MeDiBREAST Study Probes Mediterranean Diet's Impact on Breast Cancer Gut Microbiota

Dr. Cristina Royo, a specialist in internal medicine at Nostra Senyora de Meritxell Hospital, has launched the MeDiBREAST study to examine how a Mediterranean diet affects the gut microbiota of breast cancer patients and whether this influences treatment outcomes.

The research, led by the oncology service at Andorra's Servei Andorrà d'Atenció Sanitària (SAAS), aims to determine if a healthier microbiota reduces toxicity from oncological treatments, potentially improving patient responses. Royo explained that the diet emphasises vegetables, legumes, proteins and olive oil, with a focus on variety—drawing on evidence from trials like Predimed, which link it to lower cardiovascular risk and a diverse bacterial profile in the gut.

Unlike prior studies centred on chemotherapy responses, MeDiBREAST targets toxicity levels. "We want to see if the Mediterranean diet shapes the microbiota and, in turn, cuts side effects during treatment," Royo said.

The six-month trial involves 25 patients recently diagnosed with any type of breast cancer, at any stage, all treated at the hospital. A nutritionist will guide participants through a tailored diet. Adherence will be assessed via interviews, Mediterranean diet adherence scales, microbiota analysis and metabolomics testing—conducted with support from Barcelona's Hospital Clínic.

Funding includes a €8,477.85 donation from the Associació de Dones, raised through its women's race.

Royo stressed the value of locally generated evidence. "In research, it's crucial to produce our own data from our patients and healthcare system, yielding conclusions relevant to Andorra—not just imported from a US hospital," she said. The primary goal is for patients to report better quality of life.