HMN 2026: How Gut microbiome thrives on fiber—tapeworms confirm it

Intestinal worms can help reduce inflammation in the human body—but only if they have enough dietary fiber. Without it, they switch into a hibernation-like state and their protective effect disappears. This is the finding of a new study by parasitologists from the Biology Center of the Czech Academy of Sciences, published in the journal Nature Communications.

Intestinal parasites were a common part of the human digestive system for most of our evolutionary history. In industrialized countries, however, they have largely disappeared over recent decades, typically attributed to improved hygiene and modern medicine. At the same time, the incidence of autoimmune and inflammatory bowel diseases has been rising. About two decades ago, this led scientists to explore the idea of using certain intestinal worms as a therapeutic tool—a concept known as helminth therapy.

“However, the results of helminth therapy have been inconsistent—sometimes the worms suppress inflammation, sometimes they do not. That’s why we focused on factors that may influence their effects in the gut,” says Kate?ina Jirk? from the Institute of Parasitology, Biology Center CAS. The researchers found that diet plays a crucial role, particularly the amount of dietary fiber.

The team investigated how an intestinal parasite behaves under different levels of dietary fiber in the host’s diet. As a model organism, they used the rat tapeworm Hymenolepis diminuta, which is commonly used in research on interactions between parasites, gut microorganisms, and the immune system. The species is non-pathogenic and has been shown to have anti-inflammatory effects.

“We found that when the diet contains a high proportion of structural fiber, the tapeworm is not only in excellent condition but is also able to induce an anti-inflammatory response in the host. When fiber is lacking, the worm enters an energy-saving state resembling hibernation in mammals, and its anti-inflammatory effect disappears,” explains Jirk?.

Under a low-fiber diet, the tapeworms remained several times smaller, failed to reach sexual maturity, and did not produce eggs. Genetic analyses further revealed extensive changes in gene expression related to development, metabolism, and reproduction.

Diet reshapes the entire gut ecosystem

Dietary changes also had a strong impact on the host’s gut microbiome. A fiber-rich diet promoted bacteria associated with a healthy gut environment, while a Western-style diet reduced microbial diversity and resulted in an expansion of bacteria linked to dysbiosis. These differences were also reflected in the host’s immune response.

According to the researchers, the findings highlight the fundamental role of diet in shaping the entire gut ecosystem. Health organizations recommend that adults consume around 25 to 30 grams of fiber per day, yet actual intake in Western countries is often lower. By contrast, traditional populations are estimated to consume as much as 80–120 grams of fiber daily.

A lack of dietary fiber depletes the gut microbiome, which numerous studies have shown to influence not only digestive health but also the immune system, brain function, and mental health. Microbial imbalance has been linked to an increased risk of allergies, depression, anxiety, and neurodegenerative diseases, including Alzheimer’s disease.

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