Immune-Modulatory Effects of Bioactive Collagen Peptides Improve Skin Health in Middle-Aged Women

Abstract

Introduction

Collagen peptides are widely used to support skin health, but the immunological mechanisms mediating such effects remain unclear. So, this study investigated the effects of bioactive collagen peptide (BCP) supplementation on facial wrinkles, skin biophysical properties, and systemic levels of transforming growth factor-beta (TGF-β) and Klotho in sedentary middle-aged women.

Methods

This randomized controlled trial included 119 healthy, sedentary women, aged 35–55 years who were randomly assigned to control, Col 2.5 g, or Col 10 g groups. Daily oral supplementation for 12 weeks consisted of either 2.5 g/day or 10 g/day of BCP (Peptpure^®), or participants were allocated to a non-supplemented control group.

Results

Supplementation with 10 g/day of BCP significantly reduced the number (p < 0.0002) and length (p < 0.0424) of wrinkles. Both collagen groups improved skin elasticity (p < 0.0321 for 2.5 g; p < 0.0065 for 10 g) and hydration (p < 0.0471 for 2.5 g; p < 0.0037 for 10 g). Plasma TGF-β levels were significantly elevated in the 2.5 g group (p < 0.0026) and 10 g group (p < 0.0001) compared with controls, as well as Klotho levels for both collagen groups (p < 0.0016 and p < 0.0001, respectively).

Conclusions

A 12-week course of Peptpure^® BCP supplementation improved facial skin health, underlined by increased systemic levels of TGF-β and Klotho, suggesting activation of regenerative and antiaging pathways.

Trial Registration

ClinicalTrials.gov identifier: NCT06971029.

Key Summary Points

Bioactive collagen peptide (Peptpure®) supplementation over 12 weeks resulted in improved wrinkles, elasticity, and hydration.

Bioactive collagen peptide (Peptpure®) supplementation increases TGF-β following skin improvement.

The beneficial effects of bioactive collagen peptide (Peptpure®) supplementation are mediated by increased Klotho, suggesting antiaging effects.

Bioactive collagen peptides (Peptpure®) support skin rejuvenation and modulate systemic biomarkers involved in regeneration and healthy aging, reinforcing its potential as an aesthetic nutraceutical.

Introduction

The global collagen market has grown substantially in recent years, mainly driven by consumer demand for health-promoting and aesthetic-enhancing products [1]. Among collagen-based products, hydrolyzed collagen and bioactive collagen peptides (BCPs) have gained particular attention owing to their high bioavailability and proven efficacy in promoting skin health [2, 3]. Clinical evidence indicates that BCP supplementation improves skin elasticity and hydration and reduces wrinkle formation, all key factors in skin aging [4]. Collectively, these findings support the expansion of the collagen market, underpinned by scientific evidence of multifunctional benefits in health, aesthetics, and industry.

Native collagen exists primarily as fibrillar proteins, with type I being the most abundant in skin, tendon, and bone, followed by type III, found with type I in extensible connective tissues such as skin, lungs, and vessels [5]. These forms are defined by a triple-helix structure conferring strength and enzymatic resistance [6, 7]. Hydrolyzed collagen, or gelatin, is produced by thermal or enzymatic hydrolysis of native collagen, breaking the helix into smaller polypeptides of 3–10 kDa [2–4]. Further enzymatic processing yields collagen peptides, shorter bioactive sequences under 3 kDa, which are absorbed directly in the gut and transported systemically, where they may stimulate extracellular matrix synthesis in skin, cartilage, and bone [2–4]. These BCPs differ not only in size but also in functional role, as they exert signaling properties and stimulate fibroblast activity, unlike native collagen and gelatin, limited by higher molecular weight and lower bioavailability [2, 3, 8, 9].

However, large studies investigating the immunological mechanisms underlying BCP effects on skin health in middle-aged women remain scarce and constitute the goal of the present clinical trial.

Methods

This study was approved by the Ethics Committee of the Evangelical University of Goiás (UniEVANGÉLICA), registration no. 7.233.377, and conducted in accordance with the Declaration of Helsinki. It was retrospectively registered at ClinicalTrials.gov (NCT06971029) on 13 May 2025 (https://clinicaltrials.gov/study/NCT06971029). The randomized controlled trial followed the Consolidated Standards of Reporting Trials (CONSORT) guidelines to ensure transparency and rigor. All recommendations from the CONSORT 2025 statement were addressed, and a flow diagram depicting enrollment, allocation, follow-up, and analysis is shown in Fig. 1. Additionally, we clarify that at the time of enrollment, collagen peptides were classified as food supplements under Brazilian regulatory standards, and prospective public registration was not mandatory. No modifications to the study design, primary outcomes, dosage, or statistical plan were made after participant inclusion, and data collection was completed prior to registration. Registration was performed later to ensure international transparency and conformity with CONSORT/International Committee of Medical Journal Editors (ICMJE) recommendations.

Fig. 1.

CONSORT study flow diagram

Patients’ rights to privacy were strictly observed throughout the study. No identifying information, including names, initials, hospital numbers, or images, was published in any form. The authors ensured that all participants were informed about the extent of the data shared and the potential for public access to identifiable material. In addition, all patients provided verbal and signed informed consent to participate in the study.

Recruitment and Eligibility

Women aged 35–55 years were recruited via social media, local radio, and UniEVANGÉLICA’s communication channels. Eligible participants were sedentary for at least 1 year and signed informed consent. Exclusion criteria included recent facial aesthetic procedures, use of skin-repairing cosmetics, protein/amino acid supplements, or smoking in the last 3 years.

Study Design and Intervention

A total of 119 volunteers meeting the inclusion and exclusion criteria were randomized. Five participants discontinued the study after randomization, resulting in 114 completers: control (n = 31; no supplementation), Col 2.5 (n = 42; 2.5 g/day), and Col 10 (n = 41; 10 g/day). Randomization was computer-generated, stratified by age, and implemented using opaque, sealed envelopes. Volunteers and researchers involved in the randomization of the volunteers were blinded to group allocation. Daily oral supplementation lasted 12 weeks. Peptpure^® BCP was provided by Peptech^® (São Paulo, Brazil). A placebo arm was not included in the present trial, as the primary objective was to explore dose–response effects and systemic biomarker modulation associated with bioactive collagen peptide supplementation. This design was chosen to provide mechanistic insights while minimizing participant burden. In addition, no formal priori power analysis was performed because the trial was originally designed as an exploratory academic investigation. Recruitment therefore included all eligible volunteers available during the enrollment window. The final sample of 114 completers provides adequate statistical power for detecting moderate effect sizes in continuous outcomes. Post hoc estimates based on the primary wrinkle endpoints indicate statistical power > 80% at α = 0.05. Future studies will incorporate prospective sample-size determinations aligned with minimally important clinical differences.

Amino Acid Profiling (High-Performance Liquid Chromatography–Tandem Mass Spectrometry [HPLC/MS–MS])

Samples (5 mg/mL) were acid-hydrolyzed (6N HCl, 110 °C, 24 h), neutralized, filtered (0.22 µm), and frozen. HPLC used a Zorbax Eclipse AAA column with formic acid in water/acetonitrile. Detection employed a Thermo Q Exactive Plus Orbitrap MS in positive mode with MRM for glycine, proline, hydroxyproline, alanine, and others. Standards (Sigma-Aldrich) ranged from 0.1 to 100 µM. Data were analyzed with Analyst^® or Xcalibur^® software [10].

Molecular Weight Distribution (Size-Exclusion Chromatography [SEC]–HPLC)

Molecular weight (MW) distribution was analyzed using SEC-HPLC (GB 31645-2018) on a TSKgel G2000 SWXL column at 30 °C with 30% acetonitrile/0.1% TFA. Detection occurred at 214 nm. Standards included cytochrome c, aprotinin, bacitracin, Gly–Gly–Tyr–Arg, and Gly–Gly–Gly. Results were expressed as peptide percentages within MW ranges [11].

Physicochemical and Microbiological Analyses

Assays included viscosity (GMIA Mod), pH, moisture (IT-PS.LAB.01–16), protein (Kjeldahl; ISO 1871:2009), solubility (IT-04), and bulk density (IT-POP-QUA-01). Visual inspection was performed. Heavy metals (Pb, As, Cd, Hg, Cr, Cu, and Zn) were measured using Association of Official Analytical Collaboration (AOAC) method 993.14 by atomic absorption. Microbiological testing followed AOAC methods: 990.12 (aerobes), 991.14 (E. coli), 2014.01 (Salmonella), 997.02 (yeasts/molds) [12–17].

Participant Characterization

Baseline data included age, Fitzpatrick skin phototype, weight, height, body mass index (BMI), fat and lean mass, hormone therapy, and supplement use (Table 1).

Table 1.

Characteristics of volunteers pre- and post-3-month bioactive collagen peptide supplementation

	Control pre	Control post	p-Value	Col 2.5 g pre	Col 2.5 g post	p-Value	Col 10 g pre	Col 10 g post	p-Value
	n = 31			n = 42			n = 41
Age (years)	45.95 ± 6.59		ns	46.29 ± 6.25		ns	44.12 ± 7.37		ns
Fitzpatrick I	0 0 13 16 4		ns	0 1 17 21 4		ns	0 0 22 17 2		ns
Fitzpatrick II			ns			ns			ns
Fitzpatrick III			ns			ns			ns
Fitzpatrick IV			ns			ns			ns
Fitzpatrick V			ns			ns			ns
Body weight (kg)	73.81 ± 15.75	70.31 ± 11.41	ns	71.57 ± 12.90	74.46 ± 13.02	ns	71.48 ± 13.33	39.92 ± 12.81	ns
Height (m)	1.61 ± 0.06		ns	1.62 ± 0.04		ns	1.59 ± 0.05		ns
Body mass index (kg/m2)	27.38 ± 7.76	26.55 ± 4.01	ns	27.35 ± 4.02	27.82 ± 3.97	ns	28.52 ± 5.19	27.75 ± 5.17	ns
Body fat (%)	38.69 ± 0.07	36.91 ± 0.06	ns	39.95 ± 0.06	38.64 ± 0.08	ns	40.64 ± 0.06	37.66 ± 0.09	ns
Lean mass (%)	26.24 ± 0.03	26.93 ± 0.02	ns	25.76 ± 0.03	26.43 ± 0.03	ns	25.50 ± 0.04	27.57 ± 0.08	ns
Dyslipidemia	2		ns	1		ns	4		ns
Diabetes	1		ns	2		ns	2		ns
Systemic arterial hypertension	4		ns	1		ns	5		ns
Hormone replacement	7		ns	9		ns	6		ns
Dietary supplement	12		ns	17		ns	14		ns

kg, kilogram; m, meters; kg/m², kilogram/square meter; %, percentage; ns, not significant

Skin Elasticity, Hydration, and Oiliness Analysis

Parameters were measured using Doctor Skin^® analyzer with bioimpedance under controlled conditions (22–24 °C; 45–55% relative humidity [RH]). Participants avoided topical products for 12 h before testing. Measurements at the periorbital region were averaged from three readings. Results included hydration, oil percentage, and elasticity index [18].

Quantitative Analysis of Wrinkles

Wrinkle analysis was performed using Image-Pro Plus version 4.5 (Media Cybernetics, MD, USA). All wrinkle images were coded with anonymized identification numbers generated at randomization, and the investigator responsible for wrinkle quantification remained blinded to group allocation and supplementation dose during image processing and analysis. The total area ensured scale consistency, and a periorbicular region of interest (ROI) was manually delineated. Within this ROI, visible wrinkles were identified and counted, and the length measured in micrometers (µm).

Data Processing and Statistical Analysis for Wrinkles

For each participant, wrinkle counts and total length were calculated by summing right and left images. Primary outcomes were number and total wrinkle length. Pre- versus postintervention comparisons used paired t-tests. Significance was set at p < 0.05. Analyses were run in GraphPad Prism version 8.0.2.

Plasma Levels of Transforming Growth Factor-Beta (TGF-β) and Klotho

Blood was collected in EDTA tubes and centrifuged (900g, 7 min, 4 °C), and plasma was stored at −80 °C. Enzyme-linked immunosorbent assay (ELISA) kits (R&D Systems) measured TGF-β (DY240) and Klotho (DY5334-05). Readings used a Spectramax I3 microplate reader [19, 20].

Statistical Analysis

Data were analyzed with GraphPad Prism version 8.0.2. Normality was tested by Shapiro–Wilk. Baseline comparisons used one-way analysis of variance (ANOVA). Postintervention analyses employed analysis of covariance (ANCOVA) adjusted for baseline values, followed by Tukey’s post hoc. Significance was p < 0.05. Results are shown as scatter plots of individual values.

Results

Product Characterization

Amino Acids Profile of BCPs by HPLC/MS–MS

Analysis of the BCPs revealed predominance of glycine (23.6 g/100 g protein), proline (13.9 g/100 g), hydroxyproline (11.6 g/100 g), and alanine (8.1 g/100 g). These collagen-specific amino acids were the major constituents. Moderate levels of glutamic acid (9.2 g/100 g) and arginine (7.68 g/100 g) were also found. Lower levels included aspartic acid (5.19 g/100 g), lysine (4.2 g/100 g), serine (3.01 g/100 g), and leucine (2.84 g/100 g). Essential amino acids such as threonine (2.05 g/100 g), isoleucine (1.52 g/100 g), phenylalanine (1.88 g/100 g), methionine (0.83 g/100 g), valine (2.16 g/100 g), and histidine (0.63 g/100 g) were detected in smaller amounts. Cystine was minimal (0.01 g/100 g). This profile confirms the expected collagen peptide signature.

Molecular Weight Distribution of BCPs by HPLC

The molecular weight distribution showed peptides mainly between 5000 Da and 3000 Da (30.55%), followed by 1000–500 Da (20.77%) and 2000–1000 Da (14.78%). Fractions of 500–180 Da and 3000–2000 Da accounted for 14.61% and 12.36%, respectively. Smaller proportions were < 180 Da (4.61%) or > 10,000 Da (2.33%). No peptides were detected between 5000 Da and 10,000 Da. The mean molecular weight was 1715 Da, indicating high digestibility, bioavailability, and hypoallergenic potential.

Characteristics of the Volunteers

Table 1 summarizes baseline and postintervention characteristics across groups (control, Col 2.5, and Col 10). No significant differences were found in age, height, or phototype. Baseline age ranged from 44.12 ± 7.37 years to 46.29 ± 6.25 years, and height from 1.59 ± 0.05 m to 1.62 ± 0.04 m. Body weight, BMI, fat percentage, and lean mass showed no significant changes after supplementation (p > 0.05). Slight, nonsignificant reductions in fat percentage were noted in collagen groups (e.g., 39.95–38.64% in Col 2.5; 40.64–37.66% in Col 10), with modest increases in lean mass, especially in Col 10 (25.50% to 27.57%). Clinical variables (dyslipidemia, diabetes, hypertension, hormone therapy, and supplement use) remained unchanged. Thus, 3 months of collagen supplementation did not significantly affect general, anthropometric, or clinical parameters.

Study Flow Diagram

Figure 1 displays the CONSORT flow diagram.

Primary Outcomes

Number and Length of Wrinkles

Figure 2A shows wrinkle number: Only the Col 10 group exhibited a significant reduction postintervention versus baseline (p < 0.0002; 95% confidence interval [CI] 0.3923–1.108). Control and Col 2.5 showed no significant changes. Figure 2B shows wrinkle length: Both Col 2.5 and Col 10 groups had significant reductions postintervention (p < 0.0475; 95% CI 527.7–11,950; p < 0.0424; 95% CI 3949–22,920, respectively), while the control group did not.

Fig. 2.

Effects of hydrolyzed collagen peptide supplementation on wrinkle number and length in middle-aged women. A Number of facial wrinkles and B total wrinkle length (µm) was assessed before (pre) and after (post) a 12-week intervention in control and collagen peptide groups (2.5 g/day and 10 g/day). Data are presented as individual values with scatter plot. Statistical comparisons were conducted among all groups. A p-value ≤ was considered significant

Secondary Biochemical Outcomes

Skin Elasticity, Hydration, and Oiliness

Figure 3A shows elasticity: Significant increases were observed in Col 2.5 (p < 0.0321; 95% CI −0.2795 to −0.01316) and Col 10 (p < 0.0065; 95% CI −0.2981 to −0.05191), but not in the control. Figure 3B shows hydration: Both Col 2.5 (p < 0.0471; 95% CI 0.06248–9.428) and Col 10 (p < 0.0037; 95% CI 5.293–22.07) improved significantly, with no changes in the control. No group differences were seen in oiliness. These findings indicate that collagen peptides improved biomechanical and moisture-retention properties, with greater benefits at a higher dose.

Fig. 3.

Effects of hydrolyzed collagen peptide supplementation on skin elasticity and hydration in middle-aged women. A Skin elasticity index and B skin hydration (%) were measured before (pre) and after (post) a 12-week supplementation period in the control group and collagen peptide groups (2.5 g/day and 10 g/day). Data are presented as individual values with scatter plot. Statistical comparisons were conducted among all groups. A p value ≤ was considered significant

Biomarker Outcomes

Plasma Levels of TGF-β and Klotho

Figure 4 shows plasma TGF-β (A) and Klotho (B). TGF-β did not change in the control, but both collagen groups showed higher levels versus control post: Col 2.5 (p < 0.0026; 95% CI −14.07 to −3.292) and Col 10 (p < 0.0001; 95% CI −28.20 to −12.26), indicating dose-dependence. Klotho levels also rose significantly in collagen groups versus the control post group: Col 2.5 (p < 0.0016; 95% CI −14.07 to −3.292) and Col 10 (p < 0.0001; 95% CI −123.7 to −44.77). Together, these results suggest that collagen supplementation modulates systemic biomarkers of tissue remodeling and aging in a dose-dependent manner.

Fig. 4.

Effects of hydrolyzed collagen peptide supplementation on circulating levels of TGF-β and Klotho in middle-aged women. A Plasma levels of transforming growth factor-beta (TGF-β) and B plasma levels of Klotho were measured before (pre) and after (post) 12 weeks of supplementation with hydrolyzed collagen peptides at doses of 2.5 g/day and 10 g/day, compared with a control group. Data are presented as individual values with scatter plot. Statistical comparisons were conducted among all groups. A p value ≤ was considered significant

Discussion

This randomized, controlled clinical trial investigated the effects of bioactive collagen peptide (BCP) supplementation on facial wrinkles, skin biophysical properties, and systemic biomarkers of tissue remodeling and aging, such as TGF-β and Klotho in middle-aged women. Our findings demonstrate that 12 weeks of daily BCP supplementation, particularly at a dose of 10 g/day, lead to significant improvements in wrinkle count and length, skin elasticity and hydration, and increased plasma levels of TGF-β and Klotho, suggesting not only aesthetic but also systemic benefits of BCP supplementation through immunoregulatory pathways.

The observed improvements in skin elasticity and hydration align with previous evidence supporting the efficacy of BCP in enhancing skin mechanical and barrier properties. Clinical trials, systematic reviews, and meta-analyses have shown that collagen peptides stimulate dermal fibroblast activity, promoting the synthesis of extracellular matrix (ECM) components such as collagen and elastin, which improve skin elasticity and moisture retention [3, 4, 21]. The results from the current study reinforce these outcomes, particularly by demonstrating dose-responsiveness, with greater effects seen at the 10 g/day dose compared with 2.5 g/day, consistent with previous dose-dependent findings [22]. Our biochemical characterization of BCP confirmed its richness in glycine, proline, hydroxyproline, and alanine amino acids known for their specific roles in collagen fiber formation and fibroblast signaling [2–6]. These amino acids, particularly hydroxyproline and proline, have been implicated in activating dermal fibroblasts and upregulating genes involved in ECM remodeling, such as COL1A1 and elastin [8, 23]. Moreover, the molecular weight profile (predominantly peptides < 3000 Da) indicates high bioavailability, allowing systemic absorption and potential immunological-like effects beyond local dermal remodeling, which is being investigated by other studies as well [24].

Notably, this study is one of the first to assess the systemic immunological effects of collagen peptides in middle-aged women by evaluating plasma TGF-β and Klotho levels. TGF-β is a well-characterized anti-inflammatory cytokine from growth factor family that also regulates fibroblast proliferation and ECM deposition [25]. The increased TGF-β levels in the collagen-supplemented groups suggest that BCP may induce a systemic anti-inflammatory or proregenerative milieu, supporting its role in skin regeneration and possibly other tissues. This is in line with findings from in vitro and animal models where collagen peptides have stimulated TGF-β production and modulated inflammatory responses [2, 7, 25]. Even more novel is the finding that BCP supplementation significantly elevated plasma Klotho levels. Klotho is an antiaging protein involved in antioxidative defense, ECM homeostasis, and suppression of fibrosis [26]. Low levels of Klotho are associated with aging and age-related diseases [27, 28]. Although the mechanisms by which BCP modulate Klotho remain to be fully elucidated, the increase observed herein may reflect an indirect systemic benefit through improved ECM balance or gut–skin axis modulation, as BCPs are known to influence gut microbiota and systemic oxidative status [29].Together, these findings suggest a possible synergistic mechanism where BCP supplementation not only provides structural amino acids but also induces systemic antiaging pathways, evidenced by elevated TGF-β and Klotho. Such dual action may underline the superior clinical outcomes observed in the high-dose group. These findings broaden the current understanding of the impact of collagen peptides, supporting their therapeutic potential beyond cosmetic improvement to include healthy aging and systemic immunomodulation.

Despite these promising findings, some limitations should be acknowledged. The study was limited to sedentary middle-aged women and did not explore long-term effects beyond 12 weeks. The absence of a placebo group may have influenced the perception of some subjective outcomes. First, although the trial included a randomized non-supplemented control group, the absence of a placebo control may limit the strength of causal inference and does not fully exclude expectancy effects. However, the primary outcomes were based on objective instrumental and image-based assessments of skin properties, and the observed dose-dependent improvements across multiple endpoints, together with concomitant increases in systemic biomarkers such as TGF-β and Klotho, support a biological effect of bioactive collagen peptide supplementation. Nevertheless, future studies using double-blind, placebo-controlled designs are warranted to further confirm these findings and to strengthen clinical translation. Furthermore, mechanistic insights into how BCP affects Klotho expression require further molecular studies. Future trials should investigate whether these systemic changes translate into clinically meaningful improvements in aging-related conditions or other organs.

Conclusions

Hydrolyzed collagen peptide supplementation significantly improves facial wrinkle parameters and skin biophysical properties in a dose-dependent manner, while also increasing systemic levels of TGF-β and Klotho. These findings provide new insights into the immunological and antiaging mechanisms of collagen supplementation, supporting its role not only in aesthetic enhancement but also as a nutraceutical strategy to promote healthy aging.

Author Contributions

Methodology, formal analysis and investigation: Rosa Helena Ramos Paula-Vieira, Sandra Regina Dias, Anamei Silva-Reis, Meiry Souza Moura-Maia, Nycole Vieira Ramos-Gomes, Kananda Jesus-Silva, Yasmim Rodrigues Oliveira-Leal, Laura Thaís Castro-Pimentel, Wany Soares Fagundes Carvalho, Flavia Melo, José Luis Rodrigues Martins, and André Luis Lacerda Bachi; writing—original draft preparation, funding acquisition, resources, and supervision: Rodolfo P. Vieira. All authors met the ICMJE criteria as follows: RHRPV, SRD, ASR, MSMM, NVRG, KJS, YROL, LTCP, WSFC, FM, JLRM, and ALLB made significant contributions to investigation, methodology, and visualization. RPV made significant contributions to conceptualization, formal analysis, writing—original draft, project administration, methodology, investigation, funding acquisition, resources, visualization, validation, data curation, and supervision.

Funding

We thank Sao Paulo Research Foundation (FAPESP) for the young investigator research grant no. 2012/15165-2 granted to Prof. Dr. Rodolfo P. Vieira. We thank Goias Research Foundation (FAPEG), for the PhD fellowship no. 202310267000648 granted to Anamei Silva-Reis. Neither FAPESP nor FAPEG had no role in the study design, analysis, interpretation, conclusions, and manuscript writing. The Rapid Service Fee was funded by the authors.

Data Availability

The raw data will be made available upon reasonable request to the corresponding author.

Declarations

Conflict of Interest

We thank the company Peptech^® for generously providing the bioactive collagen peptides (Peptpure^®) for this study. In addition, we state that Prof. Dr. Rodolfo P. Vieira has received consultation fees and Rosa Helena Ramos Paula-Vieira and Sandra Regina Dias a MSc fellowship from Peptech^®. Lastly, we clarify that Peptech^® had no role in the study design, analysis, interpretation, conclusions, and manuscript writing. Anamei Silva-Reis, Meiry Souza Moura-Maia, Nycole Vieira Ramos-Gomes, Kananda Jesus-Silva, Yasmim Rodrigues Oliveira-Leal, Laura Thaís Castro-Pimentel, Wany Soares Fagundes Carvalho, Flavia Melo, José Luis Rodrigues Martins, and André Luis Lacerda Bachi have nothing to disclose.

Ethical Approval

This study was approved by the Ethics Committee of the Evangelical University of Goiás (UniEVANGÉLICA), registration no. 7.233.377, and conducted in accordance with the Declaration of Helsinki. It was retrospectively registered at ClinicalTrials.gov (NCT06971029) on 13 May 2025 (https://clinicaltrials.gov/study/NCT06971029). The randomized controlled trial followed CONSORT guidelines to ensure transparency and rigor. All recommendations from the CONSORT 2025 statement were addressed, and a flow diagram depicting enrollment, allocation, follow-up, and analysis is shown in Fig. 1. Additionally, we clarify that at the time of enrollment, collagen peptides were classified as food supplements under Brazilian regulatory standards, and prospective public registration was not mandatory. No modifications to the study design, primary outcomes, dosage, or statistical plan were made after participant inclusion, and data collection was completed prior to registration. Registration was performed later to ensure international transparency and conformity with CONSORT/ICMJE recommendations. Patients’ rights to privacy were strictly observed throughout the study. No identifying information, including names, initials, hospital numbers, or images, was published in any form. The authors ensured that all participants were informed about the extent of the data shared and the potential for public access to identifiable material. In addition, all patients provided verbal and signed informed consent to participate in the study.