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Hello, and welcome back to Everyday Science.

If you are on social media, you have probably noticed an increasing number of adverts for products called peptides, claiming to boost health in various ways.

You may have previously heard of peptides as ingredients in skin creams, or might remember from school that peptides are small protein-like molecules found naturally in the body.

But the adverts are for a new breed of injectable peptides, which are being promoted by influencers for uses including weight loss, muscle growth, tissue regeneration and as broad “anti-ageing” tools.

They are basically experimental drugs that have not undergone the usual clinical trials or passed regulatory approval, and so carry great health risks, experts have warned.

Indeed, serious side effects have already been reported and a UK man in his thirties has died after taking a peptide – although it has not been confirmed if the drug was responsible.

The reason peptides have so many different claimed uses is that they are a broad category of biochemicals. In their natural form, in the body, they are signalling molecules that pass instructions between different cells, often acting as hormones.

Peptides have been turned into pharmaceutical drugs before. Insulin, used by diabetics, is a peptide, as are the slimming jabs Wegovy and Mounjaro.

To be clear, there are no serious health concerns about Wegovy or Mounjaro when bought from regulated online pharmacies, because these drugs have passed extensive safety testing and been approved by bodies such as the UK’s Medicines and Healthcare products Regulatory Agency (MHRA).

But the approved slimming jabs may have helped kickstart the peptides craze, by getting more people used to injecting themselves with pharmaceuticals.

The other spur may have been that when Wegovy first launched in the US in 2021, it was too expensive for most people to afford, costing up to $1,350 a month. Into the breach stepped shady manufacturers based in China, which sold the same compounds as in Wegovy and Mounjaro, without even the need for a doctor’s prescription.

Despite the clear risks of buying injections from overseas businesses with no regulatory oversight, this may have fostered wider acceptance of online drug purchasing among consumers in the US and UK, said Robert Bradford, superintendent pharmacist at Oxford Online Pharmacy. “The idea of injecting a drug that you bought online would have been anathema to anybody 10 years ago,” Bradford said.

The prices of Wegovy and Mounjaro have since reduced somewhat, but now interest is growing in other kinds of peptides, also fostered by the growth of wellness and biohacking influencers – who often get kickbacks from sellers.

One of the most popular peptides is a third type of slimming jab, called retatrutide – also sold as reta or reta peptide. This is actually a legitimate pharmaceutical that manufacturer Eli Lilly is investigating in clinical trials – but the drug has not yet been approved by bodies such as the MHRA and so it is still classed as experimental.

In 2023, however, word spread that retatrutide had caused even more weight loss than Wegovy and Mounjaro in a small early-stage clinical trial – 24 per cent, compared with about 15 and 20 per cent respectively for the other two jabs.

Retatrutide seems particularly popular with male gym-goers as its promoters claim it helps build muscle as well as reduce fat. “While the early research is promising, more evidence and regulatory review is needed before retatrutide can be considered a safe and approved treatment option,” said Jason Murphy, head of Pharmacy at Chemist4U.

Recently, things have got worse – there has been an explosion of online sales of other kinds of peptide drugs that are being investigated for different medical uses, although most of them have been tested only in very limited human studies.

Claims for these peptides include tissue regeneration, sleep regulation, tanning and broad anti-ageing effects.

As these drugs have not yet been shown to be safe and effective by large clinical trials, these experimental peptides bring additional risks, in that they could cause dangerous side effects even if the drug in the vials is 100 per cent pure and at the stated dose. “Anything could happen, from serious illness to death,” said Bradford. “We’re in the Wild West.”

It is impossible to know the extent of the online sales, but just searching for “peptides” on sites like TikTok and Facebook brings up huge numbers of posts from sellers and influencers, showing the demand.

Last month, a London endocrinologist told The Guardian he encountered patients “day in day out” who were using experimental peptides. And earlier this year, the MHRA raided two premises in Lincolnshire and Nottinghamshire that were dealing in unlicensed retatrutide and other peptides.

While retatrutide has not yet been approved, the drug does at least have some early data suggesting it is likely to be effective and safe. But the rest of the experimental peptides are more unknown quantities.

One of the most popular, called BPC-157, is promoted for tissue regeneration, with influencers claiming it can help after muscle strains, for instance. But animal studies suggest it works by promoting blood vessel growth, which could in theory also promote growth of cancers.

Another experimental peptide, called melanotan, causes skin tanning – it is sometimes called the “Barbie drug”. But there have been reports of it causing skin cancer as well as rapid changes to moles and pigmented areas of skin, according to the US Skin Cancer Foundation.

“The risks are very serious, from allergic reactions to even fatalities,” said Bradford. “The products might not be made with a sterile manufacturing process. It could be contaminated with bacteria, fibres, bits of plastic. And then what drug is in there, what is the dose?”

Already, one British man in his thirties has died after taking unlicensed retatrutide and there have been 76 other adverse reactions from the same drug reported to the UK Medicines and Healthcare products Regulatory Agency (MHRA), the British Medical Journal reported last month.

It is hard to know how authorities can eradicate the trade. Online sellers usually market their products as for research purposes only or not for human consumption, which technically means they are not acting illegally.

Even with the ones that clearly market their products as for human use, UK bodies can do little about companies based in China.

Health minister Dr Zubir Ahmed said: “These medicines are made with no regard for safety and pose serious risks. [The MHRA] raids have taken dangerous, unregulated products off our streets.”

The US FDA, on the other hand, under Trump’s controversial health secretary Robert F. Kennedy, has taken a more pro-peptide stance. Kennedy even said on the popular Joe Rogan podcast that he is a “big fan” of peptides and used them himself.

The FDA ruled last month that six experimental peptides can be sold by certain US pharmacies on the basis that people are already buying them on the black market and it would be safer if they could buy them from legitimate sources. Other health experts said this was misguided.

For UK consumers, Bradford said: “Unless you’re using a regulated and registered pharmacy, do not inject any drugs that you buy online because you just cannot be sure of what’s in them, whether they’ll even work, and whether you risk serious harm to yourself.”

I’ve been watching

At the Edinburgh Fringe Festival, I ended up seeing – somewhat against my wishes – a spoof musical based on the ice hockey gay-romance TV series, Heated Rivalry, and was glad I was overruled.

I had given up on the TV series itself after the first episode, but the musical, called Heated Rivalry: The Unauthorized Musical Parody, works because it is both homage to the show, and merciless ridicule of it. The songs are catchy, the dialogue snappy and the laughs are frequent. The show is on in Edinburgh until 30 August and comes to London in October.