Astronauts Have Been Growing Lettuce in Space for Years. A New Study Says These Vegetables Could Make Them Sick

For years, astronauts aboard the International Space Station (ISS) have enjoyed fresh vegetables grown in microgravity—lettuce, peppers, radishes, even a few spicy chili peppers.

More recently, Chinese astronauts have followed suit, harvesting space-grown lettuce, cherry tomatoes, and chives aboard their own space station. But there’s a problem: These space salads might not be as safe as we thought.

A new study from the University of Delaware, funded by NASA, has revealed that vegetables grown in microgravity are more vulnerable to contamination from harmful bacteria like Salmonella.

On Earth, plants protect themselves by regulating their stomata—the tiny pores on their leaves and stems—closing them when they sense a threat. But in microgravity, plants seem to do the opposite, keeping their stomata open wider, making it easier for pathogens to invade.

To study this, researchers used a device called a clinostat, which continuously rotates plants to simulate weightlessness. Their experiments confirmed that Salmonella is more likely to infect leafy greens under these conditions.

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Even Beneficial Bacteria Stop Working

Scientists also tested whether Bacillus subtilis, a beneficial bacterium that helps plants fight pathogens on Earth, could protect space-grown lettuce. Unfortunately, in microgravity, it failed to provide the same defense. This suggests that space fundamentally alters the way plants interact with microbes, both good and bad.

These findings raise concerns about food safety aboard the ISS and highlight a major challenge for future space farming.

With Earth’s population growing and arable land shrinking, space agriculture is increasingly seen as a viable solution. For now, one thing is clear: Future space farmers will need to be careful about food safety. And a good old-fashioned hand wash with soap and water? Absolutely essential.

Image | NASA

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