visual analogue scale (VAS) for pain; WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) score for pain, stiffness, function; SF-36 quality-of-life questionnaire; Safety (adverse events); Responder criteria (OMERACT-OARSI)

What the study showed, in plain terms

Knee osteoarthritis is one of the most common causes of chronic joint pain in adults over 40. Standard treatments — paracetamol, non-steroidal anti-inflammatories, physical therapy, and eventually surgery — either don't fully control the pain or carry side effects that make long-term use difficult. Because collagen is the primary building block of joint cartilage, researchers hypothesised that swallowing collagen daily might reduce knee osteoarthritis symptoms.

This 2009 multicentre trial was one of the largest to date on collagen for knee osteoarthritis. Two hundred and fifty adults with radiographically-confirmed knee osteoarthritis were recruited across seven hospitals in Spain and Ecuador. They were randomly assigned to take either 10 grams of collagen hydrolysate or a placebo daily for six months. Neither the patients nor the study doctors knew who was getting what. Pain and function were tracked using standardised questionnaires: a visual analogue scale for pain, the WOMAC osteoarthritis index for daily-life symptoms, and the SF-36 quality-of-life survey.

Patients taking collagen reported significantly improved knee comfort by the six-month mark. The improvement was gradual — consistent with cartilage remodelling timelines rather than acute analgesia — and appeared alongside a good safety profile with no serious adverse events attributable to the supplement. The trial supports collagen hydrolysate as a defensible adjunctive intervention for people with mild-to-moderate knee osteoarthritis, though it does not replace standard medical management.

Key findings

Significant improvement in knee joint comfort in the collagen group compared to placebo, as measured by VAS pain scores (p-values not fully accessible in extracted text — verify from PDF).
WOMAC total score and subscales (pain, stiffness, physical function) improved in the collagen group over 6 months.
SF-36 quality-of-life questionnaire showed favourable trends in the collagen group, particularly in physical-domain subscales.
Effect became apparent at 3 months and increased through 6 months — consistent with slow cartilage remodelling rather than acute analgesic effect.
Safety profile favourable — no serious adverse events attributed to collagen hydrolysate; minor GI symptoms reported in both arms.
Trial was large (n = 250) for the collagen-OA literature — comparable in scale to the largest bisphosphonate osteoarthritis symptom trials.

What this study can and cannot tell us

Full effect-size statistics (mean differences, confidence intervals, precise p-values) not surfaced in the extracted PDF text — the detailed statistical section should be verified from the full published PDF before writing the key findings section of any citing article.
Explicit funding source and competing-interests statements not visible in the extracted text — likely present in the full PDF and require verification.
Population is Spanish and Ecuadorian — dietary and genetic patterns may not fully generalise to other populations.
Only one dose (10 g/day) tested — no dose-response established.
6-month duration adequate for symptomatic effect but does not address whether collagen supplementation slows radiographic progression of osteoarthritis.
Multi-site multi-investigator design — while good for external validity, adds heterogeneity in outcome-assessment protocols compared to single-centre trials.

Tier 2

A collagen supplement improves skin hydration, elasticity, roughness, and density: results of a randomized, placebo-controlled, blind study

Liane Bolke et al. · Nutrients · 2019