Glyphosate is the active ingredient of Roundup^®, which is one of the most popular herbicides worldwide. Although many studies have focused on the reproductive toxicity of glyphosate or glyphosate-based herbicides, the majority of them have concluded that the effect of the specific herbicide is negligible, while only a few studies indicate the male reproductive toxicity of glyphosate alone. The aim of the present study was to investigate the effect of 0.36 mg/L glyphosate on sperm motility and sperm DNA fragmentation (SDF). Thirty healthy men volunteered to undergo semen analysis for the purpose of the study. Sperm motility was calculated according to WHO 2010 guidelines at collection time (zero time) and 1 h post-treatment with glyphosate. Sperm DNA fragmentation was evaluated with Halosperm^® G2 kit for both the control and glyphosate-treated sperm samples. Sperm progressive motility of glyphosate-treated samples was significantly reduced after 1 h post-treatment in comparison to the respective controls, in contrast to the SDF of glyphosate-treated samples, which was comparable to the respective controls. Conclusively, under these in vitro conditions, at high concentrations that greatly exceed environmental exposures, glyphosate exerts toxic effects on sperm progressive motility but not on sperm DNA integrity, meaning that the toxic effect is limited only to motility, at least in the first hour.

Background/Objectives: Male infertility is a growing public health concern, with lifestyle and dietary factors increasingly recognized as contributors to impaired sperm function. Oxidative stress plays a central role in sperm damage, yet the relationship between seminal antioxidant capacity, dietary antioxidant intake and semen quality remains unclear. This study investigated the association between seminal plasma antioxidant status, sperm quality parameters and dietary antioxidant intake, while accounting for key lifestyle factors. Methods: A total of 105 men (18–55 years) undergoing semen analysis were enrolled. Semen parameters were evaluated according to the WHO guidelines. Seminal plasma antioxidant capacity was assessed using the Ferric Reducing Antioxidant Power (FRAP) and DPPH radical scavenging assays. Dietary antioxidant intake was estimated using a validated food frequency questionnaire, and lifestyle factors (smoking, alcohol consumption, physical activity, supplement use) were recorded. Correlations and multivariable regression models were applied to examine associations between antioxidant indices and semen quality. Results: Seminal antioxidant capacity showed wide inter-individual variability (FRAP: 1.6–2171.4 μmol Trolox eq/L; DPPH: 28.5–3093.2 μmol Trolox eq/L). Dietary antioxidant intake demonstrated very weak correlations with semen parameters (r < 0.20). Regression analyses identified smoking and higher body weight as strong negative predictors of sperm concentration, total count and motility, whereas physical activity was positively associated with morphology and progressive motility. FRAP exhibited a mixed association with motility subtypes, while supplement use was positively associated with vitality. Conclusions: Lifestyle factors—particularly smoking, body weight and physical activity—were stronger determinants of semen quality than dietary antioxidant intake or seminal antioxidant indices. These findings highlight the importance of modifiable behaviors in male reproductive health and suggest that improving lifestyle habits may offer greater benefits than dietary antioxidant intake alone.