Norishige Kanai, who claimed to grow 3.5 inches taller after three weeks on the International Space Station, has retracted his previous statement by apologizing for the "fake news."
The Japanese astronaut reports the growth spurt in a tweet posted last Monday, where he even joked about becoming too tall to fit inside the Soyuz spacecraft on his trip back to Earth.
While it is true that microgravity environments cause the spine to decompress resulting in a temporary height increase, NASA says humans would only be able to grow taller by a maximum of two inches.
This made a Russian colleague dubious of the growth spurt. As suggested by the cosmonaut, Kanai double checked his body measurement and discovered he made an error. His growth spurt did not even exceed an inch as he had only grown by 0.78 inches.
"I am very sorry to spread such fake news," he writes in a follow-up tweet on Tuesday. "I am a little relieved to be able to ride on the return Soyuz."
Effects Of Microgravity On The Human Spine
In response to social media users asking if he feels any pain due to spine elongation, Kanai assures he has not experienced any on either of his back or hips and that the stiffness around his shoulders had already disappeared.
According to NASA, this growth spurt does not necessarily pose any major health risks. All six astronauts in the Skylab missions exhibited a 3 percent height increase while in space but as soon as they were exposed to regular gravity, their spines returned to normal within 10 days.
The extra height would only be a problem if crew members outgrow their custom-fitted pressurized suits, which they wear when launching or landing. Additionally, Kanai's worries were indeed legitimate as the Soyuz has a certain height limit.
"The spine is compressible, so astronauts might be able to squish to fit in, but if it's a tight fit to begin with, it might be too tight," says Dr. Sudhakar Rajulu, a researcher at Johnson Space Center's Habitability and Environmental Factors Office.
The Twins Study: One Year In Space Changes Genome Sequencing
Aside from adding extra inches to a person's height, spending time in microgravity environments can ultimately change a person's DNA and RNA. This was proven by NASA's Twin Study, which studied identical twin brothers and astronauts Scott and Mark Kelly to identify the long-term effects of space travel on the human body.
Preliminary results reveal that Scott's telomeres, or the caps found at the end of chromosomes, grew longer than his brother's. Likewise, DNA methylation which controls gene expression was found to have decreased in Scott and increased in Mark over the same duration. Upon their return to Earth, Scott's telomeres quickly returned to its normal length and DNA methylation in both men also returned close to their pre-flight levels.
Scientists have yet to determine the implication of these changes but they have been found to occur even in humans on Earth. They have been linked with environmental shifts, particularly with changes in sleeping and eating habits.
Final results of the Twins Study will allow development of personalized medicine to keep astronauts healthy during long-term space missions, such as NASA's planned trips to Mars.