Collagen supplements changed some short-term blood markers related to bone remodeling and inflammation in a small trial of female distance runners, but the findings do not show that the supplements improved bone strength or reduced the risk of stress fractures.
The randomized, double-blind pilot study included 22 women ages 18 to 35 who ran at least 35 miles per week. Half took 20 grams of collagen peptides daily for four weeks, while the other half received a calorie-matched placebo. Researchers measured blood markers associated with bone formation, bone breakdown and inflammation before and after the intervention.
The study, published in Frontiers in Nutrition, found a small increase in a blood marker tied to bone formation among runners who took collagen. However, the difference between the collagen and placebo groups was not statistically significant.
Researchers also found changes in two other markers involved in inflammation and bone remodeling, while a marker of bone breakdown did not change. Taken together, the results suggest collagen may affect some short-term biological processes, but they do not show that it strengthens bones or prevents injuries.
The researchers did not test whether collagen increased bone mineral density, improved bone structure or lowered the risk of stress fractures. The four-week study was also too short to detect meaningful changes in bone mass.
Blood biomarkers can help researchers explore how a supplement may affect the body before structural changes become measurable. They are not substitutes for clinical outcomes, however. A change in a marker associated with bone formation does not necessarily mean someone developed stronger bones or became less likely to experience an injury.
Bone health is an important concern for distance runners because repeated training places substantial stress on the skeleton. Running itself can support bone adaptation, but problems may develop when athletes do not consume enough energy to support training, recovery and normal body functions.
“Oftentimes, we associate running with being bad for us, bad for our bones, because runners are at a higher risk of stress-related injuries,” study leader Jennifer Fields said. “But oftentimes, it’s due to just simply under fueling and not giving your body enough calories to support training and recovery and adaptation.”
Low energy availability can disrupt hormones involved in bone remodeling, particularly in women. Over time, inadequate fueling may contribute to reduced bone formation, menstrual changes and a greater risk of bone stress injuries.
Collagen is a major part of bone and connective tissue, which is why researchers are interested in whether collagen peptides might influence bone remodeling. Some small collagen fragments can be absorbed during digestion and may act as signals to bone cells, but scientists still do not know whether those effects translate into meaningful improvements in bone health.
The new trial does not show that collagen should replace adequate calories, carbohydrates, protein, calcium or vitamin D. For runners who are underfueling, adding a collagen supplement would not correct the broader energy shortage affecting bone recovery and hormone function.
The participants also were not selected because they had osteoporosis, low bone density or menstrual disturbances. Women with amenorrhea or oligomenorrhea were excluded, and participants generally had normal bone density at the start of the study.
That limits how confidently the results can be applied to runners at greatest risk of impaired bone remodeling.
The trial’s small size also raises the possibility that some findings occurred by chance or that meaningful differences were missed. With only 11 participants in each group, the study was not designed to provide a definitive answer about collagen and bone health.
“We’re seeing some good preliminary data to show that four weeks is sufficient to move some of those acute biomarkers,” Fields said.
Larger studies would need to follow runners for longer periods and measure outcomes such as bone density, bone structure and stress injury rates. Researchers would also need to determine whether any benefit depends on a person’s overall energy intake, protein intake, menstrual health or baseline bone status.
The research was funded by the National Strength and Conditioning Association Foundation.