Food as medicine offers a promising strategy for disease intervention. Preferences for drinking water at different temperatures may influence disease occurrence, development and treatment outcomes including cancer therapy. Radiotherapy-induced gastrointestinal (GI) syndrome narrows the therapeutic window and degrades the life quality of patients. In this study, we demonstrated that drinking warm water mitigated radiation-induced GI injury in mouse models. 16S rRNA gene sequencing showed that warm water preserved the gut microbiota and enriched symbiotic Lactobacillus johnsonii, which could alleviate intestinal radiation toxicity alone and generate synergistic radioprotective effect when combined with warm water consumption. Warm water elevated rectal temperature in irradiated mice, and exposure to higher ambient temperature accelerated the proliferation of L. johnsonii. Untargeted metabolomics and prokaryotic transcriptome sequencing analyses validated the alterations in physiological function of L. johnsonii under higher ambient temperature, particularly augmenting the purine biosynthesis. Blockage of purine production attenuated the radioprotective property of L. johnsonii. Together, our findings highlight the beneficial effect of warm water on radiotherapy-induced GI syndrome, underscore the gut symbiotic L. johnsonii as a candidate probiotic for use in food manufacturing to combat intestinal radiation injury.

The human microflora is a complex ecosystem composed of diverse microorganisms mainly distributed in the epidermal and mucosal habitats of the entire body, including the mouth, lung, intestines, skin, and vagina. These microbial communities are involved in many essential functions, such as metabolism, immunity, host nutrition, and diseases. Recent studies have focused on the microbiota associated with cancers, particularly the oral and intestinal microbiota. Radiotherapy, the most effective cytotoxic modality available for solid tumors, contributes to the treatment of cancer patients. Mounting evidence supports that the microbiota plays pivotal roles in the efficacy and prognosis of tumor radiotherapy. Here, we review current research on the microbiota and cancer development, and describe knowledge gaps in the study of radiotherapy and the microbiota. Better understanding of the effects of the microbiome in tumorigenesis and radiotherapy will shed light on future novel prevention and treatment strategies based on modulating the microbiome in cancer patients.