Positioning earthworms in the future foods debate: a systematic review of earthworm nutritional composition in comparison to edible insects
Sustainable food system innovations are urgently needed to feed a growing human population while staying within planetary boundaries. Farmed edible insects have received considerable scientific and public attention due to their potential to improve food system circularity by upcycling nutrients from organic residual streams to nutritious food. Earthworms, as non-insect invertebrates, have remained largely unrecognized in the future foods debate. However, they are already widely farmed at industrial scale for their capacity to recycle organic wastes and improve soil fertility. We conducted a systematic literature review to provide a quantitative basis on earthworm nutritional composition, thereby positioning earthworms in the future foods debate. Here we show, based on evidence from 142 scientific studies, that farmed earthworms are a potentially interesting food source. They have an attractive nutrient composition compared to the main farmed edible insect species, being especially rich in protein, low in fat and containing a favourable profile of essential amino acids. The content of important fatty acids, minerals and vitamins in earthworm biomass is higher or lower than in edible insects, depending on the feed material. Crude protein and fat contents are higher in farmed versus wild earthworms, indicating that farming conditions provide a lever for further improving the nutritional composition of earthworm biomass. Whether earthworm species or feed materials affect earthworm nutritional composition could not be finally clarified based on the available data. We conclude that earthworms have high potential as a future food from a nutritional perspective, mainly as an alternative source of protein. The integration of earthworm farming in future food systems can be expected to improve sustainability and circularity, potentially giving earthworms an advantage over edible insects.