October 2, 2019

The Antioxidant N-Acetyl-cysteine Improves Sperm Quality

Another potential treatment option in male infertility
Daily supplementation with N-acetyl-cysteine for 3 months in men with abnormal sperm improved sperm quality and reduced markers of oxidative stress, which may contribute to male infertility.


Jannatifar R, Parivar K, Roodbari NH, Nasr-Esfahani MH. Effects of N-acetyl-cysteine supplementation on sperm quality, chromatin integrity and level of oxidative stress in infertile men. Reprod Biol Endocrinol. 2019;17(24).

Study Objective

To determine the impact of supplementation with the antioxidant N-acetyl-cysteine (NAC) on sperm quality, chromatin integrity, and level of oxidative stress in infertile men with abnormal seminal parameters


Three-month prospective, randomized, blinded, clinical trial


Fifty men, aged 25 to 40 years, with asthenoteratozoospermia as determined by WHO criteria. Participants reported no prior impregnations and had female partners without fertility issues.

Subjects with conditions and/or risk factors known to impair fertility (hormonal abnormalities, Klinefelter’s syndrome, varicocele, cryptorchidism, vasectomy, leukospermia, sperm antibodies, anatomical disorders, cancer, abnormal liver function, cigarette smoking, alcohol consumption, fever within 90 days of semen analysis) were excluded.


All participants received 600 mg oral NAC supplementation daily for 3 months.

Study Parameters Assessed

Semen analysis was used to assess the following seminal parameters: volume, sperm concentration, total motility, progressive motility, non-progressive motility, immotile sperm, and abnormal morphology. Other recorded data included DNA fragmentation index, levels of protamine deficiency, total antioxidant capacity (TAC), seminal malondialdehyde (MDA) levels, and hormonal parameters including serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone, and prolactin. Assessments were performed at baseline and at 3 months.

Primary Outcome Measures

Findings at 3 months were compared to those at baseline.

Key Findings

After 3 months of NAC, significant improvements were noted in all the seminal parameters evaluated: volume (P=0.01), sperm concentration (P=0.02), total motility (P=0.01), progressive motility (P=0.001), non-progressive motility (P=0.01), immotile sperm (P=0.01), and abnormal morphology (P=0.001).

There were also significant reductions in the percentages of DNA fragmentation (P=0.001) and protamine-deficient sperm (P=0.009). Levels of oxidative stress improved from baseline, as shown by a decrease in MDA (P=0.01) and an increase in TAC (P=0.01). All hormonal parameters except prolactin showed statistically significant differences, with decreases in FSH (P=0.01) and LH (P=0.04) and an increase in testosterone (P=0.01).

Practice Implications

Male-factor infertility accounts for a significant percentage of infertility cases, with a prevalence approximately equivalent to that of female-factor infertility.1 Several etiologies have been identified, including congenital anomalies, genetic inheritance, poor lifestyle, environmental exposures, and iatrogenic conditions. If no cause is identifiable, a diagnosis of unexplained or idiopathic infertility is given.2 While the terms “unexplained” and “idiopathic” are often used synonymously, there is an important distinction. Patients with true unexplained infertility present with a normal workup, including semen analysis. In contrast, those with idiopathic infertility present with a normal workup, except for suboptimal semen analysis findings.3 The participants in this study were classified as the latter, since poor motility and morphology were detected (asthenoteratozoospermia).

After 3 months of NAC, significant improvements were noted in all of the seminal parameters evaluated.

Idiopathic male infertility is a current topic of interest among researchers, with specific focus on the association between oxidative stress and abnormal seminal parameters. Oxidative stress occurs when there is an excess of reactive oxygen species (ROS) with insufficient antioxidant stores.4 Under normal physiological conditions, spermatozoa produce small amounts of ROS, which are necessary for prefertilization events (sperm hyperactivation, capacitation, acrosome reaction).5 When present in excess, ROS impair spermatogenesis and threaten overall sperm quality.6 Male idiopathic infertility commonly presents with aberrations in both ROS and antioxidants, suggesting that these individuals bear a greater burden of oxidative stress.4,7

In the present study, malondialdehyde (MDA) and total antioxidant capacity (TAC) served as biomarkers of oxidative stress. MDA is produced when ROS initiate lipid peroxidation of polyunsaturated fatty acids (PUFAs). Because plasma membranes of spermatozoa contain PUFAs, seminal MDA levels serve as an indicator of lipid peroxidation.8 Several studies have demonstrated higher levels of MDA in infertile males, compared to those who are fertile.9,10 These findings suggest that seminal lipid peroxidation and subsequent oxidative stress contribute to the seminal abnormalities associated with idiopathic male infertility.

While the mechanism by which oxidative stress alters normal sperm physiology is unknown, recent research has revealed that it affects DNA integrity. The DNA fragmentation index and protamine content are considered to be promising markers of DNA damage. They appear to predict fertility outcomes better than a semen analysis.11 In 2019, Borges et al demonstrated statistically significant correlations between a high level of sperm DNA fragmentation and poor embryo development, a low implantation rate, and a high miscarriage rate.12 Participants in that study were initially considered to have unexplained infertility. However, sperm abnormalities, in the form of DNA fragmentation, were detected in nearly 10%. These findings suggest that DNA fragmentation is a valuable marker of sperm abnormalities for some men and could be used in combination with a semen analysis to strengthen the diagnostic work-up for male infertility.13

The association between oxidative stress, DNA damage, and poor sperm quality appears to be well-documented. Less clear is whether oxidative stress causes the DNA damage associated with seminal abnormalities. The present study demonstrated notable improvements in oxidative stress, DNA integrity, and sperm quality with antioxidant supplementation in the form of NAC. Other studies on antioxidant therapy for male infertility have reported similar results. However, rigorous studies revealing clear clinical outcomes are limited, and most of the research concludes that further investigation is warranted.14 In the meantime, it appears reasonable to target oxidative stress, whether through antioxidant supplementation or otherwise, in the treatment of male idiopathic infertility. Current options for providers are extensive, with a growing list of antioxidant supplements including selenium, L-carnitine, acetyl-l-carnitine, coenzyme Q10, zinc, folic acid, myo-inositol, vitamin E, vitamin C, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and now NAC.15-20

Categorized Under


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