Did you know that the diet of Tenebrio molitor influences not only its size, but also its nutritional value and its ability to fight off disease? A recent scientific study has shown that the balance between proteins, carbohydrates, and fats in its diet is key to obtaining a high-quality, sustainable, and healthy product. We’ll tell you about the results and why they are important for the future of T. molitor protein.
We’re hearing more about mealworms as the food of the future. And it’s no wonder: they’re a source of high-quality protein, require less water and land than traditional livestock, and can be raised on organic waste. But, like any living thing, they need proper nutrition to grow well and reach their full potential.
They’re rich in protein (up to 60% of their dry weight), healthy fats, vitamins, and minerals. Furthermore, the European Union has already authorized them as a “novel food” for human consumption. But there’s an important detail: what they eat directly determines what they later offer us.
Traditionally, they’re raised on wheat bran, but this ingredient is expensive and is also used for human food. Therefore, scientists are looking for more economical and sustainable alternatives, such as bakery byproducts (cookies, dough scraps) or agricultural byproducts (rice hulls, coffee grounds). The challenge is finding the perfect mix that allows them to grow quickly, accumulate plenty of nutrients, and, moreover, remain healthy and strong.
A team of researchers from the University of Turin (Italy) has set out to unravel this mystery. In a study published in the journal Animal, they tested four different diets based on these byproducts and measured how they affected the growth, nutritional composition, and, for the first time, the ability of T. molitor to produce its own natural defences against microbes. The results are fascinating and have practical applications for anyone interested in raising mealworms.
Proteins, carbohydrates and fats: the magic trio
Imagine mealworms as tiny athletes. To perform well, they need a balance of:
- Protein: These are the building blocks for muscle and tissue. Protein is the nutrient we value most because it’s from protein that we obtain mealworm powder for animal and human consumption.
- Carbohydrates: These are the fuel. They provide the energy needed to move, grow, and develop into adults.
- Fats (lipids): These are also energy, but more concentrated, and are essential for forming cell membranes and producing hormones.
The study compared two protein-to-carbohydrate ratios: one with more carbohydrates (1:3) and another with more protein (1:2). They also tested two levels of dietary fat: low (7.5%) and high (9.5%). This resulted in four different menus, all made with low-cost ingredients such as bakery scraps, rice hulls, and coffee grounds.
What happened to growth?
Researchers fed thousands of individuals for several weeks and weighed them every seven days. They observed that:
- Initially (first 5-7 weeks): those consuming less fat (7.5%) grew faster, especially if their diet was high in carbohydrates.
- Later (from week 8 onward): diets with a higher protein ratio (1:2) took the lead. Those consuming more protein ended up weighing more at the end of the experiment.
Furthermore, those on the high-carbohydrate diets reached their maximum size earlier (week 9), while those on the higher-protein diets continued growing for an additional week (week 10). This suggests that carbohydrates accelerate development, but protein prolongs the fattening period, which may result in larger individuals.
And regarding nutritional quality…
It’s not just the size that matters, but what’s inside. Chemical analyses revealed notable differences:
- More protein: Those fed 1:2 diets (more protein) had a slightly higher protein content (almost 38% compared to 37%). But the most interesting finding is that combining a 1:3 diet with low fat resulted in the highest protein content of all (39%).
- More fat: Those with the highest fat content were the ones fed the high-carbohydrate, high-fat diet, reaching almost 40% fat by dry weight. This is because excess carbohydrates are converted into fat for energy storage.
- Less chitin: Chitin is the material that forms the exoskeleton. In some food applications, low chitin levels are desirable because it can be indigestible. The higher-protein (1:2) diets resulted in individuals with less chitin, which is good news for digestibility.
Natural defences: when diet strengthens the immune system
The most novel aspect of the study is its analysis of how diet affects the ability of T. molitor to produce antimicrobial peptides. These peptides are essentially the natural “antibiotics” they manufacture to protect themselves from bacteria and fungi. The researchers measured the activity of two of these peptides: Cecropin-2 and Coleoptericin-1.
The diet combining a 1:2 protein-to-carbohydrate ratio and a high fat content increased Cecropin-2 production almost ninefold compared to the 1:3 protein-to-carbohydrate diet with low fat. Coleoptericin-1 production also increased, though to a lesser extent. In other words, a balanced diet not only makes the birds fatter but also more resistant to potential diseases.
This is highly relevant for breeding facilities because birds with stronger immune systems will require fewer external treatments and will be more robust against pests and infections. Furthermore, these antimicrobial peptides could have applications in animal feed or even in medicine, further enhancing their value.
Water saving and efficiency
The study also measured water consumption using an agar gel (a type of gelatine used as a hydrating agent). Those consuming higher-protein diets (1:2) drank less agar, indicating they were making better use of the moisture in their food. This translates into resource savings and greater production efficiency.
Final thoughts
What conclusions can we draw from all this? The main one is that diet matters, a lot. There’s no single recipe that achieves everything, because each production goal requires a different balance:
- If we want large, high-protein individuals, the best approach is a 1:2 ratio (more protein) and a moderate fat level (7.5%).
- If we’re looking for individuals with a strong natural defence (more antimicrobial peptides), the winning combination is the same 1:2 ratio, but with more fat (9.5%).
- If sustainability and low cost are our priorities, all the diets were formulated with byproducts, demonstrating that good results can be achieved without resorting to premium ingredients.
These findings are great news for the Tenebrio protein sector. At Protiberia, we’re committed to a farming model based on the circular economy, using agri-food waste to obtain high-quality protein. This type of research helps us better advise our protifarmers and design more efficient and sustainable fattening processes.
Science is advancing to show that insects are not only the food of the future, but that we can raise them intelligently, in an environmentally friendly way, and adapted to the needs of each moment.
At Protiberia, we actively support research and development initiatives to promote healthy insect colonies, advance insect farming, and create synergies with other livestock production systems, positioning insects as a sustainable alternative for both food and feed.
References
Daluwatta, S. S. K., Loiotine, Z., Bellezza Oddon, S., Candian, V., Biasato, I., Tedeschi, R., & Gasco, L. (2026). Dietary carbohydrates, protein and lipid modulation shapes growth, nutritional profile and antimicrobial peptides gene expression in edible yellow mealworm larvae. animal, 101915. https://doi.org/10.1016/j.animal.2026.101915
Kröncke, N., & Benning, R. (2022). Self-Selection of Feeding Substrates by Tenebrio molitor Larvae of Different Ages to Determine Optimal Macronutrient Intake and the Influence on Larval Growth and Protein Content. Insects, 13(7), Article 7. https://doi.org/10.3390/insects13070657
Montalbán, A., Sánchez, C. J., Hernández, F., Schiavone, A., Madrid, J., & Martínez-Miró, S. (2022). Effects of Agro-Industrial Byproduct-Based Diets on the Growth Performance, Digestibility, Nutritional and Microbiota Composition of Mealworm (Tenebrio molitor L.). Insects, 13(4), 323. https://doi.org/10.3390/insects13040323
