A science feature published by ZME Science argues that some of the fitness industry's peptide claims have a scientific basis while others run considerably ahead of the evidence. The piece separates food-derived collagen and whey peptides, which have actually been trialed in sports nutrition, from the experimental injectable compounds sold for laboratory research only.

Peptides are short chains of amino acids, the fragments left when a protein is cut into smaller pieces. Collagen peptides are made by extracting collagen from animal tissue such as cow hides or fish skin and using enzymes to break the large molecules into shorter chains, a process called hydrolysis.

Whey still wins on size

In a 2022 randomized trial in the International Journal of Sport Nutrition and Exercise Metabolism, 22 previously untrained adults did the same ten-week resistance program while taking either 35 grams of whey or 35 grams of collagen peptides with added leucine. Thigh muscle thickness rose by an average of 8.4 percent in the whey group against 5.6 percent in the collagen group, with upper arms at roughly 10 percent versus 6 percent.

Strength and power gains were similar between the two groups, which the article attributes partly to the nervous system getting better at activating muscle early in training. The trial was small, but the direction is unsurprising: collagen lacks tryptophan and carries relatively little leucine.

Where tendons come in

The more interesting case is connective tissue. A 2026 systematic review of eight randomized trials involving 257 participants found that three of four studies measuring tendon size reported greater increases among people taking collagen, with higher-dose studies also reporting improved tendon stiffness.

Those effects showed up most clearly alongside substantial resistance training, and the same review found no extra gain in overall muscle strength beyond training itself. A 2024 meta-analysis in Sports Medicine pooling 19 studies and 768 people identified modest benefits across lean mass, tendon structure and recovery, but rated much of the evidence low or very low certainty.

What is still unsettled

Scientists have not established whether collagen supplements prevent sports injuries, and the article is blunt that swallowing collagen does not route it to an aching knee. A 2024 analysis of 35 trials in 3,165 osteoarthritis patients found small to moderate improvements in pain and function, though reduced pain is not evidence that cartilage regenerated.

The closing position is the unglamorous one. Peptides are not a single category of miracle supplement, and the most dependable formula remains regular exercise, adequate nutrition, sleep and recovery time.