Mealworms need more than plastic to be a nutritious food source

Mealworms need a minimum level of protein to grow and become a sustainable food source, according to a new study that challenges the myth that insects have superpowers of taking plastic waste and converting it to a nutritionally valuable product. 

Nutritional scientists from the University of Nottingham have tested diets comprising protein and all other nutrients against those containing little and none, and found that whilst mealworms could survive eating no protein they do need a minimum amount of protein to grow and pupate. Their findings have been published in the Journal of Insects as Food and Feed.

The larvae of the beetle Tenebrio molitor (yellow mealworms) were studied, the insect’s main components are protein, fat and fibre giving them high nutritional value, and the potential to be a sustainable alternative protein source, which is likely to be as animal feed but is also being explored as a possible sustainable food source for humans.

These mealworms have the versatility of being able to grow on relatively low quality food sources, such as wheat bran and other cereals as well as industry by-products such as distiller’s grains and garden and vegetable waste.

Recent research has also shown certain types of mealworm can be fed on polystyrene. This new research shows that this is not enough to produce the levels of growth and nutrition required to provide a food source and that the crude protein and fat composition of mealworms varies considerably, dependent on the feed utilised.

To prove that a minimum level of nutrition is required the teams fed groups of mealworms different diets containing varying amounts of nutritional components and protein. Mealworms fed the protein-free diets appeared to halt growth and didn’t enter the pupation stage of their life-cycle which is vital for breeding. This casts considerable doubt of the value of substrates free of protein (such as plastics) as viable feed sources for commercial production of mealworms.

John Brameld, Professor of Nutritional Chemistry at the University of Nottingham said: “Our research is focused on mealworms as an effective and sustainable alternative source of protein, and we are trying to find the optimum composition of nutrients to achieve this. This research is an important step towards that as we now know that despite what previous research has suggested, mealworms need all nutrients, including protein to be able to grow and pupate. Eating plastics alone or another non-protein diet does allow them to survive, but doesn’t provide the nutrients needed for the mealworms to be used as food.”

Tim Parr, Professor in Nutritional Biochemistry added: “Understanding the miniumum nutritional requirements for production animals such as mealworms is a vital part of being able to move towards using them at scale as a nutritious alternative food source. We now have that baseline and know that protein is a key requirement, so we can build on this with further work to fine tune the nutritional density and quantities of feed until we find a formula that is optimal for growth of the mealworm and delivery of key nutrients in a way that is is cost effective and sustainable.”