Today in Science: The real science of peptides

They're trending, but have virtually no clinical data to support them ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­

April 21, 2026—We get into the real science behind peptides (there's not much). Plus, NASA's moon landing plans may be delayed, and birth order affects risk for many health conditions.    —Andrea Gawrylewski Chief Newsletter Editor TODAY'S NEWS Bruce's beak was injured during a fall as a fledgling, leaving his sharp lower beak exposed. Ximena Nelson Meet Bruce, a Kea parrot who is missing the upper half of his beak. He has turned this disability into a weapon to keep subordinates in line. | 3 min read  NASA's plan to land astronauts on the moon may be delayed because of lack of space suits. Development is behind and in danger of slipping further, according to a report from the agency’s Office of Inspector General. | 4 min read The FBI is investigating possible links between deaths and disappearances of at least 10 scientists. | 2 min read  For years, art historians believed the artwork The Baptism of Christ was likely painted by El Greco with assistance from other artists. But new research using AI suggests otherwise. | 4 min read The U.S. military will no longer require service members to be vaccinated against the flu, Secretary Pete Hegseth said today, drawing criticism from health experts. | 2 min read President Trump’s recent executive order to accelerate research on psychedelics for treating mental health could make it easier for researchers studying drugs like psilocybin, LSD and ibogaine. | 3 min read  Microgravity affects astronauts' motor skills, even after living at zero g for months. | 3 min read More News Science matters, don't you agree? Support science journalism you can trust with a subscription to Scientific American.  TOP STORIES Peptide Craze You may have seen posts or influencers on social media raving about the power of a particular peptide treatment for building muscles, getting younger-looking skin, or healing up fast from an injury. Despite the glowing reviews, most peptides have limited clinical evidence to support health benefits, and users have to order these injectables from sketchy online markets. In fact, in 2023 the FDA banned several peptides from being produced in the U.S. by compounding pharmacies (facilities that make non-FDA-approved medicines) because of safety risks.    The secretary of the Department of Health and Human Services, Robert F. Kennedy, Jr., has proposed legalizing the compounding of 14 peptides. And last week, the FDA released plans to review whether some U.S. pharmacies should be allowed to do just that.   I sat down with health editor Lauren Young to talk about the peptide craze.    Andrea Gawrylewski: Why have peptides become so trendy? You would think non-mandatory injectables would be scary to people, and yet these drugs have become so appealing.   Lauren Young: There are several things driving the peptide craze. One factor has been the rise of GLP-1 drugs. The increase in use has really normalized injectables. But perhaps the biggest, most obvious driver is the surge in high-profile influencers touting peptide “stacks”—essentially mixing and matching combinations of peptide injections to achieve personal health goals. Thousands of posts on Reddit and TikTok boast that peptides can quickly heal injuries, build muscle, clear up skin and reverse aging. All of those claims, none of which have been investigated thoroughly in clinical trials, are enticing to people who view these shots as quick “hacks” to better health. AG: "Peptides" sound like a natural remedy, but they are similar to classic drugs like insulin or semaglutide, which are also peptides. How does the "branding" affect the uptake of these substances? LY: The “natural” branding around peptide products evokes an image that they are somehow better or different from drugs. The term “drugs” also can have a negative connotation. Some might even think that “natural” also means safer or healthier. Journalist Bethany Brookshire, who wrote the story, explains that the peptides in this trend are derivations or synthetic versions of naturally occurring peptides. AG: Several of these peptides have been banned from being produced in the U.S. by compounding pharmacies. What are the main safety concerns of using peptides from other countries or the so-called gray market?   LY: Many of these products are not reviewed for safety or effectiveness by the FDA. And peptides that are approved are not being used as recommended. For instance, the “anti-aging” peptide GHK-Cu is an approved ingredient in topical cosmetics but is banned as an injectable because of safety risks such as immune reactions. The FDA is planning on creating a panel to review producing some peptides in U.S. compounding pharmacies. Even if those peptides are allowed to be made in the country, drugs from compounding pharmacies are still not reviewed for safety or effectiveness by the FDA.   Join the discussion: If the ban is lifted, would you be open to trying peptides to improve your health, regardless of the lack of scientific evidence supporting the health claims? Do you think a regulatory body should manage people's use of peptides? Weigh in by joining our online discussion here. INFOGRAPHIC OF THE DAY A sweeping new study found differences in numerous health conditions in firstborn children versus those born second. Researchers looked for 569 conditions across more than 10 million individuals and more than five million families. They found that firstborns are more likely to be diagnosed with neurodevelopmental conditions and allergies. Secondborns are more likely to get shingles or diagnosed with substance use disorder. Amanda Montañez; Source: “Birth Order and Disease Risk across the Human Phenome: Evidence from 10 Million Siblings,” by Benjamin Kramer et al. Preprint posted to medRxiv on March 27, 2026 (data)

PUZZLER This one's a doozy! Put your logic and arithmetic to the test with today's 6x6 KenKen puzzle: In this 6x6 grid, fill each row and column with numbers 1 through 6, while making sure the inner calculations are correct. For example in the top left box, the resulting computation should equal 2 and result from dividing one number by the other. More KenKen It bears repeating. If something seems too good to be true, it usually is. Just as you shouldn't trust any financial investment promises (like "guaranteed returns") or crazy discounts ($79.99 for a $1000 TV), beware overblown assurances around products to improve health. On top of the risk of draining your wallet, untested or nonregulated treatments can cause serious damage to your wellbeing.  Thanks for reading. Reach out to me anytime: newsletters@sciam.com. Until tomorrow!   —Andrea Gawrylewski, Chief Newsletter Editor

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