The internet loves peptide therapy. Is it really a miracle cure?

It seems as if everywhere you turn, celebrities and influencers are talking up peptides. Peptides can give you younger, brighter skin; help you build bigger muscles; let you live longer and heal faster.

Wonderful. Just one question: What exactly is a peptide?

Chemically speaking, peptides are simply short chains of amino acids that play useful roles in our cells, like regulating hormones or reducing inflammation. Our bodies naturally create thousands of peptides; thousands more are made synthetically in labs.

Creatine is a peptide; so are medications like Ozempic. Hormones like insulin and oxytocin are peptides, too.

But when online influencers talk about peptide therapy, they are generally referring to a vast constellation of emerging or experimental products, often in skin care, fitness or biohacking. These can be swallowed, injected or rubbed on the skin.

While some of these treatments are reasonably safe and have been studied by the Food and Drug Administration, others can be dangerous. For example, the “Barbie” peptide is often promoted by influencers and online clinics as a healthier way to tan without the sun — even though the FDA has warned of “serious safety risks,” and research suggests it’s linked to an increased chance of cancer.

While it’s impossible to list all the potential benefits and risks of every peptide, there are a few things to know about the most common uses.

Over the past two years, interest in skin care peptides has skyrocketed. Cosmetics giant Sephora now offers hundreds of topical peptide products that promise to pump collagen into skin, plump lips and depuff eyes.

But are the products effective? There certainly can be “some benefit” to peptide therapy for skin care, said Dr. Adam Friedman, professor and chair of dermatology at George Washington University. “They’re not a scam.” But they also shouldn’t be your only skin care solution, he added.

There are dozens of natural peptides in our bodies that promote collagen production and regenerate skin cells — which keep our skin looking healthy. Peptides like palmitoyl pentapeptide (trademarked as Matrixyl in many popular creams) signal to the skin to create more collagen and elastin. Others, like GHK-Cu, deliver copper to the skin, which helps it regenerate. There is even a peptide that acts like Botox — helping relax facial muscles to soften wrinkles.

Though limited, some research suggests that topical serums and oils with these chemicals can help improve the skin’s appearance. Historically, the difficulty has been getting these peptides to penetrate the skin and stay stable.

“If you think about a peptide, how freaking fragile must that be,” Friedman said, describing its delicate chemical structure. The outer layer of our skin acts as an incredibly effective barrier, blocking germs, toxins and peptides alike.

But new topical creams can carry peptides into the body, using advanced chemical tools such as nanoemulsions and liposomes. (Another popular option in Hollywood is injectable peptides, but Friedman said there’s still not enough evidence they are “safe and effective” for humans.)

There is no reliable way to know whether products use these, Friedman said, or how well they work. If you are determined to try a peptide cream, then, “go with well-established brands,” he added, since they are more likely to put resources into development and testing.

While more research is needed, dermatologists generally agree there are few risks in trying topical products, but say to stop immediately if you experience a reaction.

Even with the most effective products, experts say to keep your expectations low. “Think of peptides as sidekicks rather than hero ingredients,” Friedman said. The best anti-aging skin care tools are still sunscreen, moisturizers and retinoids (for those who tolerate them), he added.

Another popular group of peptides prompt the brain to increase the level of human growth hormone (HGH).

Federal law prohibits synthetic HGH from being prescribed for reasons other than those approved by the FDA, mainly to treat people with deficient levels, though it’s widely taken illegally as a performance enhancer.

Given the legal limits placed on HGH, some clinics have turned instead to prescribing peptides like tesamorelin and, most commonly, sermorelin, as an injection or pill help stimulate the body to create more HGH.

These peptides are both legal to prescribe off-label because they were part of previous FDA-approved medications. Unlike HGH, moreover, no federal law limits their broader use. This makes them “one of the only ways to legally increase growth hormone” in otherwise healthy adults, said Tenille Davis, a spokesperson for Alliance for Pharmacy Compounding.

Regardless of the method used to increase HGH, it’s not clear how much higher levels actually improve strength and build muscle in healthy adults. Some small trials have found modest increases in lean body mass among older men who took these types of growth hormone-releasing peptides, but this didn’t translate to improved strength or recovery.

High levels of the hormone may come with serious risks. Research has linked persistently high levels of the hormone to diabetes, certain cancers and acromegaly, a condition that causes the bones of the hands, feet and face to enlarge over time.

Though sermorelin is often promoted as a safer and more natural way to increase HGH, it carries the same risks over time, said Dr. Shlomo Melmed, an endocrinologist and expert in pituitary disorders at Cedars-Sinai Medical Center in Los Angeles. Sermorelin is in essence “a surrogate for growth hormone treatment,” he added. Sermorelin, tesamorelin and synthetic HGH are all banned by most major sports organizations.

Clinics that prescribe the medication, for their part, say they use strict screening and monitoring to manage side effects — and “cycle” the therapy to mitigate the risks of long-term use.

In a recent episode of his podcast, Joe Rogan told his millions of followers that a peptide nicknamed the “Wolverine” shot cured his chronic elbow tendinitis after just two weeks. Fitness influencer Ryan Humiston, who tests “every peptide I can get my hands on,” told his millions of followers that the peptide pinealon improved his sleep apnea.

Devoted biohackers — a growing community of self-experimenters looking for ways to optimize their health and longevity — point to extremely preliminary studies that suggest injecting peptides like epitalon may extend life, melanotan II could boost libido, and semax or selank could improve cognition.

But much of this research is still conducted on cell cultures and hasn’t even progressed to animal trials. None of these peptides have met the FDA’s criteria to be approved for human (or even veterinarian) use.

And since the chemicals are considered “research-grade” and intended only for laboratory work, regulators don’t require the same quality measures used for approved drugs. There is no way to assess their stability, potency or even ingredients, Friedman said.

Still, these experimental drugs are surprisingly easy to come by — even with known risks.

The Wolverine shot’s peptide, called BPC-157, can cause pain and swelling, but other experimental peptides are tied to more serious issues. TB-500, a synthetic version of another peptide marketed as a wound-healing and recovery tool, has not undergone human trials, and high levels of the peptide have been linked to tumor growth.

Health Secretary Robert F. Kennedy Jr. has expressed support for deregulating some of these research-grade peptides, making it easier to study them in human subjects.

However, the growing popularity of these drugs shows that many people will experiment with them long before science confirms they work or are safe.

Melmed cautioned anyone thinking of doing so to be “wary of any promises” that a particular peptide will help a person “live longer or have a healthier life span.”

For the “peptide curious,” Friedman suggests keeping in mind your ultimate goal — whether it be firmer skin, stronger muscles or a longer life. “Then you can ask: Are there proven, regulated therapeutic approaches for that? Often the answer is yes, and it may or may not involve peptides at all.”