Collagen Peptides Show Sustained Skin Benefits 4 Weeks After Stopping
The most common hesitation around collagen supplementation isn’t whether it works. It’s what happens when you stop. A new clinical trial from Shanghai’s Fumei Medical Cosmetology Clinic offers the first structured answer to that question.
A randomized, double-blind, placebo-controlled trial enrolled 83 healthy women aged 35 to 55, with 77 completing the full protocol (39 treatment, 38 placebo). The treatment group took 5,000mg/day of bovine type I collagen peptides for 12 weeks, then stopped. Measurements were taken at baseline, weeks 4, 8, and 12, and crucially at week 16, four weeks after the last dose.
Hydration and Barrier Function
At week 16, the treatment group recorded mean moisture of 44.38% ± 7.62%, an average increase of 9.15% from baseline (p < 0.001). The placebo group showed no comparable gain.
Transepidermal water loss (TEWL), which measures how much moisture escapes through the skin barrier, told a sharper story. The treatment group saw TEWL fall 17.05% while the placebo group’s TEWL rose 3.07% over the same period. A lower TEWL means a stronger barrier. Four weeks after stopping supplementation, the improvement had not reversed.
Firmness and Dermal Density
Skin firmness (F4) improved 10.34% from baseline in the treatment group, and was 15.48% greater than placebo at week 16 (p < 0.0001).
Dermal density showed the steepest divergence. The treatment group gained 19.20% from baseline while the placebo group lost 7.13% over the same 16 weeks (p < 0.0001). Dermal thickness loss was also dramatically different: 1.27% in the treatment group versus 11.92% in placebo. A nearly tenfold difference over the same time window.
Why Effects Persist After Stopping
The collagen in this trial was enzymatically hydrolyzed, with hydroxyproline at 16.6% and 43% of peptides at or below 1,000 Da in molecular weight. Smaller fragments pass through the intestinal wall into circulation more readily.
Hydroxyproline-containing peptides are thought to act as signals for dermal fibroblasts, the cells that produce collagen. The proposed mechanism is that supplementation doesn’t just supply raw material but activates the skin’s own collagen synthesis, and that activation continues beyond the last dose.
What the 16-Week Design Shows
Most collagen trials end when supplementation ends. This trial’s washout window is the differentiating variable. Hydration (p < 0.001), firmness (p < 0.0001), and dermal density (p < 0.0001) all held statistical significance at week 16. No adverse reactions were reported.
The 5,000mg/day dose is a well-studied threshold in this category. Vitamin C is a cofactor in collagen synthesis, so existing routines that include it may reinforce similar outcomes. The washout data also raises a practical question: whether cyclical supplementation delivers comparable results to continuous daily use.
Sources
Shanghai Fumei Medical Cosmetology Clinic, Randomized Double-Blind Placebo-Controlled Trial on Bioactive Collagen Peptides. PMC.