Let’s Talk: NAC

NAC, or N-acetyl cysteine, is a powerful supplement that greatly affects inflammation, endometriosis, PCOS, fertility, pregnancy and other areas of health. So what is it, and what does the research say?

What is NAC?

N-acetyl cysteine, or NAC, is an antioxidant that can be used as a supplement. It is a precursor of L-cysteine that results in glutathione, one of the most powerful antioxidants in the body. Antioxidants are essential for reducing oxidative stress or free radicals in the body and reducing inflammation, deterioration and other factors preventing the body from working as efficiently as possible. 

Due to its antioxidant behaviour, NAC can be a potential treatment option for different disorders resulting from free oxygen radicals. It also assists in the clearance of mucus as it has properties as a biofilm disruptor. It has been used for treating and managing various diseases and conditions as a direct action or in combination with other medications.

Sources of NAC

NAC can be found in small quantities in foods such as meat, fish, seafood, chicken, turkey, eggs, whole-grain products such as bread and cereals, and some plant foods, including broccoli, onions, and legumes.

From a medicinal perspective, we rarely find enough NAC in nature to meet the quantities required to have a therapeutic effect. Therefore, it can be necessary to supplement with NAC under the guidance of a practitioner. 

What does the research say?


A study released in March 2023 looked at the effectiveness of NAC in reducing endometriosis-related pain, the size of ovarian endometriomas and improving fertility in those with endometriosis. 120 patients aged between 18–45 years old were prescribed NAC for three months. After the study, there was a significant reduction in the size of ovarian endometriomas, endometriosis-related pain and levels of inflammation. 

75% of patients who wanted to become pregnant achieved spontaneous pregnancy within six months of beginning NAC therapy which is significant when looking at a population with endometriosis. An additional 10% of patients who didn’t achieve spontaneous pregnancy achieved pregnancies after assisted reproduction therapies.

Another study from 2013 found such a reduction in endometriosis-related pain that a third of participants in the NAC treatment group cancelled upcoming laparoscopies. This study concluded that NAC is a simple yet effective treatment for endometriosis, without side effects, and is a suitable approach for women desiring pregnancy.

Male infertility

Males who experience subfertility often have higher levels of semen reactive oxygen species (ROS) than fertile men. High levels of semen ROS can cause sperm dysfunction, sperm DNA damage and reduced male reproductive potential, all impacting conception outcomes. After taking NAC for three months, significant increases in patients’ sperm count and motility were seen. In contrast, abnormal morphology, DNA fragmentation and protamine deficiency showed significant decreases compared to pre-treatment levels.


Various trials have examined NAC and its impact on assisted reproductive technologies, including IVF. Controlled ovarian hyperstimulation is a critical step in fertility treatment for many people. Unfortunately, repeated controlled ovarian hyperstimulation leads to oxidative stress in follicle fluid and ovarian granulosa cells, which decreases the egg quality and reduces the likelihood of conception. While an animal study was done, and we’re awaiting more research, the results suggest that NAC increases mitochondrial function in eggs and improves egg quality.

A study from 2022 looked at the impact of NAC on IVF outcomes for women over 35. This found the number of higher-quality blastocysts was greater among patients receiving IVF cycles along with NAC treatment than those directly undergoing IVF cycles, which can increase the chances of a successful pregnancy. 


NAC has been proven to be very effective at inducing ovulation in people who experience PCOS. The research has found women who use NAC have a higher likelihood of ovulation, getting pregnant, and maintaining that pregnancy when compared to a placebo. A more recent meta-analysis found NAC supplementation decreased total testosterone levels and increased FSH levels in people with PCOS and that NAC supplementation might be effective in improving reproductive function in people with PCOS.

There are a few studies where NAC has been compared to, or used alongside, different medications. When compared to clomiphene citrate alone, those who used NAC and clomiphene citrate were more likely to ovulate (52.1% versus 17.9%), and the average E2 and progesterone levels and the endometrial thickness were significantly improved. In another study, NAC was compared to metformin which found NAC had better improvement in clinical, biochemical and hormonal profiles than Metformin in PCOS patients. Due to its effectiveness and limited adverse effects, it was recommended NAC be used as a substitute for insulin-reducing medications, like Metformin, in treating PCOS patients.

Miscarriage prevention

Recently, there has been an increase in research into the impact of oxidative stress on pregnancy, and the findings have been that an increase in oxidative stress increases the risk of miscarriage. As NAC is a powerful antioxidant, there has also been interest in the impact of NAC to reduce oxidative stress and improve pregnancy outcomes. 

When looking at a group of 166 women with a history of recurrent, unexplained pregnancy loss who were treated with NAC and folic acid or folic acid alone, NAC alongside folic acid caused a significantly increased in the pregnancy continuation rate up to and beyond 20 weeks gestation.

Addiction and behaviour change

NAC can also be beneficial when addressing addictions and changing behaviours. This includes reducing alcohol consumption and quitting smoking which is important for fertility and during pregnancy.  Research indicates NAC may be effective at reducing consumption of alcohol by approximately 30% as it assists in reducing cravings. It has also been proven to have similar results when considering quitting smoking. Reducing alcohol consumption and quitting smoking have significant health benefits, particularly regarding fertility and pregnancy.

If you’re interested in taking any supplements, please discuss this with your practitioner to ensure you’re taking the correct dose and form for you. This article is not intended to be medical advice and is purely for education purposes.