NAC for Thyroid Health – Dr. Izabella Wentz, Pharm D

A few years ago, I was asked: “If the supplement police came to your house and said you had to give up all but one of your supplements, which supplement would you keep, and why?”

My answer: N-Acetyl Cysteine (also known as NAC for short), because it has numerous benefits on multiple body systems!

Research has shown that NAC helps to reduce thyroid antibodies. It also supports our detoxification pathways (which are usually impaired in Hashimoto’s), as well as gut function.

Additionally, it can help asthma, osteoporosis, oxidative stress, chronic inflammation, and other concerns often seen in those with Hashimoto’s.

In this article, I’ll cover:

  • What NAC is
  • Why NAC is important for detoxification
  • How NAC supports people with Hashimoto’s
  • How NAC affects oxidative stress and chronic inflammation
  • How to incorporate NAC into your routine

What is NAC?

N-acetyl cysteine (NAC) is a sulfur-based derivative of the amino acid L-cysteine. In the body, it acts as a potent antioxidant, and has been noted to be nearly 100 percent hepatoprotective — in other words, it has the ability to prevent liver damage.

In the 1970s, NAC was found to be an antidote for Tylenol (acetaminophen) overdoses; and later, in the 1980s, it was discovered that NAC can help prevent toxic reactions to chemotherapeutic agents. [1]

The Role of NAC in Hashimoto’s and Liver Support

Those with Hashimoto’s often have an impaired ability to clear toxins and may have an overload or accumulation of toxins. [2]

Toxins can accumulate due to intestinal permeability, or “leaky gut,” which can result in the absorption of problematic substances and lead to impaired detox abilities. (Studies have shown that everyone with an autoimmune disorder, including Hashimoto’s, has some degree of intestinal permeability. [3])

Additionally, there are several other factors associated with Hashimoto’s that can cause an impairment in the ability of the liver to properly eliminate toxins from the body.

These include:

Because so many people with thyroid conditions are dealing with a toxic load on their bodies, I consider NAC to be a super supplement for people with Hashimoto’s. In the body, NAC turns into glutathione, an antioxidant that not only supports liver function, but also helps the liver to clear out heavy metals and other toxins. [4]

NAC supports healthy levels of glutathione by providing the body with cysteine, the rate-limiting factor (or factor that prevents the process from happening more quickly) of glutathione production. [5] By supporting healthy glutathione levels, NAC in turn supports optimal levels of TSH and thyroid antibodies (more on that later).

Additionally, experimental research and previous clinical studies have found that glutathione can help recover oxidative stress-induced liver damage in alcoholic and non-alcoholic liver diseases. [6] In one study where 30 middle-aged participants with non-alcoholic fatty liver steatosis were randomly selected to receive either vitamin C or NAC, researchers found NAC could improve liver function in patients with non-alcoholic fatty liver disease (NAFLD). [7]

For this reason, NAC can be highly beneficial when you consider starting your health journey with a liver support protocol. You can read more about the importance of liver support for Hashimoto’s in this article.

NAC for Oxidative Stress and Chronic Inflammation

While research shows other benefits, here I’ll focus on two fundamental conditions that supplementing with NAC can affect: oxidative stress and chronic inflammation. [8] These two conditions are monumental drivers in almost every disease imaginable, including Hashimoto’s.

One caveat – while I discuss them separately, many times they overlap. In other words, if you have chronic inflammation, you probably also have oxidative stress, and vice versa.

NAC and Oxidative Stress

Oxidative stress results when an imbalance occurs and our cells produce too many free radicals, knocking oxidants and antioxidants out of balance. [9] Many factors can trigger or exacerbate oxidative stress, including:

When oxidative stress occurs, the process can adversely impact the DNA, proteins, and lipids (fats) within our cells.

Researchers have found that free radicals can damage multiple cellular organelles and processes, disrupting normal physiology. While the body has several antioxidant defense mechanisms, too many free radicals can overwhelm our body and (among other things) impact gene expression, which could lead to inflammation.

Oxidative stress can also become a key driver in Hashimoto’s and other thyroid disorders. In fact, researchers have found increased levels of oxidative stress among people with Hashimoto’s. [10]

When our thyroid gland makes thyroid hormones, it simultaneously creates free radicals. [11] Without sufficient glutathione to keep that oxidative stress in check, excess amounts can impact other tissues.

Iodine Excess with Selenium Deficiency Process Chain Infographic

You can read more about this process in my article on iodine and Hashimoto’s.

As such, maintaining a minimal oxidative load is a fundamental piece in protecting thyroid cell function. NAC helps to reduce this oxidative stress by neutralizing the hydrogen peroxide (which can otherwise cause damage to the thyroid gland).

Studies have also correlated oxidative stress with various mood disorders common in people with Hashimoto’s, including depression and anxiety, because it causes nervous system impairment. [12] (Read more about depression and Hashimoto’s and anxiety and Hashimoto’s.)

NAC for Chronic Inflammation

Inflammation gets a bad rep, but in the right situation, it can benefit us. For example, if we cut our finger, the immune system rallies up its defenses and comes to the rescue. Swelling, redness, and other immediate signs often follow. This type of inflammation, called acute inflammation, works as a protective defense for the body, and then swiftly disappears when its job is done.

On the other hand, chronic inflammation is inflammation gone wild: while this low-grade inflammation quietly simmers and festers, all kinds of trouble can result.

The signs of chronic inflammation aren’t always obvious, but they can be harmful and even deadly. Studies connect chronic inflammation with many modern human diseases, including cardiovascular disease, type 2 diabetes, and cancer.

Chronic inflammation is a huge driver behind autoimmune diseases, like Hashimoto’s thyroiditis, as well. (As its name implies, anything ending with “itis” signals inflammation.)

In fact, researchers have found that several genes encoding different inflammatory cytokines can influence the severity of Hashimoto’s. [13]

NAC can help dial down that inflammation. In one study, researchers found this supplement provided anti-inflammatory benefits while increasing the enzymes superoxide dismutase (SOD) (which fights against reactive damaging oxidative molecules), glutathione, and glutathione S-transferase (GST). (These latter two enzymes also act against harmful oxidative molecules.) The researchers concluded that NAC has both anti-inflammatory and (bonus!) anti-ulcerative effects. [14]

NAC for Reducing Thyroid Antibodies

NAC is a precursor to the antioxidant glutathione. Glutathione is the most abundant antioxidant in your body, and is thus sometimes called the master antioxidant. It plays a role in many functions, including antioxidant defenses, nutrient metabolism, the regulation of cellular events (including gene expression and cell proliferation), and immune response.

Glutathione doubles as a heavyweight protector against oxidative stress that can also protect the body against chronic inflammation. [15] (Conversely, chronic inflammation can deplete glutathione levels.)

A depletion in glutathione levels has been implicated with higher levels of thyroid antibodies and may contribute to Hashimoto’s. One study conducted in 2012 found that Hashimoto’s patients had 62 percent lower levels of serum glutathione compared to age-matched controls. In this same study, a significant relationship was identified between serum glutathione levels, TPO antibodies, and TSH. The lower the glutathione, the higher the antibodies, and the higher the levels of TSH – suggesting hypothyroidism. [16]

As a precursor of glutathione, NAC can help to optimize glutathione levels and reduce thyroid antibodies.

NAC is an antioxidant in its own right. As a sulfur donor, it helps scavenge free radicals, and it does double duty, helping to boost glutathione levels by converting it into glutathione in the body. [17]

If you’re healthy, your body can make a solid supply of glutathione.

Unfortunately, many variables that overwhelm your body with oxidative stress and chronic inflammation, like stress, infections, and a poor diet, may result in your body making less than optimal amounts of this master antioxidant – which is not uncommon in those with Hashimoto’s.

NAC and Gut Health

Chronic inflammation underlies many gut conditions, including intestinal permeability, or leaky gut, which is one of the three factors that must be present in order for autoimmune diseases like Hashimoto’s to occur. Leaky gut involves damage to the body’s intestinal lining and causes tight junction malfunctions, which allow substances like bacteria and food particles that are not intended to go through your gut wall, to pass through.

Studies involving pigs have shown that NAC improves intestinal tissue damage, as is present with leaky gut, by creating signals that tighten the junctions (or “spaces”) within the intestinal wall. This, in turn, patches up the “leaks” in a leaky gut. [18]

When intestinal tissue damage is healed and leaky gut is reversed, many people may even be able to put their Hashimoto’s into remission!

NAC can also promote intestinal health by helping to detoxify intestinal bacteria and by breaking down biofilms. Biofilms are a collective of microorganisms that grow on biological surfaces and often house gut pathogens, which can, in turn, lead to infections. Today, many biofilms are becoming resistant to many clinical antibacterial treatments and host immune responses, so researchers are looking for new substances to combat these resistant biofilms.

A study in 2014 investigated NAC’s effectiveness in preventing the formation of biofilms, as well as in the destruction of existing ones. The study found that in combination with different antibiotics, NAC can significantly penetrate the deepest biofilm layers of bacteria that are becoming increasingly resistant to classical antibacterial treatments. [19]

This exciting discovery means that NAC can help us eradicate pathogens, which are commonly found in the gut and are often triggers of Hashimoto’s symptoms. (Read more about how pathogenic infections could be the root cause of your Hashimoto’s.)

NAC for Co-occurring Conditions

Incredibly well-researched studies support NAC’s efficacy for other conditions that often co-occur with Hashimoto’s. Let’s look more closely at some of the other benefits of NAC.

Respiratory Conditions

Those with autoimmune thyroid disease are more likely to develop, or already have, other autoimmune conditions, including asthma. [20] If you have a stubborn hacking cough and excessive mucus buildup due to asthma, NAC could help. This acetylated form of cysteine is also a mucolytic agent, which means it can break down and thin mucus, as its sulfur content can cleave the bonds in mucoproteins.

It may also benefit other respiratory-related conditions. [21] One meta-analysis of 12 randomized controlled trials, found that long-term (over six months) use of NAC reduced the risk of chronic obstructive pulmonary disease (which includes refractory asthma) becoming worse. [22]

Osteoporosis and Bone Health

Osteoporosis is more common in women with Hashimoto’s and thyroid conditions who take thyroid medications, as thyroid hormones speed up bone turnover. Researchers have found that inflammatory cytokines induce the expression of COX-2 (a chief driver of pain and inflammation among many chronic diseases) in the osteoblasts (cells responsible for the synthesis and mineralization of bones) of inflamed joints. This is followed by osteoclast activation, which breaks down bones. [23]

In one study, when NAC was added to rat bone marrow cultures, significant improvements were seen in the activity of alkaline phosphatase (levels of which increase when bones are growing) and osteoblastic cultures (cells that develop bone), as well as an upregulation of bone-related gene markers such as collagen. Another study found that NAC could inhibit the inflammatory process involved in bone resorption, by regulating COX-2 expression. [24]

Type 2 Diabetes

Inflammation (along with oxidative stress) plays a crucial role in the development of insulin resistance and type 2 diabetes. One study published in the medical journal Free Radical Research in 2018, compared a group of mice who were fed a high-fat diet for six months, with a group that was fed the same diet along with NAC. The group that was only fed a high-fat diet experienced a significant increase in body weight and body fat, a decrease in motor activity, and impaired glucose and insulin tolerance throughout the study. Meanwhile, the group that was fed NAC saw a significant increase in motor activity, improved glucose and insulin tolerance, as well as improvements to DNA, protein oxidative damage, and adipose (fat-storing) tissue inflammation. [25]

The results suggested that NAC can improve insulin resistance and chronic inflammation in obese mice, by providing anti-oxidative stress benefits.


Weight gain and metabolic disorders, including insulin resistance, often go hand-in-hand with thyroid conditions and inflammation. One 2016 study published in Pharmaceutical Research found that supplementing with NAC inhibited fat mass and obesity development in mice that were fed a high-fat diet. NAC also improved insulin resistance, suppressed fat from accumulating in the liver, and stimulated thermogenic (fat-burning) genes in the mice, suggesting that NAC may help protect against obesity and obesity-associated metabolic disorders. [26]

Supplementing with NAC

If you think NAC might be a good option for you, I recommend Rootcology’s Pure N-Acetyl Cysteine supplement.

If you are following the Liver Support Protocol as outlined in my Hashimoto’s Protocol book, I recommend that you continue taking NAC for three to six months after supporting your liver.

Rootcology NAC

It is also safe to take on an ongoing basis. Daily doses of 1,800 mg are usually recommended. I would generally take this supplement with food to avoid stomach upset. As individual needs may vary, I highly recommend working with a healthcare practitioner to determine optimal dosages for your condition.

Here’s what one person had to say about Rootcology Pure N-Acetyl Cysteine:

“I’ve been taking it nightly for over a month. My thyroid levels improved, especially my T4 to T3 conversion levels. I was able to cut my medication by half!”

For a limited time, I am offering a 10% off discount on Rootcology Pure N-Acetyl Cysteine. Simply enter the code NAC2023 at checkout to receive your discount through February 24th at 11:59pm PT.

If you are already utilizing NAC, or are considering giving it a try, I wanted to provide a quick heads-up about a recent regulatory situation regarding NAC.

After a warning letter from the FDA was issued in July 2020, there was a subsequent debate on whether or not NAC should be sold as a supplement, because it had previously been approved for use as a drug in 1963.

In 2021, Amazon made the decision to remove all products containing NAC from their site, likely as a precautionary measure. In response, the Natural Products Association (NPA) reached out to Amazon to let them know that the issue was not closed with the FDA, and that NAC is a product that has dual uses as both a drug and a supplement, like many other products on the market (such as niacin, fish oil, and potassium, which can be sold as over-the-counter supplements, or prescribed by a medical professional). [27]

After a thorough review, the FDA denied two petitions filed by the Council for Responsible Nutrition (CRN) and the Natural Products Association (NPA), asking them to not remove products with NAC from the definition of a dietary supplement. [28]

Despite these denied petitions, I am happy to report that at this time, NAC-containing supplements are once again available on Amazon.

Most recently, the FDA released guidance that they did not find safety concerns in their initial review, but that they have not yet reached a final decision relating to an alternative request to allow the use of NAC in dietary supplements.

If you find NAC helpful or are considering trying it, you can stock up now (my Pure N-Acetyl Cysteine is available through the Rootcology website) to ensure you have extra on hand, no matter what additional changes regarding its status as a supplement may be in store for it in the future.


While NAC is safe for most populations, it can interact with some medications. Do not take NAC if you are currently taking the following medications: ACE inhibitors, activated charcoal, antihypertensive drugs such as anticoagulant/antiplatelet drugs, blood thinners, nitroglycerin (a vasodilator), chloroquine, metoclopramide, and/or anticancer agents.

Even at high doses, researchers have found NAC to be safe and well-tolerated. However, it’s important to note that NAC can cause stomach upset, nausea, vomiting, and diarrhea if taken on an empty stomach, so it should be taken with food to lessen the likelihood of these reactions.

Additionally, I don’t recommend NAC for those with an expressed CBS mutation or a sulfur sensitivity (you can read more about that here), those who are prone to fainting, or those who have an active peptic ulcer.

Stop this supplement two weeks prior to surgery.

Consult with a physician prior to use if you have asthma, or if you are pregnant or breastfeeding. If you have any concerns about possible medication interactions, please speak with your functional medicine practitioner.

Please note that if you open a bottle of NAC supplements and notice a bad odor, you likely did not get a bad batch. NAC’s sulfurous compounds can often cause a “rotten-egg” smell — but that is normal! If you are concerned, however, I recommend contacting the supplement manufacturer.

The Takeaway

N-Acetyl Cysteine (NAC) is a multitasking supplement that can be especially beneficial for those with Hashimoto’s. I’ve created a graphic to sum up all the key benefits of NAC:

Benefits of Supplementing with NAC Infographic

If you have Hashimoto’s or any other autoimmune disease — or if you have chronic inflammation and oxidative stress — you may wish to consider taking this supplement.

If you haven’t picked up a copy of my book Hashimoto’s Protocol already, I encourage you to do so and begin with the Liver Support Protocol. All of the supplements I recommend to support your liver can be found in the Rootcology store, including N-Acetyl Cysteine.

I wish you well on your journey to health and healing!

If you’ve used NAC, what did you use it for, and did you notice any significant benefits? Have you ever used NAC or another precursor to boost glutathione levels?

I’d love to hear your story below!

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P.S. Be sure to sign up for my weekly newsletter to get a free book chapter, recipes, my Thyroid Diet Starter Guide, information about Rootcology supplements, and notifications about upcoming events and my latest research.


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Note: Originally published in December 2018, this article has been revised and updated for accuracy and thoroughness.