Association Between Dietary Polyphenol Intake and Semen Quality: Insights from the FERTINUTS Study

Background/Objectives: Low semen quality and male infertility are critical global health issues. Emerging research highlights that nutritional factors could play a significant role in determining reproductive outcomes. Understanding and optimizing these dietary influences, including the role of polyphenols, is crucial for developing targeted strategies to improve male fertility. We aimed to explore the relationship between the intake of different classes of polyphenols and semen quality indicators in a cohort of healthy young males. Methods: This is a secondary analysis involving 106 male individuals, aged 18–35 years, from the FERTINUTS trial. Dietary intake was assessed using 3-day dietary records, and semen quality parameters were analyzed. Multivariable linear regression analysis was employed to evaluate the associations between dietary polyphenol consumption and semen quality indicators. Results: Our findings revealed both positive and negative associations between polyphenol consumption and sperm morphology parameters. A higher intake of total polyphenols was associated with a lower percentage of abnormalities in sperm heads but a higher rate of abnormalities in the principal piece. Similar results were observed for lignan and flavonoid intake. Additionally, a higher intake of flavonoids was also associated with a greater percentage of normal sperm forms. In contrast, a higher dietary intake of stilbenes was associated with a higher percentage of combined abnormalities. Conclusions: Higher intake of polyphenols, particularly flavonoids and lignans, was associated with improved sperm head morphology but also with increased tail abnormalities, although no associations with motility or vitality were observed. These results suggest that specific polyphenol classes may have both beneficial and adverse effects on sperm structure, warranting consideration of compound type and dosage in dietary recommendations. Further studies are needed to determine whether these morphological changes impact fertilization outcomes and reproductive potential.