Ultra-processed diet proves deadly for cockroaches in lab study

A laboratory experiment with 127 cockroaches has revealed something counterintuitive about one of nature's most resilient creatures: feed them only what humans eat from a bag or box, and they die at twice the rate of their cousins eating apples and potatoes.

Researchers at an unnamed institution maintained a breeding colony of lobster cockroaches—Nauphoeta cinerea, a species native to northeastern tropical Africa but now common across North and South America—and divided them into three groups over two months. One group received only ultra-processed foods: Sour Punch Straws and Lay's potato chips, both classified as ultra-processed under the NOVA food classification system. A second group ate unprocessed foods, the colony's standard diet of apples and potatoes. The third group received a mix of both. Each diet group contained roughly 40 to 43 individuals housed in three separate containers, with equal numbers of males and females, kept at 18 degrees Celsius with controlled humidity.

The results were stark. Cockroaches fed exclusively ultra-processed food experienced a 47 percent mortality rate over the two-month period. Those on unprocessed diets died at a 20 percent rate. The mixed-diet group fell between them at 23 percent—a figure statistically indistinguishable from the unprocessed group. The difference between ultra-processed and unprocessed was significant enough that the researchers could rule out chance as an explanation.

This finding matters because cockroaches are urban animals. They thrive in human cities precisely because they can eat what we discard. Yet the experiment suggests that access to only processed foods—the kind that dominate grocery shelves in wealthy countries, where ultra-processed items now account for more than half of all calories consumed—carries a real cost. In humans, such diets are linked to cancer, hypertension, diabetes, depression, and obesity. The mechanisms remain debated: whether it is the poor nutritional profile, the addictive palatability that drives overconsumption, the displacement of healthier foods, or some combination of these factors. Animal studies in mammals and birds have documented similar harms—malnutrition, impaired growth, oxidative stress, fatty liver disease, disrupted gut bacteria, elevated cholesterol. But evidence from invertebrates has been scarce until now.

The study cannot explain why the ultra-processed diet proved deadly. Food was provided in excess and replenished weekly, but researchers did not measure how much each cockroach actually ate or compare the nutritional content of the diets. They cannot say whether the problem was the processing itself, specific ingredients like additives or high levels of salt and sugar, the overall nutritional imbalance, or simply that cockroaches ate less of food they found less appealing. The fact that the mixed diet showed no mortality penalty is suggestive—it hints that access to unprocessed food, whether by preference or availability, may protect against the worst effects. But the study design cannot confirm this.

What the experiment does establish is that an exclusively ultra-processed diet reduced survival in this cockroach species, consistent with what researchers have observed in vertebrates. The finding raises a question that extends beyond insects: as human food systems expand into cities and wild spaces, what happens to the animals that depend on our scraps? Do urban-adapted species develop preferences for processed foods? What are the ecological consequences if they do? The cockroach, long celebrated as a survivor, has met something it cannot simply endure. Whether that matters to the species' long-term success in cities—where, after all, both processed and unprocessed foods remain available—remains an open question.