By Chris D. Meletis, N.D.
What is N-acetyl cysteine and how can it support both male and female fertility? N-acetyl cysteine—NAC, for short—is an amino acid that boosts levels of a powerful antioxidant known as glutathione.
NAC is a popular dietary supplement with a variety of health benefits. These include loosening mucous in your nasal passages and supporting lung health.1 It can also keep your immune system healthy.2
But perhaps one of the most interesting benefits of NAC is its ability to support fertility, in both men and women.
NAC for Male Fertility
Research has shown that NAC can support male fertility by reducing the oxidative stress that damages sperm. The sperm of men that are experiencing fertility issues have higher levels of reactive oxygen species (ROS) compared with sperm from men with optimal fertility. These high levels of ROS in semen can lead to dysfunctional sperm, DNA damage in the sperm, and reproductive problems.3
A number of studies investigated NAC’s role in male fertility. Research found that:
- Giving NAC to infertile men leads to increased sperm count and improved sperm motility.3
- NAC improves abnormal sperm structure and DNA damage to the sperm,3 4 and it increases testosterone levels, too.3
- NAC boosts the total antioxidant capacity and causes a drop in oxidative stress.3,4
NAC also teams up with other antioxidants to give a significant boost to semen concentration and sperm motility in men with an unexplained reduction in semen quality (a condition known as idiopathic male infertility).5
A formula containing NAC and other antioxidants also improves sperm shape and structure and reduced DNA damage and oxidative stress in idiopathic infertile men.
In men with unexplained male infertility (infertility of unknown origin with normal sperm) the NAC/antioxidant formula didn’t have as strong as an effect compared to in men with idiopathic infertility. Even so, it still improved sperm motility and DNA damage, as well as reduced oxidative stress.
A review of various studies found that combinations of antioxidants including NAC also improved live birth rates, along with other fertility-related benefits.6
NAC for Female Fertility
NAC may also be a girl’s best friend when it comes to female fertility. According to a number of studies, NAC can:
- Protect ovarian follicles in human ovarian tissue7
- Induce ovulation in women with polycystic ovary syndrome when used together with clomiphene citrate (a fertility drug).8
- Improve the take home baby rate in a group of women with a history of unexplained recurrent pregnancy loss, when combined with folic acid.9
- Reduce the risk of preterm births in women with bacterial vaginosis.10
- Support healthy blood pressure during pregnancy when combined with other antioxidant supplements in women who had low levels of antioxidants.11
One particularly interesting study—although it was in animals—investigated the effects of NAC on mouse oocytes exposed to the toxin known as bisphenol-A (BPA).12 NAC protected the oocytes from BPA-caused damage.
If this also holds true in humans, it’s a significant finding as BPA is a common toxin found in some food can linings, plastic water bottles, and cash register receipts.
The reason why NAC is so beneficial? Much of its fertility-enhancing effects are due to its ability to reduce oxidative stress.
We should point out that even though there are a lot of studies showing NAC is beneficial, it didn’t help in every instance. In one study of women undergoing a type of treatment known as intracytoplasmic sperm injection, which is used together with in vitro fertilization, NAC did not significantly increase the probability of pregnancy.13
NAC Health Benefits After Birth
Necrotizing enterocolitis is a gastrointestinal disorder that primarily impacts preterm babies. Preterm infants with necrotizing enterocolitis have an elevated risk of brain injury and neurodevelopmental dysfunction.14
Rodent research shows that necrotizing enterocolitis can cause inflammation in the brain of newborn animals.14 However, giving rodent mothers NAC in the last three days of pregnancy before giving birth or intravenous administration of NAC to newborn rodent pups, led to reduced brain inflammation in rat offspring.14
Scientists will need to conduct studies in human babies to confirm whether NAC can play a beneficial role in necrotizing enterocolitis.
The Bottom Line on NAC and Fertility
There’s a lot of good research to show NAC likely plays a role in supporting both male and female fertility. It’s beneficial for sperm health, ovulation, and maintaining a healthy pregnancy—to name a few benefits. It is important to understand, however, that most of the research done to date has looked at the benefits of NAC in men and women with suboptimal fertility – less is known about the benefits of oral supplementation with NAC in healthy men and women with optimal fertility.
NAC is sold as a standalone dietary supplement and also combined with other antioxidants. Always consult with your healthcare practitioner before beginning a supplement regimen.
About Dr. Meletis
Dr. Meletis is an internationally recognized naturopathic physician, an accomplished author, and respected educator in the field of natural medicine. Dr. Meletis was honored as a ‘Naturopathic Physician of the Year’ by the American Association of Naturopathic Physicians for his commitment to education and helping those in need. His mission is simply, “changing the world’s health, one person at a time”.
He has authored 14 books on subjects ranging from natural medicine interactions to fertility enhancement and has published over 80 articles in publications such as Natural Health and Natural Pharmacy. Dr. Meletis has served as the Dean of Naturopathic Medicine and Chief Medical Officer for the National College of Naturopathic Medicine (NCNM) for seven years and later as the school’s Senior Science Officer. He sits on several medical advisory boards and has worked with Oregon Health and Science University on a grant from the National Institute of Health to further educate MD graduates on natural medicine.
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- De Flora S, Grassi C, Carati L. Attenuation of influenza-like symptomatology and improvement of cell-mediated immunity with long-term N-acetylcysteine treatment. Eur Respir J. 1997;10(7):1535-1541.
- 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(1):24.
- Barekat F, Tavalaee M, Deemeh MR, et al. A Preliminary Study: N-acetyl-L-cysteine Improves Semen Quality following Varicocelectomy. Int J Fertil Steril. 2016;10(1):120-126.
- Arafa M MA, Agarwal A, et al. Is there a role for oral antioxidants in the treatment of infertile men with high sperm DNA fragmentation? Paper presented at: Foundation of Reproductive Medicine Annual ConferenceNovember 2018; New York.
- Majzoub A, Agarwal A. Systematic review of antioxidant types and doses in male infertility: Benefits on semen parameters, advanced sperm function, assisted reproduction and live-birth rate. Arab J Urol. 2018;16(1):113-124.
- Olesen H, Pors SE, Jensen LB, et al. N-acetylcysteine protects ovarian follicles from ischemia-reperfusion injury in xenotransplanted human ovarian tissue. Hum Reprod. 2021;36(2):429-443.
- Badawy A, State O, Abdelgawad S. N-Acetyl cysteine and clomiphene citrate for induction of ovulation in polycystic ovary syndrome: a cross-over trial. Acta Obstet Gynecol Scand. 2007;86(2):218-222.
- Amin AF, Shaaban OM, Bediawy MA. N-acetyl cysteine for treatment of recurrent unexplained pregnancy loss. Reprod Biomed Online. 2008;17(5):722-726.
- Shahin AY, Hassanin IM, Ismail AM, Kruessel JS, Hirchenhain J. Effect of oral N-acetyl cysteine on recurrent preterm labor following treatment for bacterial vaginosis. Int J Gynaecol Obstet. 2009;104(1):44-48.
- Rumiris D, Purwosunu Y, Wibowo N, Farina A, Sekizawa A. Lower rate of preeclampsia after antioxidant supplementation in pregnant women with low antioxidant status. Hypertens Pregnancy. 2006;25(3):241-253.
- Li Q, Zhao Z. Influence of N-acetyl-L-cysteine against bisphenol a on the maturation of mouse oocytes and embryo development: in vitro study. BMC Pharmacol Toxicol. 2019;20(1):43.
- Elgindy EA, El-Huseiny AM, Mostafa MI, Gaballah AM, Ahmed TA. N-acetyl cysteine: could it be an effective adjuvant therapy in ICSI cycles? A preliminary study. Reprod Biomed Online. 2010;20(6):789-796.
- Zmora O, Gutzeit O, Segal L, et al. Maternal N-acetyl-cysteine prevents neonatal brain injury associated with necrotizing enterocolitis in a rat model. Acta Obstet Gynecol Scand. 2021;100(5):979-987.