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Space poses some massive dangers for humans, from black holes to the heat death of the universe. But as humanity considers long-haul space travel, there are other, smaller potential hazards that some researchers say may deserve more attention: microbes from Earth.

Astronauts face numerous known health problems in space, including a loss in bone density, muscle atrophy, and psychological issues . And on Earth, researchers are increasingly discovering how the various bacteria and other microorganisms that live inside and outside of people — the human microbiome — affect physical and mental health .

Space, of course, is an entirely different environment from Earth, with high radiation levels and microgravity. Although the science is far from certain, these vast differences may cause unexpected changes in the microbiome of astronauts. In turn, this could result in a range of health problems, which may be more pronounced on long-haul stints in space, like traveling to another planet.

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When you hear about the gut microbiome, does it ever make you wonder what tiny creatures are teeming inside your own body? As a microbiologist who studies the microbiomes of plants, animals, and people, I’ve watched public interest in gut microbes grow alongside research on their possible dramatic influence on human health. In the past several years, microbiome testing techniques used by researchers like me are now available to consumers at home . These personal gut microbiome testing kits claim to tell you what organisms live in your gut and how to improve your gut microbiome using that data.

I became very interested in how these home test kits work, what kind of information they provide, and whether they can really help you change your gut microbiome. So I ordered a few kits from Viome, Biohm, and Floré, tried them out, and sifted through my own microbiome data. Here is what I learned.

How do gut microbiome kits work?

All gut microbiome kits require you to carefully collect fresh fecal material. You put it in the various tubes provided in the kit and mail the samples back to the company. Several weeks later, you’ll receive a report describing the types of microbes living in your gut and suggestions on how to change your diet or activities to potentially alter your gut microbiome.