Tier 3 — preclinical

Oral supplementation with specific bioactive collagen peptides improves nail growth and reduces symptoms of brittle nails

Doris Hexsel, Vivian Zague, Michael Schunck, Carolina Siega, Fernanda O. Camozzato, Steffen Oesser

Journal of Cosmetic Dermatology 2017 16(4):520–526

Bibliography

DOI: 10.1111/jocd.12393
PubMed: PMID 28786550
Funding: No funding statement is disclosed in the paper. The Verisol test product was supplied by Gelita AG (Eberbach, Germany).
Competing interests: No competing interests statement is disclosed in the paper.

Study snapshot

Design	Open-label, single-centre, single-arm interventional trial with 4-week off-therapy observation phase
Model	Adult Brazilian women aged 18–50 (mean 39.3) with clinical signs of brittle nail syndrome (lamellar peeling, edge irregularities, or longitudinal ridging)
Sample	n=25 enrolled, n=24 completed
Intervention	2.5 g/day Verisol bioactive collagen peptides (porcine type I, mean molecular weight ~2.0 kDa, Gelita AG, Eberbach, Germany), dissolved in water, once daily
Duration	24 weeks supplementation plus 4-week off-therapy observation
Endpoints	Nail growth rate (mm/month, measured from lunula edge on middle finger); frequency of cracked or chipped nails (participant daily log); brittle nail symptoms (peeling, edge irregularities, roughness) via Sherber grading system; global clinical improvement (5-point scale); participant satisfaction; adverse events

What the study showed, in plain terms

Researchers gave 25 Brazilian women aged 18 to 50 who had noticeably brittle nails a daily 2.5 g dose of a specific porcine collagen peptide product (Verisol) for 24 weeks, then observed them for another 4 weeks after stopping. All the women showed at least one classic brittle-nail sign at the start — peeling, ragged edges, or ridging. There was no placebo group; every participant received the collagen.

Nail growth rate increased by 12% by week 24, and the number of broken or chipped nails per month dropped by 42%. Almost two-thirds of the women showed a clear clinical improvement in nail appearance by week 24, and this rose to 88% four weeks after they stopped taking the supplement. Eighty percent said they were satisfied with the results. No side effects were reported.

These are encouraging signals for anyone with brittle nails, but the design of the trial — no placebo group and small sample — means the improvements can't be confidently attributed to the collagen alone. The authors themselves call for larger placebo-controlled trials before drawing firm conclusions.

Key findings

Nail growth rate improved from a baseline mean of 2.65 ± 0.42 mm/month to 2.90 ± 0.47 mm/month at week 12 (p<0.05) — a 10% increase — rising to 12% at week 24 and 15% at 4-week washout.
Frequency of cracked or chipped nails fell from a baseline mean of 10.5 ± 8.4 per month to 6.4 ± 4.9 per month at week 24 (p<0.05) — a 42% reduction — sustained during the washout phase.
64% of participants achieved global clinical improvement (excellent/good/fair) at week 24. This rose to 88% four weeks post-treatment, suggesting a lingering effect.
By week 24 only 25% of participants scored "severe" or "moderate" for lamellar peeling, versus 67% at baseline.
80% of participants reported being satisfied or very satisfied with the treatment; 75% perceived their nails as stronger; 71% felt their nails were growing faster.
No adverse events related to the study product were reported.

What this study can and cannot tell us

Open-label, single-arm, no placebo control. The observed improvements cannot be separated from placebo response, seasonal variation, behavioural changes (e.g. better nail care during the study), or natural fluctuation in brittle nail symptoms. This is the single most important limitation.
Very small sample (n=24 completers). Any confidence interval around the reported effect sizes would be wide.
Single-centre, single-sex, single-country (Brazilian women) design. Generalisability to men and to other populations is unproven.
Objective nail growth was measured on the middle finger only. Growth rates vary across fingers and this measurement may not represent whole-hand nail health.
Prominent outcomes are subjective (satisfaction, self-perceived nail strength) rather than blinded objective measurements.
Statistical analysis used one-way ANOVA with Fisher post-hoc, which is not the ideal choice for within-subject longitudinal data with correlated observations.
Undisclosed commercial ties: two authors are affiliated with a research entity closely linked to the Verisol manufacturer, and the formal COI declaration is absent from the published paper.
The authors explicitly state that larger placebo-controlled trials are required to confirm the observed results.

Tier 2

Oral Intake of Low-Molecular-Weight Collagen Peptide Improves Hydration, Elasticity, and Wrinkling in Human Skin: A Randomized, Double-Blind, Placebo-Controlled Study

Do-Un Kim et al. · Nutrients · 2018

Tier 4

Assessment of bioavailability after in vitro digestion and first pass metabolism of bioactive peptides from collagen hydrolysates

Christina E. Larder et al. · Current Issues in Molecular Biology · 2021