Controversial wellness products called peptides are rising in popularity as they're touted by leaders like Health and Human Services Secretary Robert F. Kennedy Jr.

While some peptides — including drugs like Ozempic — have been rigorously tested and approved by the Food and Drug Administration (FDA), many peptides are untested and unregulated. These untested peptides are often accessible online for anyone to purchase from loosely regulated manufacturers. There's now a multibillion-dollar gray market for these products, in which many peptides are sold without human-safe manufacturing processes or human testing to demonstrate their effectiveness, scientists say.

Recently, an FDA advisory panel voted to increase consumers' access to several peptides, saying the products — marketed for sleep issues, wound healing, cognitive disorders and more — should be available through compounding pharmacies with a prescription. These pharmacies, which offer customized medications, are subject to less oversight than traditional pharmacies and can distribute drugs that have not been FDA approved. Opponents of the advisory panel's decision argue that these peptides have not gone through rigorous clinical testing and could pose risks to consumers.

So what does this advisory panel decision mean for peptide regulation, and how might it affect consumers? And at the end of the day, are the peptides safe? Here's what you need to know.

What are peptides?

Broadly speaking, peptides are short chains of amino acids, the same building blocks that make up proteins. Peptides are smaller than proteins, and their structures are less complex.

Body-made peptides can act as messengers throughout the body, telling cells what to do. Some are considered hormones and some are not. There are about 7,000 known peptides that help organs communicate with each other and direct various bodily functions and behaviors, including blood sugar control and mood. Insulin, oxytocin, vasopressin and endorphins are examples.

The first synthetically manufactured peptide was insulin, which is normally produced by the pancreas to regulate blood sugar levels but is lacking in people with diabetes. Recently, peptides called GLP-1 agonists — the class of drugs that includes Ozempic and Wegovy — have become incredibly popular. Naturally expressed in the gut, the GLP-1 hormone functions, in part, by telling the brain that you've had enough to eat.

While these peptides are usually injectable medicines, others are taken orally or inhaled via nasal sprays. Peptides that are intended to treat or prevent disease, or to affect the structure or function of the body, are legally considered drugs and should be regulated and approved for safety and effectiveness by the FDA. (However, that doesn't always happen, as we'll explain in the following section.)

Plant- or food-derived peptides, such as collagen peptides, are considered supplements. Supplements are less strictly regulated than drugs are, which results in their potency and purity being more variable than that of approved drugs.

What uses of peptides are backed by scientific evidence (and which aren't)?

Peptides like insulin and GLP-1 agonists have been extensively studied for years through rigorous trials to determine whether they are safe and effective for human use and to treat specific ailments. This is what is required to obtain FDA approval. The FDA has approved the use of about 100 peptides for therapeutic use against specific conditions, such as diabetes and multiple sclerosis.

That said, there are also peptides that have become popular for general wellness and even "biohacking," a form of self-experimentation to optimize physical and mental performance. These unapproved peptides are sold online, often with the label "research use only." The label acts as a loophole to legally bypass the regulatory oversight that would usually be applied to approved drugs. That said, the FDA has come after companies that explicitly advertised and sold these products for human use, despite that research-only label.

"Only a few peptides are actually FDA approved meaning they are safe and efficacious for certain diseases," Dr. Jonathan Long, a peptide researcher and associate professor of pathology at Stanford University, told Live Science in an email. "Many other peptides are still not FDA approved and should be considered experimental."

How is the regulation around peptides changing in the U.S.?

In July, an FDA advisory panel discussed seven unapproved peptides and voted to recommend increased access to six of them. The products are marketed for myriad uses, including boosting muscle recovery, treating gut damage, dampening inflammation, improving metabolism, enhancing cognition and extending longevity.

The panel recommended that these peptides be allowed to be prepared and distributed by compounding pharmacies. This is a recommendation and not a binding decision, meaning the FDA can now decide whether to go with the panel's idea. The FDA must complete a formal rulemaking process before any policy change becomes final.

According to Dr. Katrin Svensson, another peptide researcher and associate professor of pathology at Stanford University, this move could represent a reversal of U.S. peptide regulation. The FDA restricted these six peptides and others from compounding in 2023, deeming them too dangerous for compounding pharmacies to make, she told Live Science in an email.

"[These peptides] are not approved medicines, they have not been tested in humans and have little or no experimental data in cells or animals," she emphasized.

Notably, the FDA advisory committee includes eight members recently appointed by Kennedy, many of whom have ties to the peptide industry. Although their recommendation is not binding, this support of increased access to unapproved compounds could spur online sellers to promote even more unregulated peptide usage. There's also a concern that allowing the products to be sold more widely could undermine research into their legitimate medical uses, given companies can sell them without hard evidence.

What is the scientific evidence behind the decision?

"There is no new scientific evidence tied to these decisions, which is partly the problem," Svensson said.

Long agreed. "This decision does not say that these peptides are more scientifically legitimate, or that they are safe, or that they are efficacious," he said. "The only thing this vote does is to potentially allow more people to access these peptides via compounding pharmacies."

Are the changes to peptide access expected to help or hurt consumers?

While increased access to peptides may result in more people injecting themselves with untested substances, compounded peptides are at least safer than research-grade peptides, experts told Live Science.

"Obtaining peptides from a compounding pharmacy means that it will be the peptide in the vial, and that the purity will be high, and that the vial will be sterile," Long said. "But it still does not mean that these peptides are safe for human use, or that they can treat any human diseases."

However, Svensson cautioned that peptides are not one thing.

"They range from medicines to unproven experimental compounds, and this shift is driven by policy, not new science," she said. "Easier access doesn't lower the evidence bar, and the trials that would show whether these actually help still haven't been done."

What should consumers know about peptides?

It's possible that allowing compounding pharmacies to make the six peptides could mean they're less likely to contain contaminants and may be more consistently pure than completely unregulated versions of the products. But that doesn't mean they will do what they have been promoted to do or be safe to use in the long term or in combination with medicines or with other peptides.

"'Allowed to be compounded' does not mean 'FDA-approved,'" Svensson said. "For most wellness peptides the human evidence is thin, the right dose is unknown, and you can't be sure what's in the vial."

"I myself personally would not be injecting myself with any experimental molecules," Long said.