Mediterranean Diet, Semen Quality, and Medically Assisted Reproductive Outcomes in the Male Population: A Systematic Review and Meta-Analysis

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; I² = 89%), total motility (8.81%; 2.26-15.37; I² = 88%), progressive motility (7.49%; 1.47-13.50; I² = 86%), and normal morphology (1.02%; 0.21-1.82; I² = 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.

Keywords: Mediterranean diet; dietary pattern; fertility; male infertility; medically assisted reproduction; meta-analysis; sperm quality; systematic review; testicular function.

FIGURE 1

PRISMA flowchart of search and selection process. Exclusion criteria: non-human studies: animal studies or in vitro studies. population: age <18, females only cohort, azoospermic males, diseases such as cancer, among others. Exposure: Exposure is not Med Diet described using a priori indices. Outcome: does not have the outcomes of interest to the review (like semen parameters, fertilization outcomes, live birth, among others). Irretrievable: paper cannot be accessed. Type of article: reviews, opinion articles, case reports, letters, among others.

FIGURE 2

Forest superplot of pooled mean differences (MD) for studies showing the association between total MedDiet and semen quality parameters. CI confidence interval; MedDiet, Mediterranean diet; M spz., million spermatozoa; M spz., spermatozoa.