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ISS astronauts eating lettuce in space

‘Awesome’ space lettuce is safe to eat, Nasa declares

Image credit: Nasa

Lettuce lovingly grown by Nasa astronauts on the ISS has been found to be just as safe and nutritious as lettuce grown on Earth.

Space agencies hope to send astronauts to Mars and other alien territory in the coming decades, although serious practical barriers remain, such as keeping astronauts healthy for long-duration missions.

Nasa and other space agencies have been investigating the feasibility of growing fresh food in space, where plants experience very different environmental conditions, such as higher levels of radiation and reduced gravity.

A Nasa experiment to grow lettuce in space has now published its promising results, long after the plants were originally grown between 2014 and 2016.

The experiment involved planting sterilised seeds in individual sealed units of clay substrate and fertiliser in the ISS’s 'Veggie' plant growth chamber, a specialised potting chamber launched to the ISS in 2014. The chamber illuminated the crops with red-pink LED lights and injected water directly into the pillows.

The lettuce was grown in the chamber between 33 and 56 days, while control crops were grown under similar conditions on Earth, replicating the humidity, carbon dioxide concentration and temperature experience by the plants in the ISS.

Once the plants were fully grown, they were harvested and either sanitised and eaten, deep frozen or returned to the Kennedy Space Centre for analysis. Tasting the lettuce for the first time, the ISS astronauts described it as “awesome” and “fresh”.

Nasa scientists carried out an extensive series of examinations and found that the space lettuce is similar in composition to the control lettuce grown on Earth.

Some of the plants grown in the ISS were richer in potassium, sodium, zinc, phosphorous, sulphur and phenolics (a group of compounds with antioxidant properties). The space lettuce carried similar bacteria to the lettuce grown on Earth: this was not expected, given that the ISS has a distinct bacterial ecosystem. Although the lettuce had higher levels of bacteria, they did not carry any bacteria which could cause sickness, such as salmonella, staphylococcus aureus or E.coli. Fungus and mould spores were found to be within the safe range for human consumption.

“This study indicated that leafy vegetable crops can produce safe, edible, fresh food to supplement the astronauts’ diet,” concluded the Frontiers in Plant Science report.

Since 2016, other vegetables have been grown on the space station.

“The ability to grow food in a sustainable system that is safe for crew consumption will become critical as Nasa moves toward longer missions,” said Christina Khodadad, study author and Kennedy Space Centre researcher.

The ability to grow food in space will be crucial for sustaining astronauts on long-duration missions which require them to be almost 'Earth independent'. Processed, dried, pre-packaged foods consumed by astronauts have been found to be lacking in essential nutrients such as potassium and Vitamins B1, C, and K, so it is encouraging to find that fresh produce may possibly be grown and consumed safely to supplement astronauts’ diets.

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