Mediterranean-style dietary interventions in adults with cancer: a systematic review of the methodological approaches, feasibility, and preliminary efficacy

Cancer and its treatments can lead to excess body fat, decreases in lean mass, cardiotoxicity, and other side effects. The Mediterranean diet (MED-diet) has the potential to improve clinical and supportive care outcomes. The aim of this systematic review was to evaluate the feasibility, safety, and efficacy of the MED-diet on health outcomes in adults with cancer. Three databases were searched from inception to February 2023. Eligible studies included randomised controlled trials testing a MED-diet intervention among adults with cancer. Within- and between-group differences for adherence, dietary intake and health outcomes were extracted. Fifteen studies describing fourteen interventions were included, and there were considerable differences in study design and implementation of the MED-diet. Studies were predominately in women with a history of breast cancer. The MED-diet was safe with no adverse events reported, and feasible with high adherence and/or increases in MED-diet-compliant foods. The MED-diet when applied with an energy restriction below estimated requirements for weight loss demonstrated reductions in body weight (range: −3.9 kg to −0.7 kg). Interventions that showed significant reductions in body weight also improved quality of life. There is limited evidence to evaluating the MED-diet on cardiovascular and inflammatory markers, and heterogenous MED-diet prescriptions impede definitive conclusions on these health outcomes. The MED-diet was feasible and safe for adults with cancer. There were reported benefits for weight loss following a MED-diet when an energy restriction was applied, however further evaluation to determine the effects on cardiometabolic biomarkers and other outcomes are required.