What happens when an urban-adapted insect is fed a diet built around chips and candy? A controlled experiment offers a revealing look at how human-made foods may affect species beyond our own.
Study: Ultra-processed food increases mortality in the cockroach Nauphoeta cinerea. Image Credit: Roberto Piras / Shutterstock
A recent study in the journal Scientific Reports evaluated whether ultra-processed food consumption affected mortality in the lobster cockroach, Nauphoeta cinerea.
Consumption and Health Impacts of Ultra-Processed Foods
Ultra-processed foods are designed to be highly profitable and often use low-cost ingredients, have a long shelf life, are convenient to consume, and are highly palatable.
Currently, ultra-processed foods account for more than half of caloric intake in high-income countries and up to a third in middle-income countries. These products can contain high levels of unhealthy fats, salt, and sugar while providing little or no vitamins, minerals, protein, and dietary fiber.
High consumption of ultra-processed foods is consistently associated with cancer, hypertension, diabetes, depression, and obesity. Whether these associations are causal remains debated, with hypotheses including poor nutritional composition, overconsumption linked to hyper-palatability, nutritional displacement, and confounding lifestyle factors.
Animal studies provide experimental evidence that ultra-processed food intake can lead to adverse health outcomes across species, including malnutrition, impaired growth, oxidative stress, fatty liver, disruptions in gut microbiome function, and higher cholesterol. While adverse effects have been reported in mammals and birds, the impact on invertebrates remains poorly understood.
Some urban invertebrates, such as pavement ants, consume processed foods, and honey bees can experience increased mortality after exposure to a toxin formed when high-fructose corn syrup is heated, but direct evidence on the effects of ultra-processed foods on invertebrate fitness is lacking.
Assessing the Effects of Ultra-Processed Diets on Lobster Cockroach Mortality
N. cinerea, commonly known as the speckled or lobster cockroach, is native to northeastern tropical Africa but is also widespread in North and South America and elsewhere in Africa. Lobster cockroaches mature in about three months, live one to two years, and females give birth to approximately 20 live young after a month of gestation, breeding throughout the year.
A breeding colony was maintained in the laboratory for 11 years, with periodic supplementation from outside sources to maintain genetic diversity. Cockroaches were housed in nine containers, three per diet group, each containing cardboard, bran substrate, and water, and kept at 18°C with 30–50% humidity. Each container held 10 to 20 individuals, with equal numbers of males and females, identified by abdominal morphology.
Cockroaches were assigned to three diets: ultra-processed (43 individuals), unprocessed (41 individuals), or mixed (43 individuals). The unprocessed diet, consisting of apples and potatoes, was the standard colony food. The ultra-processed diet included apple-flavored Sour Punch Straws and Lay’s potato chips, both classified as Group 4 (ultra-processed) in the NOVA system. The mixed diet included half unprocessed and half ultra-processed food. Each diet group had three replicates, for a total of 127 cockroaches across nine containers.
Food was provided in excess and replenished weekly, but food weight and individual consumption were not measured. Cockroaches remained on these diets for two months. Mortality was assessed by counting the number of live and dead individuals in each container. Mortality data were then analyzed using a generalized linear mixed model with a binomial error distribution, with diet as the explanatory variable.
Ultra-Processed Food Increases Mortality in Cockroaches
Cockroaches fed an ultra-processed diet had a significantly higher mortality rate of 47% compared to 20% for those fed unprocessed diets and 23% for those on mixed diets.
Overall, diet had a significant effect on mortality: ultra-processed food increased mortality compared to both unprocessed and mixed diets. No significant difference was observed between the unprocessed and mixed diets.
The experiment provides evidence that an exclusively ultra-processed diet reduced survival in this cockroach species, consistent with adverse effects reported in vertebrate studies.
The study cannot identify why the ultra-processed group had poorer survival. Because individual food intake was not measured and the study did not report nutritionally matched diets, it cannot determine whether processing, specific ingredients, diet composition, or differences in consumption drove the mortality pattern.
Conclusion
In this laboratory study, an exclusively ultra-processed diet significantly increased mortality in a common urban-adapted invertebrate pest. When cockroaches had access to both ultra-processed and unprocessed foods, mortality did not differ significantly from that in the unprocessed group, a pattern the authors suggest could be relevant to their success in cities. The current study findings raise questions about how human-derived foods affect nonhuman species in cities and whether access to different foods helps urban-adapted animals persist.
More research is needed to understand the mechanisms behind these effects, including the possible roles of food additives and gut health. The lack of increased mortality in the mixed diet group suggests that access to unprocessed food might mitigate some negative effects, or that cockroaches preferred the unprocessed option when both were available. Intake was not measured, so the study cannot distinguish between these explanations. Future research should also explore whether urban-adapted insects develop preferences for ultra-processed food and the broader ecological effects of human-derived diets on wildlife, especially in urbanizing environments.
