UCLA Health team’s review of six popular peptides finds little evidence and potentially concerning safety issues.
August 31, 2026
By Mary-Rose Abraham, Senior Science Writer
5 min read
Peptides are short chunks of protein with specialized functions in the body. Insulin and GLP-1, both of which have U.S. Food and Drug Administration approval, are two of the most well-known.
Yet claims promoting hundreds of unapproved peptides have flooded social media. These supplements, mostly self-injectables, promise to build muscle, speed up the healing of injuries and even slow aging.
“It’s a lot of marketing and very little substance,” said Thomas Kremen, MD, a sports medicine specialist and associate professor in the department of orthopedic surgery at the David Geffen School of Medicine at UCLA.
“The evidence that these peptides are effective is just not there.”
Dr. Kremen currently serves as a team physician for the Los Angeles Chargers, the Los Angeles Lakers, USA Basketball and the UCLA Bruins NCAA Division I intercollegiate athletics team. He was also the chair of USA Swimming’s Sports Medicine and Science Committee from 2016 to 2024 and the team physician for the USA Swimming Team at the Tokyo 2021 Olympic Games.
He and third-year medical student Kushagra Tewari are among the authors of an extensive reviewof the current scientific literature on six emerging peptides: BPC-157, TB-500, CJC-1295, MK-677, ipamorelin and GHK-Cu. The team analyzed 565 studies that looked at the peptides’ effects on musculoskeletal treatment, tissue recovery or performance in animal or human models.
What were the limitations you saw in the studies you looked through?
Dr. Thomas Kremen: More than two-thirds of these studies were only done in animals. We found they had some promising but variable effects on tendon, muscle, bone and ligament healing – but those effects may look very different among rodents compared to humans. Also, the studies don’t assess what the negative aspects could be, so they’re not telling the whole story.
A handful of human studies revealed modest improvements at best for non-orthopedic indications. However, there were essentially no studies demonstrating significant clinical benefits for musculoskeletal conditions. Those clinical studies that did appear to show some positive clinical findings were done very poorly. Most lacked robust controls or rigorous study designs. For example, they would take a topical agent with limited clinical evidence for the treatment of a skin condition, and try to claim its beneficial effects as an injectable therapy for musculoskeletal problems.
Kush Tewari: Another issue was conflicting interests. We saw that with one of the biggest studies that was done with BPC-157. The group that did that study had a financial interest in the compound itself.
The quality of these studies needs to be much stronger. That’s one of the biggest things that we came across.
What were the risks you found associated with these peptides?
Dr. Kremen: In one of the documented trials for the peptide MK-677, they stopped the trial because of a higher rate of congestive heart failure in one of the groups. In my own practice, I had a patient who was getting a rotator cuff repair. That’s usually an outpatient procedure. He was seemingly young and healthy. But he had a cardiac output that was so low, it was unsafe to do the surgery unless we did it in the hospital.
He admitted to taking peptides. I can’t really say causality, but it’s certainly a concern.
What are the issues with how these peptides are made or marketed?
Dr. Kremen: These supplements are not regulated or vetted by the FDA. You don’t really know what else is on that conveyor belt during production or if that bottle contains what the label says. Some tests show they contain dangerous substances, like arsenic or lead.
Many of the products that are discussed in our article are not made in the U.S. When it comes over from China, the label on the bottle may say, “not for use in humans.” It then can be mixed, by a compounding pharmacy, with something that may or may not be approved in the U.S. and then you have no idea what’s in that vial.
Tewari: The compounding pharmacies on social media sell them as “gray market peptides.” They’re marketed for “research purposes only,” in an attempt to get out of any type of liability.
I’ve also seen that when people aren’t getting the desired effect from these compounds, they buy more from different websites. That increases the danger of using tainted products.
What conversations are you having with patients and peers about peptide supplements?
Dr. Kremen: The huge push from social media and the non-medical, non-peer-reviewed resources have the public’s attention. I have patients come in all the time saying, ‘Hey, my friend was taking this,’ or ‘I heard about this on social media, what do you think?’ Sometimes they’re already trying it before they come to see me. Patients are trying to recover from surgery faster, are trying to enhance their longevity or perhaps do more rigorous activities for a longer duration than their parents did. Usually, I have a very candid discussion with them about the risk profile of these supplements.
Tewari: I played baseball in college. People would talk about supplements in the sports world, but these substances were banned and athletes were continuously tested so they weren’t used.
Now I see it more in the general population, such as athletes who have stopped playing and recreational gym-goers. They’re trying to bench-press or squat the maximum weight and may turn to untested performance-enhancing peptides to get that competitive edge. If they get injured, that’s when they start looking at these other peptides marketed as injury recovery products.
Dr. Kremen: The bottom line is there is little to no evidence these peptide supplements work. And you don’t know what’s in them, so why take the risk?
This is very much a situation where the marketing is well ahead of the science. My advice would be to wait until scientists study their effects in a rigorous fashion.
So what can people do to optimize their recovery?
Dr. Kremen: Everyone’s looking for something to improve their health, their longevity, their performance. As clinicians, we want to empower patients to meet their goals.
There are no mysteries in how to appropriately optimize overall performance: sleep, nutrition, strength and aerobic training. These are the building blocks of any successful athlete. As for recovery, trust the advice of expert medical professionals. They can precisely diagnose and develop treatment plans for a patient’s specific needs.
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