While in zero gravity, an astronaut’s bone density can drop by an average of one to two percent every month. During short-term missions to the International Space Station (ISS), the bone mass loss may not be as severe. However, during long-term missions to the moon, Mars and beyond, spacefarers will need a way to keep their skeletons in shape—and it could be as easy as eating a salad.
A team of researchers at the University of California, Davis, have developed modified transgenic lettuce that produces a bone-stimulating hormone. The lettuce can be easily grown in space and could help strengthen an astronaut’s bones. It may even help reduce the risk of osteoporosis on Earth in areas with limited sources, according to a statement. The study’s findings were presented during the American Chemical Society (ACS) Spring 2022 Meeting.
“Right now, astronauts on the International Space Station have certain exercise regimens to try to maintain bone mass,” says Kevin Yates, a graduate student and chemical engineer at the University of California, Davis, in a statement. “But they’re not typically on the International Space Station for more than six months.”
Restoring bone mass currently requires an injection of medication containing a peptide fragment of human parathyroid hormone (PTH) used to stimulate bone formation, reports Ellen Phiddian for Cosmos. Because the medication needs to be injected daily, this method of replenishing bone loss is not feasible for long-term space missions.
So, scientists decided to see if they could produce a modified strain of lettuce containing the medicines that would grow in space. Researchers chose to focus on lettuce because the plant has been grown numerous times aboard the International Space Station (ISS). As an added benefit, the leafy greens would provide a way for astronauts to eat veggies that are fresh instead of freeze-dried and canned.
“Astronauts can carry transgenic seeds, which are very tiny — you can have a few thousand seeds in a vial about the size of your thumb — and grow them just like regular lettuce,” says Somen Nandi, a collaborator on the research and chemical engineer at UC Davis, in a statement. “They could use the plants to synthesize pharmaceuticals, such as PTH, on an as-required basis and then eat the plants.”
To create the modified lettuce, the team identified the genetic code for a version of PTH that included another protein that would make it easier for the human body to absorb, Cosmos reports. Scientists then transferred this gene into lettuce plants using a bacteria called Agrobacterium tumefaciens.
After the lettuce grew, the team screened the plants for the hormone and found that the lettuce produced between 10 to 12 milligrams of the protein per kilogram. For astronauts to get enough of the hormone, they would have to eat 380 grams, or 8 cups, of lettuce a day—about the equivalent to a heaping bowl of salad, per Cosmos.
Researchers plan to improve the hormone content next, find an easier way to administer it and test how it will grow on the ISS. The lettuce will need to undergo animal and human trials to ensure the lettuce is safe to consume and actually stimulates bone growth. The greens haven't been taste-tested for flavor yet either.
Still, the study shows how medications can be grown in outer space, which can cut costs and avoid damages caused by radiation. Mars missions that can take approximately three years to run would be difficult to resupply. Even if supply drops are scheduled ahead of time, years of radiation may render the medications unusable, reports Leto Sapunar for Popular Science.
“I would be very surprised if, by the time we send astronauts to Mars, plants aren’t being used to produce pharmaceuticals and other beneficial compounds,” Yates says in a statement.