And that brings manned missions to Mars one step closer.

For some time, leading space agencies and companies have fantasized about manned missions to Mars. NASA plans to undertake its first human mission to the red planet around 2030. And if it’s up to SpaceX, it’ll get there sooner. However, there is a lot to consider if we actually want to travel to this distant planet. Not least because our bodies are not really made for such a trip to Mars. For example, our bones lose considerable mass. But a bowl of ‘wonder lettuce’ could offer a solution.

bone loss

With current technology, it would take about 10 months to reach the red planet with a manned vessel. Add to that the return journey and a year-long stay on Mars and you soon find yourself on a three-year mission, during which astronauts are exposed to the microgravity of space for extended periods of time. Meanwhile, thanks to manned missions to the ISS, we know that such a space journey does not really improve your bones. In fact; Due to the lack of gravity, bones slowly but surely lose mass, increasing the risk of bone fractures.

That’s right

Previous studies have shown that astronauts on long space missions lose on average more than 1 percent of their bone mass per month. Why is that so? “Normally, the bones in our bodies are constantly being broken down and reshaped,” researcher Kevin Yates told from. “Calcium plays an important role in the production of bone tissue. However, the balance of these processes is shifted in microgravity. The bottom line result is a loss of bone mass. The shift likely occurs because bones are no longer subject to gravity.”

bone fractures

Scientists have been looking for solutions for some time now; how can the strength in bones be maintained during long space travel? “It’s very important to prevent bone fractures,” Yates said. “In space and on Mars, this will be debilitating and difficult to treat.” At present, astronauts on the ISS follow strict training regimes in an attempt to maintain bone mass. But they usually don’t stay on the ISS for more than six months. A return trip to Mars takes much more time. And that means future Mars travelers are much more vulnerable to bone disorders, such as osteoporosis. “So we’re going to have to treat bone loss with drugs,” Yates said. “Exercise alone is not enough to prevent bone loss.”


Fortunately, there is already a cure. A drug containing a peptide fragment of human parathyroid hormone (PTH-Fc; a hormone produced by the body) stimulates bone formation and can help restore bone mass under microgravity. There is, however, a major drawback. And that is that this drug requires daily injections. However, it is very impractical to have to carry large amounts of medicines and syringes in the suitcase to Mars. And so Yates, along with his colleagues, wanted to find a way for astronauts to produce it themselves during their deep space travels.


And they succeeded, they write in a new study. Astronauts on the ISS have already shown that they can grow ordinary lettuce in this limited environment. And so the researchers wanted to develop a transgenic lettuce that expresses the PTH peptide in a form that can be taken orally. Successfully. “We have modified bacteria (Agrobacterium tumefaciens) used to stop a gene encoding PTH-Fc in plant cells,” explains Yates when asked. “We grew whole plants from those cells that were transformed by the bacteria. Those plants in turn produced seeds from which we could grow offspring. We then screened the transgenic lettuce plants and their progeny for PTH-Fc production.”

This lettuce produces a bone-stimulating hormone that can help prevent bone loss in space. Image: Kevin Yates

380 grams per day

The preliminary results show that the plants express an average of about 10 to 12 milligrams of the modified peptide hormone per kilogram of fresh lettuce. According to Yates, this means that future Mars travelers will need to eat about 380 grams of lettuce a day to get enough of the hormone, which can be called a ‘fairly large salad’. The researchers are now also trying to screen all these transgenic lettuce lines in order to fish out the specimens with the highest PTH-Fc expression. Because the higher the expression, the smaller the amount of lettuce that needs to be consumed.

First step

They are promising results. With the study, the researchers have therefore taken the first essential step towards a lettuce that produces a bone-stimulating hormone. And one day, astronauts could even grow this lettuce in space. All they have to do is transgenic lettuce seeds – which are very small; a few thousand fit in a thumb-sized vial – to put in their suitcase. They can then be grown in space in the same way as regular lettuce. According to the researchers, this way astronauts kill two birds with one stone; not only does eating the special lettuce help them maintain strong bones, they can also enjoy tasty vegetables; a welcome relief from the mainly canned and freeze-dried food that astronauts are still served.


Although the researchers haven’t tasted the lettuce yet because its safety has not yet been established, they expect it—like most other transgenic plants—to taste just like its regular counterpart. “I can say that our transgenic lettuce at least looks and smells like normal lettuce,” says Yates.

Before the transgenic lettuce can grace the plates of astronauts, the researchers first plan to optimize the PTH-Fc expression levels. Then they will test the lettuce for its ability to safely prevent bone loss in animal models and human clinical trials. The team also wants to test how well the transgenic lettuce grows in the ISS and whether it produces the same amount of PTH-Fc there as on Earth. All in all, there is still a long way to go. But promising, those are the findings for sure. “I think it could provide a solution to a problem that needs to be solved before humans can successfully undertake long-term reconnaissance missions,” Yates said. And so the transgenic lettuce may play an important role in future manned distant space missions.