People are changing their microbiomes just by spending more time in nature
In the galleries of a Denver museum, a genomics scientist found that the invisible microbial communities living inside the human nose quietly record our relationship with the natural world — and that this record correlates with the state of our minds. Bridget Chalifour's study of 111 museumgoers suggests that time spent outdoors does not merely refresh the spirit in some poetic sense, but may reshape the body's microbial landscape in ways that measurably reduce depression. The finding reframes an ancient intuition — that nature heals — as a biological process, one in which the act of going outside matters more than the mere proximity of green.
- Researchers discovered that people who spend more time outdoors carry a richer, more diverse community of microbes in their nasal passages — and report better mental health.
- Living near green space alone offered limited benefit; the critical variable was whether people actually stepped outside and stayed there.
- Some of the same microbial species elevated in outdoor-active participants also appeared at higher levels in those with lower depression scores, suggesting a biological link rather than coincidence.
- The nasal microbiome appears to be dynamic and behaviorally responsive, shifting its composition based on environmental exposure — a finding that could reframe how we understand nature's effect on mental well-being.
- The study, conducted at the Denver Museum of Nature & Science using participant-collected nasal swabs and satellite-mapped green space data, marks an early but significant step into microbiome research for the institution.
A genomics scientist at the Denver Museum of Nature & Science has uncovered something unexpected in the noses of ordinary museum visitors: evidence that time spent outdoors reshapes the microbial communities living there, and that these changes correlate with measurable improvements in mental health.
Bridget Chalifour led a study inviting 111 museumgoers to contribute nasal swabs and answer questions about their well-being, outdoor habits, and pet ownership. Using genetic sequencing, researchers mapped the microbial landscape inside each participant's nose, while earth scientists pulled satellite data to measure the vegetation surrounding each person's home.
A clear pattern emerged. People living near more greenery hosted greater microbial diversity in their nasal passages. More striking, some of the same microbes found in higher numbers among frequent outdoor visitors also appeared elevated in those reporting better mental health scores. "We tend to associate greater diversity and greater richness with a healthier microbiome," Chalifour noted.
The study also revealed a hierarchy of influence. Time spent outside proved more consequential than proximity to green space alone — someone living beside a park but rarely venturing out saw little benefit, while those who regularly spent hours in nature showed lower depression scores regardless of their neighborhood's greenery. "Time was really important in all aspects," Chalifour said.
The findings point toward something dynamic: the nasal microbiome appears to respond to behavioral choices, shifting in composition as our habits change. This responsiveness may help explain why time in nature so consistently lifts mental health — the answer, it seems, may be carried in the invisible microbial passengers we host in our own noses.
A genomics scientist at the Denver Museum of Nature & Science has found something unexpected in the noses of museum visitors: evidence that time spent outdoors reshapes the microbial communities living there, and that these changes correlate with measurable improvements in mental health.
Bridget Chalifour, a principal investigator at the museum, led a study that invited 111 museumgoers to contribute nasal swabs and answer questions about their mental well-being, outdoor habits, and pet ownership. The museum's genomics lab, visible to visitors through glass walls, became the site of a straightforward experiment. Participants swabbed their own noses—a skill many had refined during the pandemic—and researchers used genetic sequencing to map the microbial landscape inside them. Meanwhile, the museum's earth scientists pulled satellite data to identify how much green space surrounded each participant's home address.
What emerged from the analysis was a pattern. People living in neighborhoods with more vegetation hosted a greater variety of microbes in their nasal passages. More striking still, some of the same microbes that appeared more frequently in people who spent significant time outdoors were also present in higher numbers among those reporting better mental health scores. The connection was not incidental. "We tend to associate greater diversity and greater richness with a healthier microbiome," Chalifour explained. The data suggested that exposure to nature was actively shaping the microbial composition of the human nose in ways that seemed to matter for psychological well-being.
But the study revealed a hierarchy in what actually drives these changes. Time spent outside proved more influential than proximity to green space alone. A person could live next to a park and see minimal benefit if they rarely ventured out. Conversely, someone spending regular hours in nature—whether in a verdant neighborhood or a less obviously green one—showed lower depression scores and a more diverse nasal microbiome. "Time was really important in all aspects," Chalifour said. The implication was clear: the act of going outside mattered more than the accident of geography.
The findings suggest something more dynamic than a simple correlation. The nasal microbiome appears to respond to behavioral choices, shifting its composition in response to environmental exposure. This responsiveness may help explain a puzzle that has long intrigued researchers: why does time in nature so consistently improve mental health? The answer may lie partly in the invisible passengers we carry in our noses, communities of microbes that change when we change our habits. "People are changing their microbiomes just by spending more time in nature," Chalifour observed. The museum's work represents an early step into microbiology for the institution, though it has long maintained a tradition of rigorous scientific research across multiple disciplines. The nasal microbiome, it turns out, was waiting to be studied all along.
Notable Quotes
We tend to associate greater diversity and greater richness with a healthier microbiome— Bridget Chalifour, genomics scientist
People who spent more time outdoors, regardless of how green it was, had lower depressive scores overall— Bridget Chalifour
The Hearth Conversation Another angle on the story
Why focus on the nasal microbiome specifically? Why not study the gut, which gets so much attention?
The nose is where the outside world first meets your body in a sustained way. You're breathing in particles, microbes, everything from the environment. The gut microbiome has been studied extensively, but the nasal one was genuinely overlooked—a gap in the research.
So the study shows that being outside changes which microbes live in your nose?
Yes, and not randomly. People who spend more time outdoors host different microbial communities than those who don't. The diversity increases. And some of those same microbes correlate with better mental health scores.
Is it the microbes causing the mental health improvement, or is something else happening?
That's the honest answer: we don't know yet. The study shows correlation, not causation. But the fact that the microbiome composition shifts in response to outdoor time suggests the microbes might be part of the mechanism, not just passengers.
The study found that time outdoors mattered more than living near green space. That's counterintuitive.
It is. You'd think living surrounded by nature would be enough. But the data says you have to actually engage with it. A person in a concrete neighborhood who spends hours outside regularly shows better outcomes than someone living next to a park who rarely leaves home.
What happens if someone starts spending more time outside? Do their microbiomes shift quickly?
The study doesn't track that over time, so we don't know the timeline. But the implication is that the change is responsive—your nose is listening to your behavior.