NASA and University of Copenhagen study links microgravity to astronaut constipation

A collaborative study by the University of Copenhagen and NASA has identified potential biological reasons for the frequent occurrence of constipation among astronauts in space. By analyzing blood metabolites from 52 astronauts who spent between two and nine months aboard the International Space Station, researchers found significant changes in how gut bacteria process food.

The study, published in Nature Communications, suggests that microgravity may slow the movement of food through the intestines. This slower transit time appears to encourage gut bacteria to engage in increased protein fermentation. While bacteria typically prioritize dietary fiber, the lack of gravity may allow them more time to break down proteins once available fiber is exhausted. These elevated levels of protein fermentation were observed within weeks of entering space and persisted until the astronauts returned to Earth.