Infertility, which affects similar to 15% of the world's population, is a global public health issue recognized by the WHO. Therefore, it is of major clinical and public health importance to investigate whether modifiable lifestyle factors-such as stress, drug use, smoking, alcohol intake, and diet-may influence human fertility. A systematic review and meta-analysis of randomized clinical trials (RCTs) from the MEDLINE-PubMed database was conducted to assess the effect of nutrients, dietary supplements, or food on sperm quality parameters. In total, 28 articles were included for qualitative analysis and 15 for quantitativemeta-analysis. Total spermconcentrations [expressed asmean differences (MDs); 95% CIs, in spermatozoa (spz)/mL] were increased by selenium (3.91 x 10(6) spz/mL; 3.08, 4.73 spz/mL), zinc (1.48 x 10(6) spz/mL; 0.69, 2.27 spz/mL), omega-3 (n-3) fatty acids (10.98 x 10(6) spz/mL; 10.25, 11.72 spz/mL), and coenzyme Q10 (CoQ10) (5.93 x 10(6) spz/mL; 5.36, 6.51 spz/mL). Spermcounts were increased by omega-3 fatty acids (18.70 x 10(6) spz/mL; 16.89, 20.51 spz/mL) and CoQ10 supplementation (10.15 x 10(6) spz/mL; 8.34, 11.97 spz/mL). Sperm total motility was increased by selenium (3.30%; 2.95%, 3.65%), zinc (7.03%; 6.03%, 8.03%), omega-3 fatty acids (7.55%; 7.09%, 8.01%), CoQ10 (5.30%; 4.98%, 5.62%), and carnitines (7.84%; 6.54%, 9.13%), whereas sperm progressive motility was increased only after supplementation with carnitines (7.45%; 6.24%, 8.67%). Finally, sperm morphology was enhanced by selenium (1.87%; 1.50%, 2.24%), omega-3 fatty acid (0.91%; 0.69%, 1.13%), CoQ10 (1.06%; 0.72%, 1.41%), and carnitine (4.91%; 3.68%, 6.15%) supplementation. This meta-analysis of RCTs suggests that some dietary supplements could beneficially modulate sperm quality parameters and affect male fertility. However, results must be cautiously interpreted due to the limited sample size of the meta-analyzed studies and the considerable observed interstudy heterogeneity.