Inflammatory leukocytes are a major source of oxidative stress in semen.  These cells release enzymes, such as myeloperoxidase, which can generate reactive oxidants that could adversely affect sperm fertility.  We carried out a pilot study, measuring sperm fertility parameters in young adult males, on three occasions over a three month period. We correlated these with the level of myeloperoxidase in semen.  Since vitamin C is a potent scavenger of reactive oxygen species, and has other potential anti-inflammatory activities, participants consumed 200 mg/d vitamin C following baseline measurements.

Semen parameters (volume, concentration, total count, viability and morphology) were evaluated using WHO guidelines, sperm motility was assessed by computer-aided sperm analysis (CASA) and sperm DNA damage was gauged using the sperm chromatin structure assay (SCSA).  Seminal vitamin C was measured by high-performance liquid chromatography (HPLC) and myeloperoxidase protein levels and activity were determined in whole semen, cell pellet and seminal plasma using enzyme-linked immunosorbent assay (ELISA). 

Eight of the 13 participants had high levels of myeloperoxidase in their seminal plasma (15-250 ng/ml). This is up to 10-fold higher than levels typically found in blood plasma. Strong correlations were observed between high levels of myeloperoxidase in seminal plasma and decreased sperm counts (r = -0.69, P < 0.001), as well as a decreased percentage of rapidly motile sperm (r = -0.44, P = 0.021) over the duration of the study.  No effect of vitamin C supplementation was observed on any of the parameters measured.  A larger study is planned to confirm the observed correlations between seminal myeloperoxidase and decreased sperm fertility parameters.