Strange Space Phenomena Revealed

Astronauts returning from extended missions aboard the International Space Station have shown measurable changes in their gut microbiomes, with certain beneficial bacteria decreasing and potentially harmful strains increasing, according to a new study published in the journal Microbiome on April 15, 2026.

The research, conducted by scientists at NASA’s Johnson Space Center in collaboration with the Baylor College of Medicine, analyzed stool samples from 11 astronauts who spent between six and twelve months in microgravity. Samples were collected before launch, during the mission, and after return to Earth, allowing researchers to track shifts in microbial composition over time.

Results indicated a consistent reduction in diversity of the gut microbiota during spaceflight, particularly a decline in species known to support immune function and metabolic health, such as Faecalibacterium prausnitzii and Eubacterium rectale. At the same time, there was a relative increase in bacteria associated with inflammation and gastrointestinal stress, including certain strains of Enterobacter and Streptococcus.

Lead author Dr. Hernanda Wijaya, a microbiologist at the Universities Space Research Association, explained that the changes appear linked to multiple factors unique to the space environment, including altered diet, stress, disrupted circadian rhythms, and the effects of microgravity on gastrointestinal motility and fluid distribution.

“We’re not seeing pathogenic outbreaks or acute illness in astronauts, but the microbiome shifts we observe are consistent with patterns seen in inflammatory bowel disease, metabolic syndrome, and chronic stress conditions on Earth,” Dr. Wijaya said. “This raises concerns about long-term health risks for astronauts on future deep-space missions, such as those planned to Mars.”

The study also found that while some microbial changes reversed within weeks of returning to Earth, others persisted for months, suggesting that recovery may not be complete or immediate. Researchers noted that individual responses varied significantly, with some astronauts showing greater resilience in their microbial communities than others.

To counteract these effects, NASA is currently testing targeted probiotic formulations and prebiotic dietary supplements in ground-based analogs, such as the HERA (Human Exploration Research Analog) habitat. Early results from a parallel study showed that astronauts who consumed a specific blend of Bifidobacterium and Lactobacillus strains maintained higher microbial diversity during simulated spaceflight conditions.

Experts caution that while the findings are significant, the study’s small sample size limits broad generalizations. They emphasize that microbiome research in space is still emerging, and longer-duration studies with larger crews will be needed to confirm trends and assess clinical relevance.

Nevertheless, the results underscore the importance of monitoring gut health as part of astronaut medical protocols. As space agencies prepare for missions beyond low Earth orbit, understanding and mitigating microbiome disruption may become a critical component of ensuring crew health and mission success.