Western diets seem to be responsible for the development of metabolic diseases, atherosclerosis, neurodegeneration, and cancer. All these pathologies are characterized by an inflammatory status, on one hand, and on the other hand, by an alteration of the gut microbiota. Synbiotics are a combination of prebiotics and probiotics endowed with the ability to reduce inflammation and keep equilibrium in the microbiota components. In human trials, synbiotics have successfully been administered in different pathologies, including aging. The elderly exhibit multiple deficits of innate and adaptive immunity and also have an altered microbiota which polarizes the immune response toward inflammation. Microbiota-induced modification of the immune response in the elderly may prevent or attenuate winter infections. However, clinical trials with synbiotics are still incomplete because assessment of the microbiota composition and monitoring of the peripheral immune response should proceed in parallel to identify the best synbiotic combination