Nature: Ultra-Processed Foods Drive Evolution of Gut Bacteria

Human gut bacteria can evolve within just a few decades in response to dietary changes, according to evolutionary biologists from the University of California, Los Angeles. They found that in industrialized countries, certain microbes rapidly acquired genes that help digest starches from ultra-processed foods. The study was published in Nature.

The focus is on industrially derived starch compounds that began widespread use in the food industry only in the latter half of the 20th century. The authors note that such rapid genetic changes indicate strong natural selection pressures.

The researchers analyzed the genomes of nearly 30 gut bacterial species using data from different regions worldwide. They identified so-called “genetic sweeps”—DNA regions that became dominant within a species in a short time. A key mechanism behind these changes was horizontal gene transfer, a process in which bacteria exchange DNA with each other rather than only passing it to offspring.

Horizontal gene transfer is well known for rapidly spreading antibiotic resistance, but its role in the evolution of gut microbes had been poorly understood.

“The ability to digest new types of starch became a target of natural selection. Even more importantly, we see different evolutionary trajectories in gut bacteria of people from industrialized versus non-industrialized regions,” said co-author Richard Wolff, a graduate student.

A notable example is a gene associated with maltodextrin metabolism—a substance derived from corn starch and widely used in processed foods since the 1960s. This gene spread actively only among bacteria from people living in industrialized countries.

The researchers caution that it is not yet clear whether microbes are adapting specifically to maltodextrin or to a broader class of modified starches. Nevertheless, the contrast between traditional diets based on root vegetables and fruits and modern diets rich in snacks and processed foods clearly creates a new direction in microbial evolution.

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