Ionizing Radiation-Induced Microbiota Dysbiosis

Abstract

Ionizing radiation, whether environmental, diagnostic, or therapeutic, profoundly alters the gut microbiota, a key regulator of metabolism, nutrient absorption, and immunity. Radiation exposure disrupts microbial diversity, reduces beneficial taxa, and favors opportunistic species, impairing functions such as short-chain fatty acid production, vitamin synthesis, and bile acid metabolism. These disturbances weaken intestinal integrity and trigger systemic inflammation. In radiotherapy, especially for abdominal or pelvic cancers, dysbiosis is linked to gastrointestinal toxicity, inflammation, and reduced treatment tolerance. Radiation-induced microbial changes also affect gut–brain communication, influencing cognitive and emotional functions. Drawing from animal and human studies, this chapter explores how radiation reshapes microbial ecosystems and impacts host physiology. Understanding these mechanisms is vital for predicting radiation responses and developing microbiota-based strategies to protect intestinal and systemic health.