Background: Studies have shown that the amount of protein in the diet affects the hypothalamic-pituitary-testis axis and sub-optimal quantity reduces male fertility potential in both animals and humans. However, individual research reports on the factors associated with male infertility are collectively uncharacterized. Aim: We systematically reviewed, and meta-analysed animal (rats) studies on the effect of low protein diet on factors associated with male infertility. Methods: PubMed Central, EMBASE and Scopus databases were searched from inception to 30 March 2019 for the study concepts and related keywords in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Data on the outcome measures were extracted and pooled across trials using random-effects model and expressed as mean differences (MD) at a 95% confidence interval (CI). Results: Twelve trials identified from 3327 studies, met our inclusion criteria in the comparison of a low protein diet (2–10% protein) vs control protein diet (17–23% protein). The results showed that a low protein diet caused a significant reduction in the body weight ( P = 0.0001) testis weight ( P = 0.0001), seminal vesicle weight ( P = 0.0003), epididymis weight P = 0.02), serum testosterone ( P = 0.001) and follicle-stimulating hormone (FSH) concentrations ( P = 0.04) compared with the control treatments. No effect on luteinizing hormone (LH) plasma concentration ( P = 0.13) was observed. Conclusion: This study revealed that low protein diet caused significant reductions in body weight, testis, epididymis and seminal vesicle weights, serum testosterone and FSH concentration in rats. We infer that sub-optimal protein consumption reduces the gonadal and endocrine function, and consequently male infertility.
Research indicates that some adult diseases including reproductive pathologies are programmed in utero during foetal development. In particular, maternal low dietary protein, during the most critical developmental periods of male foetal development, may have a detrimental impact on male fertility through direct and epigenetic mechanisms. The aim of our study was to evaluate the impact of a gestational low protein diet on fertility markers in male offspring in rats through a systematic review and meta‐analysis. A systematic search using PubMed, and EMBASE databases was performed and two investigators independently screened the 1,703 prospective articles. Eleven articles met the eligibility criteria. Outcome measures were pooled using random‐effects models and expressed as mean differences (MDs) at 95% CIs for each study. The results reveal significant reduction in testis weight (MD (mean difference) −0.08 g; −0.12, −0.42; p = .0001), epididymal sperm count (MD −35.34 × 106 cells; −52.15, −18.53; p = .0001), number of Sertoli cells (MD −7.27 × 106 (−13.92, −0.62; p = .03), testosterone (T) concentration (MD −0.29 ng/ml; −0.48, −0.09; p = .004) and luteinising hormone (LH) concentration (MD of −0.24 ng/ml; −0.45, 0.04; p = .02) in comparison with controls. In contrast, follicle‐stimulating hormone (FSH) concentration (MD of 0.07 ng/ml; −0.16, 0.29; p = .56) was not significantly different from controls. We conclude that low gestational dietary protein maternal intake potentially negatively impacts fertility in male progeny later in life. The mechanisms of action responsible for these phenomena remain unclear.
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