Three researchers have been eating worms for 105 days, while living in a sealed laboratory in Beijing, to test whether astronauts could use them as their main source of protein.

The volunteers fattened up the worms on plants grown inside the Moon Palace One biosphere at the Beijing University of Aeronautics and Astronautics, the South China Morning Post reports . They had various preparations for eating the worms - using a bean sauce and other seasonings to make the dish as appealing as possible.

The idea of feeding protein-rich mealworms to astronauts was apparently raised as early as 2009, but scientists at western space agencies worried they would be unappetising and lower astronaut morale. But researcher Hu Dawei says that throughout the current experiment the volunteers seemed "healthy and happy" on their worm diet. The UN's Food and Agriculture Organization has said edible insects could make a "promising alternative" to traditional protein sources.

"It did take them some time to adapt," Hu adds. "None of them had ever tried them as food before. Worms may look disgusting at first glance, but they are actually the cleanest and healthiest food source." But one restaurant owner is more sceptical, saying: "Worms on the menu might put off some people who dreamed of being an astronaut."