Biofortification for space farming: Maximising nutrients using lettuce as a model plant

Space exploration requires consideration of the dietary requirements of astronauts. Not only do nutritional requirements differ in space versus Earth, but limitations to payload combined with the length of space missions means that astronauts will need to produce as much food as possible in situ. Lettuce (Lactuca sativa) possesses many traits that make it suitable for space farming. Its small size, quick life cycle, large harvestable fraction and previous successful cultivation aboard the International Space Station (ISS) means that it represents a model plant for space cultivation. Here we discuss the suitability and requirements of lettuce as a dietary source on space missions. Using simplex linear programming, we identify the ration sizes of existing lettuce varieties to optimise nutrient delivery to both men and women on Earth and in Space. Whilst, unsurprisingly, a diet consisting only of lettuce cannot provide full nutrient requirements, there are differences in ration size and composition depending upon gender and location, indicating the importance of group composition when designing farming systems. We then review different routes to the biofortification of lettuce based on current literature and perform the modelling approach to determine portion sizes of theoretical ‘maximally fortified lettuce’, whose nutritional content was predicted based on the combined biofortification strategies. Finally, we conclude with the application of these approaches towards future space farming of a variety of crop species.