Benefits
Endurance running distance alongside a training program
In two placebo-controlled trials of 15 g a day for 12 weeks, adults doing combined running and strength training ran farther in a one-hour time trial than the placebo group: 1727 versus 1018 m more in 32 men and 1034 versus 703 m more in 59 women. Both groups trained, the placebo contained no protein, and GELITA part-funded both trials.
Running speed at the lactate and anaerobic thresholds
In the men's trial, running speed at the lactate threshold rose 0.68 km/h on collagen and fell 0.135 km/h on placebo, and speed at the individual anaerobic threshold rose 1.66 versus 0.606 km/h. In the women's trial both speeds improved in both groups with no difference between them, although heart rate at the anaerobic threshold fell 8 versus 1 beats a minute.
Strength and jump recovery after muscle-damaging exercise
In 55 mostly sedentary men who took a blend of 10 g PeptENDURE and 5 g TENDOFORTE a day for 12 weeks with combined training, maximal strength, rate of force development and jump height recovered faster after 150 drop jumps than on placebo, and blood markers of muscle damage rose less. Soreness did not differ. The blend design means the result cannot be credited to PeptENDURE alone.
Body composition during combined training
Results on body composition did not line up across the three trials. In women, fat-free mass rose 0.8 kg on collagen versus 0.3 kg on placebo, while fat mass fell in both groups without a difference. In men, neither fat mass nor fat-free mass differed between groups, and in the blend trial no body composition measure differed from placebo.
Mechanism of action
Mitochondrial density: a maker claim from animal work
GELITA says preclinical models showed higher mitochondrial density in muscle. The men's trial paper cites a 2019 University of Lübeck thesis, not published in a journal, in which rats given specific collagen peptides for 4 weeks showed higher mitochondrial density by electron microscopy; GELITA has not said which studies its own claim rests on. No published human trial of PeptENDURE has measured mitochondria, muscle enzymes or VO2max, so this remains an untested idea in people.
Extra protein compared with a protein-free placebo
All three trials compared 15 g of collagen with silicon dioxide, which supplies no protein. The extra protein itself may explain part of the gain: a meta-analysis of 19 trials found that protein supplements during endurance training improved time trial performance, while a review of concurrent training found no added rise in VO2max.
Connective tissue remodeling around muscle
The blend trial authors propose that longer-term collagen peptide intake may support remodeling of the extracellular matrix around muscle fibers, which could help force production after damaging exercise. The trial did not measure the matrix directly, so this is the authors' hypothesis.
Clinical trials
Double-blind, placebo-controlled randomized trial of 15 g a day of PeptENDURE (named in the full text, from GELITA) or silicon dioxide placebo for 12 weeks, alongside 60 minutes of moderate running and 15 minutes of resistance training per session. The primary endpoint was distance covered in a 1-hour time trial. The registry also lists leg strength, waist circumference and blood lipids as secondary outcomes, which the paper does not report. Registered retrospectively as DRKS00015529. The paper states the research was in part funded by GELITA Health GmbH, while the registry entry lists no external funding; no author lists a GELITA affiliation. (Jerger et al. 2023, Sports Med Open)
50 moderately trained men aged 18 to 40 were recruited. 18 dropped out for missed sessions, illness or injury, none for side effects, and 32 (15 collagen, 17 placebo), average age about 28, were analyzed per protocol.
Time trial distance, the primary endpoint, rose 1727 m on collagen versus 1018 m on placebo, a significant group difference (p ≤ 0.05). Running speed rose more on collagen at the lactate threshold (0.68 km/h versus a 0.135 km/h fall) and at the individual anaerobic threshold (1.66 versus 0.606 km/h). Fat mass and fat-free mass changes did not differ between groups. VO2max and muscle mitochondria were not reported.
Double-blind, placebo-controlled randomized trial of 15 g a day of specific collagen peptides from GELITA, which the paper's funding note says will be named PeptENDURE, or silicon dioxide placebo for 12 weeks with combined running and strength training 3 days a week. The paper names no single primary outcome; its registry entry (DRKS00020534, registered retrospectively) names the 1-hour time trial, lists a target and final sample of 140, and describes a second arm with endurance training only, which the paper does not report. The paper states it was in part funded by GELITA GmbH, while the registry lists no external funding. (Jendricke et al. 2020, Front Nutr)
Recreationally active women aged 18 to 40 who ran regularly. 90 were recruited, 31 dropped out for reasons other than side effects, and 59 (28 collagen, 31 placebo) were analyzed per protocol.
Running distance in the 1-hour time trial rose 1034 m on collagen versus 703 m on placebo (interaction p < 0.05). Running speed at the lactate and anaerobic thresholds improved in both groups without a group difference, while heart rate at the anaerobic threshold fell 8 versus 1 beats a minute (p < 0.01). Fat-free mass rose 0.8 versus 0.3 kg (p < 0.05). Fat mass, one-repetition maximum and muscular endurance did not differ between groups.
Double-blind, placebo-controlled randomized trial of 15 g a day made up of 10 g PeptENDURE and 5 g TENDOFORTE, or silicon dioxide placebo, for 12 weeks of combined resistance and endurance training 3 times a week, with 150 drop jumps before and after to induce muscle damage. GELITA supplied the products and placebo and funded the study; one author is at the Collagen Research Institute in Kiel, which the registry (NCT05220371) lists as an industry collaborator. The registry lists ten primary outcomes, including soreness and body composition. A companion paper reports blood markers from the same trial. (Bischof et al. 2023, Front Nutr)
75 predominantly sedentary men aged 18 to 40 were randomized (37 collagen, 38 placebo) and 55 (26 and 29) were analyzed per protocol. The registry records an actual enrollment of 50. No adverse events related to either product were recorded.
After 12 weeks, maximal voluntary contraction (p = 0.02), rate of force development (p < 0.01), peak rate of force development (p < 0.01) and jump height (p = 0.046) recovered faster after the drop jumps on collagen. Muscle soreness (p = 0.66) and body composition did not differ, and both are registered primary outcomes. In the companion paper, which analyzed only the men with complete blood samples (about 21 to 23 per group), rises in myoglobin, creatine kinase and LDH were smaller on collagen, while C-reactive protein showed no clear effect. Tendon size, tendon and muscle ultrasound and collagen-related blood markers, all registered primary outcomes, are not reported in either paper. Because a blend was tested, the result cannot be credited to PeptENDURE alone.