NASA file photo shows Expedition 50 crew as they pose for a portrait aboard the International Space Station. Photo: NASA

As humanity plans to soar out among the stars into the vast distances of space, the health effects of leaving the cradle of Earth continue to show consequences that are yet to be totally understood.

The latest look into the bodies of space travelers shows the levels of fundamental proteins change due to weightlessness, as reported by a Russian and Canadian team of scientists in the latest issue of the journal Scientific Reports

Essentially, it’s like the human body’s immune system fights the lack of gravity out beyond our world, they conclude.

“Weightlessness for humans is completely new in evolutionary terms, being an environmental factor our species has not faced during the course of evolution,” the team writes. “Our results support the hypothesis that adaptation to the conditions of space flight takes place in all of othe major types of human cells, tissues, and organs.”

Eighteen Russian cosmonauts on the International Space Station served as the subjects. The all-male group had a mean age of 44, and all were in space for 158 days (except for one, who spent 429 days aboard the ISS).

Their blood was drawn at three stages: 30 days before flight, within a day after landing, and a week after landing, according to the study.

The blood was scanned with multiple-reaction monitoring – mass spectrometry. A panel of 142 proteins previously noted in earlier research were compared along the timeline.

Concentrations of 19 of the proteins were changed by the trip – some quickly returning to normal, others taking longer. But none were permanently changed, they report.

“The results showed that in weightlessness, the immune system acts like it does when the body is infected because the human body doesn’t know what to do and tries to turn on all possible defense systems,” said Evgeny Nikolaev, a professor at Skoltech and the Mascow Institute of Physics and Technology, corresponding author of the study.

Other recent studies have indicated health effects brought about by long-term space exposure. In March, a Wake Forest Baptist Medical Center group of scientists found the combination of space radiation and weakened immune response meant a higher risk of certain cancers like leukemia. In 2015, a University of California Irvine group argued that the central nervous system itself could be significantly damaged during long-term travel through the vast distances of space.