No booze in space: The sobering effects of spaceflight on the liver

In the decades since the start of the space race, living in space has become at least a little more comfortable. Astronauts have been living on the International Space Station continuously for more than 20 years, and that’s difficult to do without having at least some of the amenities we’re used to at home.

Engineers and corporations, in collaboration with space organizations, have found a way to improve entertainment and even deliver food to astronauts living in low-Earth orbit, but there might be some limitations as to what’s possible or healthy for spacefarers to consume off-planet. While you might be able to get a pizza delivered to your orbiting laboratory, having a beer to go with it might be beyond our reach. And it’s all thanks to the effects of microgravity and radiation.

A recent paper by a team of scientists from the Microalgae Production Control Technology Laboratory at RIKEN, the Faculty of Life and Environmental Sciences at the University of Tsukuba, and colleagues, reveals that space travel has a deleterious impact on the liver. Their findings were published in the journal Scientific Reports.

It’s no secret that long-term space travel can cause physiological changes in astronauts ranging from chronic congestion to distorted vision and bone loss. There have even been hints that the liver might be impacted, but new research outlines the mechanisms present in space-based liver damage for the first time.

Researchers worked with the Japan Aerospace Exploration Agency (JAXA) to fly a group of mice to the International Space Station (ISS), where they lived for 30 days. The moustronauts were broken into two groups, one of which experienced normal microgravity for the duration of their stay aboard the station, while the other was provided with artificial Earth gravity by way of cages mounted to a centrifuge. A third group remained on Earth where they served as a control. Ground control, if you like.

For the control group, efforts were made to mimic the conditions on the station as closely as possible, aside from the relevant space-based variables. Mice were provided the same diet and kept in the same cages.

Scientists were looking specifically at sulfur-containing compounds in the liver to quantify how they are affected by higher exposure to radiation and microgravity apparent during space travel. Ongoing research on Earth suggests that changes to sulfur-containing amino acids contribute to the development of liver disease, so changes to those compounds in space could be an indication of heightened risk of liver disease for astronauts.

After 30 days had elapsed, the mice were returned to Earth, where their livers were examined and compared to the control group. Researchers confirmed that both ISS groups exhibited a decrease in sulfur-containing antioxidants and their intermediates in the liver, when compared to the control group. Moreover, the liver appears to be impacted by the conditions of space travel more heavily than other organs, a considerable problem considering the vital role the liver plays in the body.

A difference was apparent in both groups, though some of the compounds decreased only in mice who experienced microgravity while remaining at normal levels in those who were in the centrifuge cages. This indicates that at least some of the negative effects can be mitigated by the institution of artificial gravity.

The remainder of the decrease, however, might be driven by heightened exposure to radiation while in space, something which is a little more difficult to control. Scientists are hard at work on new, and sometimes bizarre strategies for reducing the risk of radiation in space.

While we’re working on better radiation shielding, researchers suggest that supplements might help close the gap in the meantime. The negative effects on the liver could be mitigated by the consumption of sulfur compounds, specifically GSH, ergothioneine, and taurine, during and after spaceflight.

Experiments on Earth have shown that oral administration of those compounds can protect against liver damage in humans. The beer manufacturers of the future might need to brew up specialized supplemented ales if astronauts want to feel a little floaty while they’re floating.

Let’s hope they figure it out before too long. Being an astronaut can be stressful and they deserve a break as much as anyone. It’s a long trip to Mars without a happy hour every now and then.