There’s been a lot of excitement about the potential possibility of long-term, long-distance space travel in the coming years and decades. Concerns have been raised about the health effects of these kinds of trips, however, especially regarding issues like interplanetary radiation levels and long-term zero gravity. Some new research from McGill University, however, has revealed an unexpected potential issue: the intestinal bacteria in the “gut biome.”
SpaceQ reached out to a lead researcher on the project, McGill University Microbiome Research Center’s Emmanuel Gonzalez, to find out more about the situation.
The gut biome and health
Many (even most) people probably don’t even realize that the gut biome is a thing, especially as we generally think of bacteria ending up in our body as a bad thing. They’re absolutely necessary, though; humans (and many other animals) cannot digest many foods (even most foods) that we need to survive without having a variety of different kinds of bacteria help in the process. This is why humans burp and pass gas; the bacteria in our digestive tract will create methane and other gases in the process of breaking down these foods to forms that we can digest.
An enormous number of these beneficial bacteria are found in our digestive systems, and disruptions to those internal ecosystems— such as when people take antibiotics to get rid of harmful bacteria in other parts of our bodies—can have serious effects on people’s health in a variety of unexpected ways. Dr. Gonzalez said that “when this delicate ecosystem is disrupted, it can lead to problems like poor digestion, inflammation, and even higher disease risk.”
Gonzalez also pointed to how it can even affect our mental health. He said “the gut is also connected to the brain in a relationship often referred to as the ‘gut-brain axis.’ In short, the health of our microbiome can even affect our mood and mental health, highlighting its importance for both physical and mental well-being.”
A potential explanation for astronaut health issues
Gonzalez has a background in computational science and bioinformatics, and was drawn into space biology because “in space biology, the high-throughput data generated from microbiome sequencing needs sophisticated analysis pipelines”. His knowledge of bioinformatics “has been crucial for interpreting this data, enabling us to uncover subtle changes in microbial ecosystems, even in extreme environments like space”.
Gonzalez said that he and key partners, biologists Nicholas Brereton and Fred Pitre, began working together at the Montreal Botanical Garden on “developing techniques to analyze microbiomes in spaceflight conditions.” Their research eventually attracted the attention of NASA’s GeneLab, and they “became part of an international team focused on space biology research.”
This work on microbiomes led them to start thinking about whether and how the gut biome might help explain some health issues that are being routinely seen in astronauts. Issues like “insulin resistance, high cholesterol, and gut inflammation,” he said, were ones that may be related to changes in the gut biome.
So, in conjunction with University College Dublin (UCD) and their partners at GeneLab, they set out to study how the gut biome functioned in space. Over time, “more researchers joined the project,” he said, “making it a truly collaborative effort.”
While the issues they were studying were found in human astronauts, Gonzalez said that their experiment focused on using mice instead. He said that there simply haven’t yet been enough humans in space simultaneously to be able to study the issue properly and scientifically, so mice can serve as a substitute. “While the specific bacteria found in mice may differ from those in humans, the functions they perform can be quite similar,” he said, allowing them to “infer how these systems might behave in humans.”
They studied three different groups of mice; one set here on earth, the others in the International Space Stations’s (ISS) dedicated rodent habitat. One group returned after 29 days to be examined, and the third, he said, “stayed on the ISS for 56 days,” and then examined in space. This allowed them to compare exposure over time, and compare the space mice to the earth-based controls.
Observing “significant shifts” in the biome
Previous studies, Gonzalez said, “didn’t find much difference,” and so they “weren’t expecting drastic changes.” Drastic change, however, was what they found.
Gonzalez said they discovered “significant shifts in the gut microbiome” of the orbital rodents, which were “more extensive than we expected,” Several bacterial species were much less abundant, he said, including bacteria that were “important for processes, like butyrate production, which helps maintain gut health and regulate metabolism.” These changes correlated with changes in the hosts’ energy metabolism and immune response capabilities, and matched some of the issues that had been seen in astronauts.
Gonzalez did not believe these changes could be attributed to one specific factor, like microgravity or diet, at least not without more controlled experiments that isolate specific effects. What he did note, however, was that studies based on the “Mars 500” experiment, where participants were isolated in a bunker for an extended period, “experienced similar disruptions in their microbiome, despite not being in space or exposed to microgravity.” Gonzalez said that this “aligns with the broader understanding that environmental stressors can disrupt microbial balance.”
Their study also showed that these changes took place relatively quickly, at least in the mice. Similar changes were seen in both the short-term and longer term experimental groups, though he noted that “interestingly, we didn’t see much difference” between the two groups. That suggests, to Gonzalez, that “these disruptions occur within the first few weeks.” More research will be needed to precisely understand how soon the changes begin, and how they could evolve over longer periods of time. More research will also be needed to understand exactly how this applies to human gut biome changes.
A potential problem for humans in space
The Mars 500 experiment suggested that these kinds of changes would be slower in humans, taking place over months. Gonzalez believes that “it’s reasonable to predict that similar changes could manifest in human astronauts over time,” cautioning that “the speed and nature of the disruptions could differ due to species-specific factors and environmental conditions.”
But these issues could be a serious problem in the future, both in spaceflight and in outer-space habitation. He said maintaining astronaut health during long-distance space travel is a “major concern,” and that disruption to the gut microbiome could lead to metabolic problems and insulin resistance. He particularly highlighted immunity issues as a potential concern, saying that “the results showed that spaceflight led to a suppression of important immune pathways.”
In space, these issues would be added to other, well-known health health issues: like radiation, microgravity, and various psychological stressors. Even on lunar or planetary habitats where microgravity and radiation (theoretically) less of a concern, however, the issue of gut biome changes could be one that we’ll be grappling with. The issue of harmful microorganisms and pathogens could also be a serious issue, especially if regular immune function has been disrupted.
Probiotics in space?
When asked about steps to be taken, however, Gonzalez did point to some possibilities. He noted that their current research is now focused on how to “maintain a balanced ecosystem in space habitats,” and a major focus of that research is “exploring the interactions between diet, gut health, and the broader environment.” In particular, they’re looking at the effect of diet on gut inflammation, which he described as “critical for understanding how astronauts’ health can be supported over long-term missions.”
Food is a major focus. They’re working with Montreal’s General Hospital and international partners on “studying the relationship between diet and chronic pain conditions, which could have significant implications for long-duration space travel.” Part of that research, Gonzalez said, is “examining the microbiomes of the Axiom One passengers—the first private astronauts to travel into space,” which will “give us insights into how short-term and long-term space stays affect the human microbiome and overall health.”
They’re also working with GeneLab and other partners (like Brereton and Pitre) to study plants in space, which will not only potentially serve as a comparatively healthy food source, but as “part of the ecosystem that supports human health.”
As to more direct dietary interventions to aid the gut biome in space, Gonzalez said that “we don’t have a definitive answer yet.” Probiotics that introduce healthy bacteria are one possibility, but he said that “we could also consider prebiotics, which feed the beneficial bacteria already present in the gut, or postbiotics, which are the by-products of bacterial activity and could also have health benefits.”
He granted that these interventions are “promising”, but cautioned that “space is such a unique environment that we need more research to determine whether they would have the same positive effects as they do on Earth.” He added that “what works well here might not have the same impact up there.” The research continues.