Space and Physics
PUBLISHED
In space, nobody can hear you scream. Which is a good thing, when everybody is apparently quite constipated and occasionally experiencing "wet burps".
A new collaboration between NASA and the University of Copenhagen has taken a look at the gastrointestinal issues of astronauts, finding potential causes for their tummy issues.
Humans have evolved here on Earth, where gravity is (roughly speaking) a solid and comfortable 1G ( an acceleration rate of around 9.81 meters per second squared). When we first began to investigate firing up a rocket and leaving the Earth to explore space, it wasn't clear that all of our biological activities would continue as normal without gravity to assist us.
Eating in space
Thankfully, this was soon cleared up with a few tubes of meat paste, a tube of chocolate paste, and some apple sauce.
"Before food was first consumed in the space environment, it was assumed by some that the greatest challenge of providing food in space might well be that a human would be unable to swallow and thus would be unable to eat in weightlessness," a NASA document explains.
"This was quickly disproved by Soviet cosmonaut Gherman Titov, who in August 1961 became the first human to consume food in space. U.S. astronaut John Glenn followed closely when, as the first American to consume food in space, he ate applesauce on the third manned Mercury mission in February 1962."
Humans can eat in space. Hell, we've even had barbeques. The first parts of the eating process are actually relatively unaffected by a lack of gravity, with the muscles in your esophagus pushing the food down nicely into your stomach.
But when the food reaches the stomach, things do get a little messy without enough gravity to assist.
Pooping in space
"In the microgravity environment of space, fluids in the body tend to shift and redistribute upwards," NASA explains. "The contents of the stomach are free to float, while the intestines are less densely packed together. The body relies completely on peristalsis to move food through the digestion tract without the aid of gravity."
One of the results is that astronauts experience "wet burps" with food taking longer to settle down, and taking longer to make its way out of an astronaut, compared to when they are on Earth.
In a new study, researchers investigated changes to digestion, looking at blood samples collected from 52 astronauts. The team found that key gastrointestinal changes took place shortly after astronauts enters a microgravity environment.
"We see changes in astronauts’ blood samples that indicate that the gut bacteria begin to ferment protein to a greater extent than usual within weeks after the astronauts arrive in space, and this change continues until they are back on Earth," Giorgia La Barbera, the joint first author and associate professor at the Department of Nutrition, Exercise and Sports, explained in a statement.
On Earth, gut bacteria can begin to ferment protein too, once fiber in your diet has been used up. In space, however, it appears to be more common.
"The lack of gravity in space probably causes food to move more slowly through the intestine, and this fits with the fact that we are seeing signs of increased protein fermentation," co-author Henrik Roager, also an associate professor at the Department of Nutrition, Exercise and Sports, added.
"This may also help explain constipation in astronauts."
Long-distance space squits
Constipation during spaceflight may be uncomfortable, but more worrying are potential long-term health issues with protein fermentation, including effects on focus, mood, and potential kidney damage. This could cause issues on longer spaceflights, for example if we were to attempt to land humans on Mars.
On such missions, extra precautions may be necessary to keep everyone healthy and unconstipated.
"Our findings can inform potential interventions – either directly through increasing dietary fiber, supplementation with prebiotics or other types of treatments that promote peristalsis and decrease gut transit time," Roager added.
"This would help reduce protein fermentation and thus provide a healthy gut environment and avoid negative health consequences."
As well as helping astronauts as they head to other celestial bodies, or an orbiting space station, the research could potentially help bed-ridden patients, whose problems may also be compounded by protein fermentation, according to the team.
The study is published in Nature Communications.
