Abstract
Environmental pollution, sedentary lifestyles, and unhealthy dietary patterns have been hypothesized as the main modifiable factors of human semen quality decline. The study aimed to assess the associations between an a priori-defined Mediterranean diet (MedDiet) adherence and semen quality parameters or medically assisted reproductive (MAR) outcomes in males. A systematic review was conducted with studies from PubMed, Embase, or Scopus databases until October 2024. A priori-defined MedDiet adherence was considered as exposure and conventional semen quality parameters as the primary outcomes. Secondary outcomes included MAR outcomes, reproductive hormone concentrations, and sperm DNA fragmentation. A quality assessment was performed using the NHLBI tool. Meta-analysis was conducted following Cochrane guidelines. A subgroup analysis was done for healthy participants and those from fertility clinics separately. A sensitivity analysis was performed to check the influential studies. A qualitative analysis was performed on 11 eligible articles (n = 2558 individuals). Data from 9 observational studies showed a positive association between the adherence to MedDiet and semen volume (1/9), sperm concentration (5/9 studies), count (5/9), total motility (5/9), progressive motility (4/9), vitality (1/9), normal morphology (2/9), or follicular stimulating hormone (1/9). Among these, the links between MedDiet adherence and MAR outcomes were prospectively explored only in 1 study, which reported no association. A total of 8 studies were eligible for meta-analysis (n = 1835 individuals). Total MedDiet adherence showed a significant positive association with sperm count (24.37 M spz.; 1.30-47.44; I(2) = 89%), total motility (8.81%; 2.26-15.37; I(2) = 88%), progressive motility (7.49%; 1.47-13.50; I(2) = 86%), and normal morphology (1.02%; 0.21-1.82; I(2) = 77%). Evidence from 2 randomized clinical trial evaluating the effect of MedDiet on semen parameters aligns with the primary results. Evidence from observational studies and clinical trials shows potential benefit of adhering to a MedDiet in terms of seminal quality parameters, but not fertility outcomes. This study was registered at PROSPERO as CRD42024584003.