SOME PEOPLE ARE pumped about peptides. Reddit is stocked with self-experimenters who say they've injected themselves with synthetic peptides and have seen results: more muscle, a sharper mind, greater amounts of energy.
With the explosion of peptide popularity, I reviewed over 100 studies on the 19 peptides that the FDA has considered removing from the Category 2 Bulk Substances List. The goal was to help current users—or those curious on the peptide hype—to better understand the effectiveness and safety of each substance. (You can find a full breakdown in our ultimate peptide guide).
I used to work in a neuroscience lab where I was trained to read research studies with a healthy dose of skepticism. The most important skill was not looking at what the researchers found but how they came to that conclusion—to read not just the study, but how it was constructed. Was it a shoddy experimental design? How did they analyze the data? What other variables could have been responsible for the final results?
When I looked at synthetic peptide research through this same lens, I was amazed by what I found.
Most Peptide Studies Are Still in Animals
I KNOW FIRSTHAND how vital animal studies are. My graduate research was on the neurochemistry of addiction—and we had to use rats. That’s because it’s unethical to give people drugs (and then dissect their brains after). Animal studies are important for testing whether a drug works and, most importantly, assessing short-term and long-term side effects. Rodents and primates have a high genetic similarity to humans and share similar physiology, especially in the brains and heart.
But at the end of the day, a rat is not a human. While a peptide may work well in a rat, there is no guarantee it will confer the same health benefits to humans. The synthetic peptide Selank, for example, only has rodent studies to back up its alleged nootropic effects. Another peptide, TB-500, also has a good amount of animal research looking at its accelerated healing effects. Yet there’s not much about how the synthetic TB-500 fares in humans (plus multiple studies link it to cancer—yikes).
Conflicts of Interest Abound
BIAS IN RESEARCH is a big deal. That's why it's important to look at the disclosures and conflicts of interest sections of studies to determine who might benefit from the research findings.
In my analysis of peptide research, there were multiple instances where the only studies with positive results were funded by the makers of said peptide (AOD-9604 is one example) or where positive results mainly came from a single scientist (Semax).
Several peptide vendors also tend to cite research on the natural biological peptide and apply the benefits to the synthetic version. That’s because artificial versions mimic fragments of the natural peptide used to send messages throughout the body. The problem is that doesn’t guarantee a 1:1 replica of the real thing. Because there’s no regulation on most peptides, the purity and structural stability may vary.
Many Peptide Studies Are Decades Old—and Poorly Constructed
MANY STUDIES AVAILABLE range from the 1980s to the early 2000s. That may sound (sorta) recent, but that's pretty much an eternity in research time, because data can quickly become outdated as research progresses. I understand the lack of traction in peptide research: The FDA has an iron grip on how much leeway researchers have in accessing these peptides, let alone giving to people for the sake of science.
Still, many studies that are available were poorly designed. There were multiple studies that lacked a control group (important in understanding whether a drug actually worked or if it was a placebo effect) and sample sizes of less than 20 people (running the risk that this might be a chance finding that wouldn’t apply to the general population). That was the case for human studies on BPC-157 and DSIP.
Some Peptides Deserve More Research
THERE WERE A small handful of peptides that actually had the scientific evidence to back up their claims—or have potential if there were looser restrictions for testing them on people.
One standout was Thymosin Alpha-1. The injectable peptide helps with increasing and restoring immune function. There is clinical evidence that Thymosin Alpha-1 does enhance vaccine response and boost the production of certain immune cells. The peptide has been a popular option for people who have long COVID and other immune disorders.
It’s likely that there may have been more opportunity to study the peptide because it’s more widely accessible than others. (Thymosin Alpha-1 is approved in over 30 countries for treating hepatitis and other infections). It’s also a reminder that some people are turning to these substances out of genuine necessity, and using the research currently available to try to improve their health when traditional medicine has failed them.
Peptides aren’t going away. As they continue to surge in popularity, so too does the demand for good data.
Jocelyn Solis-Moreira, MS is the associate health & fitness for Men's Health and has previously written for CNN, Scientific American, Popular Science, and National Geographic before joining the brand. When she's not working, she's doing circus arts or working towards the perfect pull-up.
