Beneficial Effects of Antioxidants in Male Infertility Management: A Narrative Review

Abstract

Background: Infertility, defined as the failure to conceive after one year of regular, unprotected intercourse, affects 50–80 million people worldwide. A male factor is involved in approximately 20–30% of cases. In the etiology of male infertility, the association between poor semen quality and oxidative stress (OS) is well known. High levels of reactive oxygen species (ROS) allow the oxidation of DNA, proteins, and lipids of sperm cells, modifying their vitality, motility, and morphology. Methods: To evaluate the effects of antioxidants on sperm in infertile men, we queried the MEDLINE database (via the PubMed interface) for published studies in the last 10 years (2011–2021). The following keywords were used: “infertility” and -“inositol”, -“alpha-lipoic acid”, -“zinc”, -“folate”, -“coenzyme Q10”, -“selenium”, and -“vitamin”. Results: Inositol regulates OS levels in sperm cells thanks to its role in mitochondrial reactions and is involved in several processes favoring sperm–oocyte interactions. Alpha-lipoic acid (ALA) reduces ROS damage and improves semen parameters in terms of spermatozoa’s motility, morphology, and count. Poor zinc nutrition may be related to low quality of sperm. Supplementation of folate plus zinc has a positive effect on the sperm concentration and morphology. Supplementation with CoQ10 increases sperm concentration, total and progressive motility. Selenium (Se) supplementation improves the overall semen quality and is related to a higher ejaculated volume. Among vitamins, only vitamin B12 shows a positive effect on semen quality; it increases sperm count and motility and reduces sperm DNA damage. Conclusions: In men showing low-quality semen, diet supplementation with antioxidants may improve the sperm quality by alleviating OS-induced sperm damage and enhancing hormone synthesis and spermatozoa concentration, motility, and morphology. Future clinical trials should be focused on the possible association of several antioxidants to take advantage of combined mechanisms of action.