Scientists have now confirmed that the red romaine lettuce grown on the International Space Station in 2014 through 2016 is as healthy and nutritious as Earth-grown lettuce. The experiment and subsequent confirmation comes at an ideal time for NASA as the possibility of growing crops onboard a spacecraft opens the door to long-duration missions beyond low-Earth orbit, like those to Mars or the lunar South pole.
While astronauts, including the famed Scott Kelly, were growing lettuce onboard the ISS from surface-sterilized seeds within Vegetable Production Systems, scientists at the Kennedy Space Center on Earth were cultivating control plants under the same conditions. After ISS crew members ate part of the mature leaves of the lettuce, they deep-froze the rest to send back to Earth for chemical and biological analysis.
In a paper published in Frontiers in Plant Science, researchers confirm that space-growth lettuce has a similar composition to the Earth-grown controls, except that some space-grown plant tissue was richer in elements such as potassium, sodium, phosphorus, Sulphur and zinc, as well as phenolics, or molecules with proven antiviral, anticancer and anti-inflammatory activity. Space- and Earth-grown lettuce also had similar levels of anthocyanin and other antioxidants, which can protect cells from damage by free, reactive oxygen radicals.
Researchers did find something unexpected when they examined the microbial communities of both the space- and earth-grown plants. Typical Earth-grown plants have a diverse set of microbes that can affect the health of the plants and their suitability as a food course. Considering how and where the space-lettuce was grown, scientists expected to see distinct microbial communities. However, next-generation DNA sequencing identified 15 of the most common Earth-microbial genera on the leaves and 20 in the roots, and found that the diversity resembled Earth-grown lettuce to a remarkable amount.
Beyond the unexpected results, none of the bacteria genera identified are known to cause disease in humans, and further tests confirmed the space-grown leaves never carried dangerous bacteria, such as E.coli.
Currently, astronauts in space live on pre-packaged rations that have been sterilized and freeze-dried to ensure longetivity. Not only is the taste lacking, but so are common nutrients found abundantly in food not intended for long-term storage. Fresh produce grown in space would provide astronauts with additional potassium as well we vitamins K, B1 and C. This is despite being grown in lower gravity and under more intense radiation than on Earth.
“The International Space Station is serving as a test bed for future long-duration missions, and these types of crop growth tests are helping to expand the suite of candidates that can be effectively grown in microgravity,” said study co-author Gioia Massa, project scientist at Kennedy Space Center. “Future tests will study other types of leafy crops as well as small fruits like pepper and tomatoes, to help provide supplemental fresh produce for the astronaut diet.”
Photo: NASA astronaut Shane Kimbrough during the first harvest of Outredgeous Red Romaine Lettuce from the Veggie facility during VEG-03. Credit: Kimbrough/NASA