Ingestion of monosodium glutamate (MSG) in adult male rats reduces sperm count, testosterone, and disrupts testicular histology

Objective: Monosodium glutamate (MSG) is a widely used food additive with controversial side effects. Though neonatal administration of MSG has been shown to affect fertility via arcuate nucleus ablation, the body of work involving the effects of adult MSG administration on male rat fertility has yet to be collectively assessed. Design: Systematic review. Methods: A PubMed search using terms “monosodium glutamate” in addition to “male fertility” or “male reproduction” or “sperm” or “testes” was performed. Inclusion criteria included: English language, adult administration of MSG, male reproductive outcomes, and control groups. Additional studies were identified via reference lists of relevant articles. Results: Of 167 records originally identified, six studies remained after removal of duplicates and studies not meeting inclusion criteria. Data ranges included: cohort sizes of 24 – 32 animals, dosing from 0 to 4 g/kg, MSG administration duration of 10 – 56 days, and weight 75 – 200g. In MSG fed rats compared to controls: Sperm count was lower in three of four studies, serum testosterone concentration was lower in two of two studies, testicular component weights or size was decreased in two of three studies, and abnormal testicular and sperm histology was observed in five of six studies. Conclusion: Adult intake of MSG can negatively impact sperm count and serum testosterone concentrations as well as testicular morphology and histology in rats. Further investigation of this effect should be evaluated in humans for such a popular flavor enhancer.