Endometriosis is a gynecological condition in which tissue that resembles the tissue that lines the uterus grows outside of the uterus.

The condition can cause endometrial tissue to grow on pelvic organs, including the ovaries, fallopian tubes, and bladder, and even other organs in the abdominal cavity, such as the bowel and appendix.

It is a complex, chronic, estrogen-dependent, inflammatory syndrome that affects more than 190 million people worldwide.

Endometriosis is characterized by symptoms like constipation, chronic lower abdominal and pelvic pain, painful menstruation and sexual intercourse, bloody stools, and infertility.

There’s no cure for endometriosis, and treatment focuses on improving symptoms. Current treatments include hormonal therapy, surgery, or a mix of both.

However, hormonal therapy can lead to side effects, including hot flashes, bone loss, and an increased risk of breast cancer — in addition to high costs.

And surgical interventions can come with risks of infection and complications. Plus, surgery doesn’t guarantee permanent relief from endometriosis, with recurrence rates as high as 67%.

Recently, research on N-acetyl cysteine (NAC) has uncovered its potential as a prospective treatment for endometriosis. Some studies suggest that it is a highly effective, low cost medicine with virtually no adverse effects.

This article reviews NAC and whether it helps with endometriosis symptoms.

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N-acetyl cysteine (NAC) is a nutritional supplement that comes from the amino acid L-cysteine. According to research, it is safe and inexpensive and has been commercially available since at least the 1960s.

NAC is a powerful antioxidant with strong free radical-scavenging activity.

Antioxidants are compounds that help mitigate oxidative stress, an imbalance caused by an excess of free radicals in your body that leads to inflammation and cell damage and is involved in the development of multiple chronic diseases.

Aside from being an antioxidant, NAC promotes detoxification and serves as a precursor for glutathione (meaning that it stimulates its production), which is one of the most important naturally occurring antioxidants.

For this reason, NAC has been considered as a potential treatment option for diseases characterized by chronic inflammation, such as endometriosis.

Dosage and safety

N-acetyl cysteine (NAC) is available to purchase over-the-counter as a dietary supplement.

The typical dose is 600–1,200 mg per day, but consider talking with a healthcare professional before using NAC to be sure that you’re taking a safe dose and that no medicines you take interact negatively with it.

For most people, side effects are uncommon and usually very mild.

NAC hasn’t been well-studied in children age 12 and under, so check in with a provider before giving NAC to a child in your care.

Medical therapy for endometriosis centers on improving quality of life through pain control, prevention of disease recurrence, preserving fertility, and delaying or avoiding the need for surgery.

As mentioned before, current treatments for endometriosis include:

  • Hormonal therapy: focused on managing endometriosis-related pelvic pain by suppressing estrogen production, which inhibits ovulation, menstruation, and reduces inflammation.
  • Surgery: aimed at removing out-of-place endometrial tissue, also known as cysts or lesions.
  • In vitro fertilization: used to help people conceive if their fertility has been affected.

Nevertheless, both current and older research suggests that NAC has the potential to be a non-hormonal alternative to typical treatments for endometriosis, with the advantages of preserving fertility and causing virtually no negative side effects.

Here’s how NAC may help with endometriosis symptoms, according to research:

NAC may reduce inflammation, a cause of endometriosis pain

Older and recent research suggests that endometriotic cells have been associated with increased production of reactive oxygen species (ROS), which are pro-inflammatory compounds that cause the disease’s chronic inflammation.

For this reason, it is believed that antioxidant compounds like NAC could be used as safe and efficient treatments for endometriosis.

Laboratory and human studies show that as an antioxidant, NAC may offer anti-inflammatory effects by scavenging ROS and decreasing the activity of pro-inflammatory markers.

Furthermore, older studies found that by reducing inflammation, NAC seems to lead to a reduction in pelvic, menstrual, and sexual pain — the first targets of endometriosis treatment.

It may reduce high estrogen levels, which are associated with endometriosis

Estrogen is a sex hormone produced mainly by the ovaries. Because endometriosis is an estrogen-dependent disorder characterized by abnormally high levels of this hormone, the purpose of hormonal therapy is to reduce its production.

Evidence shows that NAC seems to help treat endometriosis by blocking a chain of reactions that leads to estrogen production, which starts by blocking an inflammatory enzyme called cyclooxygenase-2 (COX-2).

According to a 2013 study, a decrease in COX-2 levels lowers the production of prostaglandin E2 — the most powerful stimulator of aromatase.

Since aromatase is an enzyme needed for estrogen synthesis, by blocking the activity of COX-2, NAC indirectly leads to estrogen reduction.

It may decrease cyst size and growth

Once more, some older and recent evidence suggests that NAC may help treat ovarian endometriosis by reducing cyst size.

Older laboratory studies show that NAC’s antioxidant properties may help decrease the abnormally rapid growth of endometrial cells, reducing both cell invasiveness and cyst size.

A 2013 study including 92 people with endometriosis administered 600 mg of NAC 3 times per day for 3 consecutive days per week, while another group did not take NAC.

After 3 months, 24 of the 47 people in the NAC-treated group canceled scheduled surgical procedures meant to alleviate their endometriosis — 14 of them due to decreased cyst size and 4 due to disappeared cysts.

In the group that did not take NAC, only 1 person canceled their surgery.

The study concluded that NAC treatment led to a higher number of cysts shrinking or disappearing, which reduces pain. In addition, it also led to a smaller number of enlarged and newly formed cysts.

Nevertheless, despite the promising results, human studies evaluating the effectiveness of NAC in endometriosis are still limited. Thus, further research is needed.

Living with endometriosis

Endometriosis can be a difficult diagnosis to receive. And since chronic pain and other symptoms associated with the disease can affect your quality of life and emotional outlook, it’s important to have a strong support group around you.

Consider reaching out to the following organizations to find support groups near you or to connect with online communities.

People with endometriosis could benefit from the following recommendations:

  • Ask about oral contraceptives. Contraceptive pills help reduce estrogen production by slowing or reducing your periods. Evidence also suggests that they may be effective in reducing the frequency of the disease, with the advantage that they can be consumed for a long time.
  • Ask about GnRH antagonists. Gonadotropin-releasing hormone (GnRH) agonists have long been used to treat endometriosis because they reduce estrogen levels. However, low doses of GnRH antagonists may offer a faster way to achieve the same effect while maintaining low estradiol levels, which helps reduce unwanted side effects.
  • Ask about aromatase inhibitors. Inhibiting the enzyme aromatase eliminates all estrogen production. Aromatase inhibitors seem to successfully treat pelvic pain and significantly reduce cyst size.
  • Ask about anti-angiogenic therapy. The growth of newly formed blood vessels — known as angiogenesis — seems to be a key factor for cyst growth. Thus, its inhibition (or anti-angiogenesis) may offer a new non-hormonal therapy for the treatment of endometriosis. However, human research is still in its early stages.
  • Eat foods rich in cysteine and anti-inflammatory compounds. While NAC is not found in natural food sources, cysteine — the amino acid from which it’s derived — is present in chicken, turkey, eggs, garlic, yogurt, wheat germ, broccoli, and Brussels sprouts. Also, eating anti-inflammatory foods, such as those rich in omega-3 fatty acids and resveratrol, may lower your risk of disease,
  • Avoid pro-inflammatory foods. Consider avoiding high intakes of alcohol, red meat, and trans fats, which are considered risk factors that may increase the risk of endometriosis due to increasing inflammation in the body.

Learn more about ways to manage endometriosis pain here.

Here are some questions people often ask about NAC and endometriosis.

How does NAC affect your hormones?

Evidence suggests that NAC may help regulate levels of the sex hormone estrogen by inhibiting a series of enzymes — namely COX-2, prostaglandin E2, and aromatase — which results in estrogen reduction.

Further research shows it may also affect progesterone, estradiol, testosterone, and insulin production.

Does NAC get rid of inflammation?

As a powerful antioxidant itself that also stimulates the production of the antioxidant glutathione, NAC helps fight oxidative stress and, thus, may reduce inflammation.

Can NAC cause menstrual bleeding?

Research into polycystic ovary syndrome (PCOS) shows that NAC may positively affect menstrual regulation in ways comparable to metformin — a drug commonly used to treat PCOS.

NAC is a low cost nutritional supplement that shows promising beneficial effects for treating endometriosis.

According to research, it may be a potential non-hormonal alternative to current hormonal treatments due to its reductive effect on inflammation, estrogen levels, and cyst size and growth.

In addition, it seems to have virtually no adverse effects. Yet, human research is still in its early stages, and further studies are needed to validate it.