From influencers to athletes, high-profile figures are hailing peptides as the route to wellness, claiming they help with injury repair, weight loss, anti-ageing and mood. We take a look at what these substances are, and the murky industry surrounding them.
What are peptides?
Peptides are short chains of amino acids.
Some peptides occur naturally in the body and have particular functions. For example, the hormones insulin, oxytocin and vasopressin are peptides involved in regulating blood sugar levels, social behaviours, and water retention and blood pressure, respectively.
Other naturally occurring peptides are formed when proteins are broken down in the body, for example, when food is digested.
However, in recent years there has been a boom in interest in using peptides for therapeutic purposes, from weight loss to anti-ageing and recovery from injury.
These include approved prescription weight-loss medications based on synthetic peptides that mimic natural hormones, such as semaglutide (found in Wegovy) and tirzepatide (found in Mounjaro).
However, many peptides on the market have not undergone the strict regulatory processes like those used in medications. Instead they are unregulated, experimental peptides being sold for self-injection.
Who is injecting peptide products?
According to Dr Luke Turnock, a senior lecturer in criminology at the University of Lincoln, peptides were initially a niche interest, largely found in the 2010s among powerlifters and bodybuilders.
“And at that time, it was mostly the growth-hormone-releasing peptides, GHRP-2, GHRP-6, but there was some chatter about these emerging peptides like TB-500,” he said, noting that these are not only taken for alleged effects on muscle growth and tissue repair, but to avoid the slump many experience when they stop taking steroids.
Since then, however, interest has exploded.
Among others, the US podcaster Joe Rogan has alleged the peptides BPC-157 and TB-500 – a combination known as the “Wolverine stack” after the Marvel superhero – help with injury recovery. Other popular peptides include CJC-1295, MK-677 and ipamorelin that are touted as helping build muscle, and GHK-Cu, which is purported to have anti-ageing effects.
As a result, social media is awash with people talking about peptides, including how to sell them, where to buy them and how to inject them.
“I still think it’s mostly people interested in health, fitness and wellbeing,” said Turnock, who has researched the use of such peptides in the UK.
Is there evidence to support the claims for these experimental peptides?
Academics have noted that most experimental peptides have little scientific evidence to support the claims being made, and where studies do exist these are often in animals or cells.
For example, according to a recent review by researchers in the US looking at peptides often marketed to patients with musculoskeletal injuries, BPC-157 “demonstrated potential benefits in tendon and muscle repair, but these findings are largely unvalidated in human trials”, with no randomised control trials in humans relating to such uses, and the only case series having serious flaws.
They added that a peptide called TB-4, and a similar synthetic peptide, TB-500, showed some signs of promoting blood vessel formation and tissue repair in cell studies and animal research, but the experts noted that human data around musculoskeletal conditions are lacking. They said there had been no studies of TB-500 in human participants. What’s more, both are banned banned substances in sport, appearing on the World Anti-Doping Authority’s prohibited list.
And there is another issue around such peptides: “Importantly, information regarding the indications, dosing, frequency and duration of treatment remains unknown,” the researchers wrote.
What is the legal situation?
Many popular peptides are not considered medicines in the UK, meaning they are unregulated by the UK’s Medicines and Healthcare products Regulatory Agency (MHRA).
However, the situation changes if sellers – be they websites, clinics or social media vendors – claim the peptides have medicinal effects.
Lynda Scammell, the head of borderline products at the MHRA, said: “Where medicinal claims are made, or products are being used in a way which brings them within the definition of a ‘medicinal product’ under the Human Medicines Regulations 2012, a peptide-containing product must hold a marketing authorisation to be legally sold or supplied in the UK.
“If a product is classified as a medicine and is not appropriately authorised, we are able to take action to ensure regulatory compliance, including the removal of the product from the UK market where necessary. The specific action taken is determined by consideration of all the available evidence and relevant legal precedents.”
The MHRA also stressed that labelling peptides “for research purposes only” – a ruse used by many social media vendors and websites – was not enough to avoid scrutiny.
“We disregard claims that products are for ‘research purposes’ if it is clear that such claims are being used as an attempt to avoid medicines regulations,” said Scammell. “If there is evidence within the promotional material that the products are in fact unauthorised medicines intended for human use, we will take appropriate regulatory action.”
What is the problem?
Experts have raised a number of concerns about the the risks of using experimental, unregulated peptides.
Prof Adam Taylor, from Lancaster University, said potential benefits in pre-clinical studies – such as those in animals and cells – do not necessarily mean a peptide is beneficial for humans.
“We know for every drug that’s been approved going through the safety profile, the toxicology, the pharmokinetics that has then been approved … in humans, there’s just as many, if not more, that have fallen by the wayside along the way because they don’t have a specific benefit for whatever it was we were looking to treat,” he said.
As well as concerns about the purity of the products, Taylor noted that peptides produced for research purposes could contain other ingredients that were dangerous for humans, or bacterial endotoxins. The latter can trigger septic shock.
He said naturally occurring peptides were kept within very particular levels by the body, meaning that increasing their levels via injections could throw its systems out of balance. What’s more, many peptides are involved in lots of different pathways in the body, so taking them could have unexpected results.
Another concern is that certain peptides are produced in greater quantities in some tumours, meaning injecting similar substances could be problematic.
“There’s absolutely no evidence of this happening at the moment. But when we think about risk and benefit, the risk is if you’ve got low-grade inflammation, you’ve got early signs of cancer happening, are you going to overload that pathway and promote that cancer to grow bigger, faster?” Taylor said.
As well as the risks of self-injection, such as accidentally injecting air, there were concerns that peptides could interfere with medicines people -were already taking.
And, while it is unclear how long people are taking peptides for, there is little, if any, active monitoring of their effects.
“If something’s going to go wrong in the short-term [users will] not see it. And if something begins to progress slowly, again, they’re not going to see it and potentially the damage is all already going to be done,” Taylor said.
