NASA’s space-grown lettuce richer in nutrients and safe for astronaut consumption

09 Mar 2020 --- The successful cultivation of red romaine lettuce on board the International Space Station (ISS) has been reported by researchers from the NASA Kennedy Space Center in Florida, US. Their research has revealed that despite being grown under lower gravity and more intense radiation than on Earth, space-grown lettuce is free of disease-causing microbes, safe to eat and at least as nutritious as Earth-grown plants. The researchers affirm that their results open the doors for subsequent experiments with other fresh, nutritious crops, as sustainable and safe food cultivation for crew consumption becomes more critical to NASA’s future extended space missions.

“The processed, freeze-dried, pre-packaged [space] diet is very nutritious, but over storage time, as you would need on a mission to Mars, vitamins and quality will degrade. We are looking at supplementing this diet with fresh produce that will provide nutrition and also add variety to the diet,” one of the study’s co-authors, Dr. Gioia Massa, Project Scientist at the NASA Kennedy Space Center, tells NutritionInsight.

Red Romaine lettuce can be successfully grown on board the ISS in outerspace. Source: NASABesides diet and menu variety, fresh produce would provide astronauts with additional potassium as well as vitamins K, B1 and C – nutrients that are less abundant in pre-packaged rations and tend to degrade during long-term storage. Likewise, the researchers also collected some evidence for space-grown lettuce being richer in sodium, phosphorus, sulfur and zinc, as well as in phenolics, molecules with proven antiviral, anticancer and anti-inflammatory activity. Both 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.

“The sample sizes were too small to determine whether the observed differences were due to spaceflight or natural variability. Plants might change their chemistry to respond to the space environment. Some of those chemical changes may protect the plants and could also provide more nutrients for humans,” Dr. Massa further explains.

No “significant differences” between space and ground crops
Between 2014 and 2016, NASA grew lettuce onboard the ISS from surface-sterilized seeds within Vegetable Production Systems, nicknamed “Veggie.” Specifically designed to grow crops in space, these growth chambers are equipped with LED lighting and a watering system. The crops grew undisturbed inside the Veggie units for 33 to 56 days until crew members ate part of the mature leaves. The rest was deep-frozen and transported back to Earth for chemical and biological analysis.

NASA astronauts Scott Kelly and Kjell Lindgren took their first bites on August 10, 2015.As a control, the scientists grew control plants on Earth under the same conditions as on ISS. The temperatures, carbon dioxide and humidity data logged onboard the ISS were replicated in the Kennedy Space Center’s laboratories with a 24 to 48-hour delay.

Dr. Massa affirms that lower gravity and more intense radiation have not proven to be significant challenges in terms of nutrient composition between space and Earth-grown crops. “We haven’t assessed the radiation impacts as the ISS remains within the Earth’s protective magnetic field much of the time. Microgravity primarily causes differences in water and air distribution within the root zone, which then can cause stresses of excess or insufficient water to the crops. Overall, we see increased microbiology on the space plants.”

Notably, tests confirmed that none of the detected bacteria genera growing on the lettuce – 15 microbial families on the leaves and 20 in the roots – are known to cause disease in humans or contaminate crops, such as coliform, E. coli, Salmonella and S. aureus. Meanwhile, the quantity of fungal and mold spores on the leaves was also in the normal range for produce fit for human consumption.

“Food safety concerns are a ‘worst case’ scenario [of space crop cultivation]. Keeping the astronauts safe and healthy from pathogens is our number one priority, and the goal is to ensure a safe food supply for terrestrial agriculture. Maintaining healthy plants without contamination and being able to detect any problems before they become hazardous are important areas for research and technology development both for Earth and space,” Dr. Massa underscores.

Veggie is the first fresh food production system delivered to the ISS. To tomatoes and peppers, and beyond!
Dr. Massa also regards this research as “early steps” while NASA works to develop space crop production to supplement the packaged diet. Growing leafy crops, such as lettuce, is the first stepping stone, as the researchers strive to add tomatoes, peppers, sweet potatoes and potatoes to the space diet. Crops that require more preparation and processing before cooking, like wheat and soybean, are not as likely to be integrated into the astro-diet in the near term, but these might be grown in more long-term outer-Earth scenarios, Dr. Massa affirms.

Plans for long-distance space missions include the upcoming Artemis-III missions scheduled to land humans on the lunar South pole by 2024 and NASA’s first crewed mission to Mars planned for the late 2020s. However, dining in space may not be limited to astronauts only. Growing popularity and demand for “astro-tourism” has also led space research to explore tasty and ergonomic eating experiences. Active in this area, Israel-based food company Aleph Farms is pushing food innovation boundaries with ISS-grown meat, what the company calls “a solution for preserving natural resources and reversing the climate change effects of factory farming.” 

“As we colonize space, we have to become less dependent on planet Earth. Plants may have a larger role in the food system, namely as aspects of a life support system where plants help recycle the atmosphere by taking up CO2 and giving off oxygen,” Dr. Massa concludes. 

By Anni Schleicher