The history of scientists conducting experiments on themselves is rich and significant. Such endeavors have led to critical advancements in medical science. One notable instance occurred in the early 1980s when Australian scientist Barry Marshall ingested a broth containing the bacterium Helicobacter pylori. His aim was to demonstrate that this bacterium, rather than stress, was responsible for stomach ulcers, a claim that eventually earned him a Nobel Prize. Similarly, Albert Hofmann famously dosed himself with LSD—first accidentally and then intentionally—after discovering the compound while seeking new medical treatments.

A 2019 study revealed that self-experimentation is still prevalent among researchers today. Out of 52 scientists surveyed, 26 acknowledged engaging in self-experiments, ranging from analyzing their own bodily fluids to trying experimental medications.

Brian Hanley, a co-author of the study and head of the biotech firm Butterfly Sciences, believes the actual number of self-experimenters is likely higher. He notes that many individuals involved in biological research, particularly those over 40, have engaged in such practices, often hesitating to admit it due to the stigma attached.

The motivations for self-experimentation are varied. They may include the desire to refine a technique for future applications, financial constraints that limit data collection through traditional means, the need to gather preliminary data in humans to ensure safety, or even the personal wish to benefit from a new treatment.

“Being the test subject allows for immediate troubleshooting if something goes awry before subjecting others to the same risks,” says one researcher.

As advancements in biomedical testing have made such processes more accessible and sophisticated, scientists have grown increasingly interested in understanding the intricacies of human biology on a daily and annual basis. However, expecting individuals to come to a lab for daily tests is often impractical, prompting some researchers to turn the focus onto themselves.

In 2009, Eric Alm and Lawrence David, then affiliated with MIT’s bioengineering program, contributed daily stool and saliva samples for an entire year to study their microbiomes. Reflecting on their experience, David remarked, “I was unsure I would last the year after the initial day—I nearly vomited.” Their commitment yielded insights into how diet, location, and bacterial infections can both temporarily and permanently alter the microbiome, illustrating that everyday life impacts this system significantly.

Stanford's Michael Snyder has taken self-monitoring to unprecedented levels. For over a decade, he has continuously assessed various biological markers, from his genome to the surrounding exposome. His goal was to explore how high-tech lab methods could be applied in clinical settings to better manage personal health. “I volunteered as the test subject to streamline the technology's application,” Snyder explains. Through this rigorous self-analysis, he uncovered critical health issues, including a significant genetic predisposition to Type 2 diabetes and early indications of Lyme disease.

Some researchers even self-administer treatments they have developed. The realm of anti-aging research is particularly rife with scientists who hope to personally benefit from their work. Mark Mattson, former chief of the National Institute on Aging's laboratory of neurosciences, has explored intermittent fasting and its health benefits for years, practicing the diet himself since his graduate studies in the 1980s. He found that skipping breakfast improved his efficiency and later extended the fasting regimen to investigate its effects on aging in animals, leading him to adopt a schedule where he consumes all his food within a limited timeframe. His findings suggest that this form of eating could enhance cognitive function and increase lifespan in mammals.

David Sinclair, co-director of Harvard Medical School's Center for the Biology of Aging, has a more elaborate approach to self-experimentation. He follows a daily routine of dietary supplements, including nicotinamide mononucleotide and resveratrol, compounds linked to delayed aging in mice. While his methods have drawn skepticism, Sinclair maintains that he does not profit from his discoveries nor presents his regimen as a guideline for others.

Self-experimentation raises ethical questions regarding bias and the integrity of results, especially when financial stakes are involved. The validity of findings from "n-of-1 studies" remains contentious.

Karen Maschke, a bioethicist at the Hastings Center, emphasizes the importance of established scientific protocols that ensure reliable data and reproducibility. “Self-experimentation can undermine the rigorous standards of scientific inquiry,” she cautions.

Safety is another significant concern; historically, eight scientists have died from their own experiments, typically due to self-inflicted diseases. One of the most notorious cases involved two researchers who allowed themselves to be bitten by mosquitoes carrying the yellow fever virus in 1900, resulting in one of their deaths.

All human subject research must undergo ethical reviews to ensure safety and informed consent, but there are no such requirements for self-experimenters—though many still seek ethical approval.

“It ultimately comes down to understanding the risks and ensuring safety,” Hanley asserts. “When you frame it as, ‘This is going into my body,’ caution becomes paramount.”

In a particularly audacious self-experiment, Hanley injected a gene into his cells to enhance growth hormone production in hopes of improving strength, stamina, and longevity. He utilized electroporation to facilitate the uptake of the new DNA into his muscle cells. Since undertaking this experiment, he has reported positive changes in various health markers but has hesitated to publish his findings due to concerns over safety and the potential for unintended consequences.

The rise of DIY science, especially around psychedelics and nootropics, underscores the need for caution. Some individuals are even conducting home gene editing experiments without professional oversight, which can lead to serious health risks. Dietary supplements lack rigorous safety testing, often containing undisclosed ingredients that may lead to adverse effects.

“This is serious business,” Hanley warns. “As the saying goes, if you’re not worried, you’re not paying attention.” It’s advisable to leave self-experimentation to trained scientists.