N-acetyl cysteine (NAC) is a supplement form of cysteine, a conditionally essential amino acid. NAC has many health benefits, including replenishing antioxidants and nourishing your brain.
NAC is considered ‘conditionally essential’ because your body can produce it from other amino acids. It becomes essential only when the dietary intake of methionine and serine is low.
Cysteine is found in most high protein foods, such as chicken, turkey, yogurt, cheese, eggs, sunflower seeds, and legumes.
Consuming adequate cysteine and NAC is important for various health reasons, including replenishing the most potent antioxidant in your body, glutathione. These amino acids also help with chronic respiratory conditions, fertility, and brain health.
Here are the top 9 health benefits of NAC.
NAC is valued primarily for its role in antioxidant production. Along with two other amino acids — glutamine and glycine — NAC is necessary to make and replenish glutathione.
Glutathione is one of your body’s most important antioxidants — compounds that help neutralize free radicals that can damage cells and tissues. Antioxidants help support the body’s natural immune system and toxin-elimination processes. Research also suggests that antioxidant intake can reduce the risk of several chronic conditions, including cardiovascular disease. (
NAC helps replenish glutathione, arguably your body’s most powerful antioxidant. Therefore, it may help improve a variety of health conditions.
NAC plays an important role in your body’s detoxification process. It can help prevent side effects of environmental toxin exposure (3).
Doctors regularly give intravenous NAC to people with an acetaminophen overdose to prevent or reduce kidney and liver damage (
NAC helps detoxify your body and can treat acetaminophen overdoses.
NAC helps regulate glutamate levels, the brain’s most important neurotransmitter. While glutamate is required for regular brain activity, excess glutamate and glutathione depletion can cause brain damage.
This may contribute to mental health conditions such as bipolar disorder, schizophrenia, obsessive-compulsive disorder (OCD), and substance use disorder (
For people with bipolar disorder and depression, NAC may help decrease symptoms and improve quality of life. Moreover, research suggests that it may play a role in treating moderate to severe OCD (
Likewise, an animal study suggested that NAC may minimize the adverse effects of schizophrenia, such as social withdrawal, apathy, and reduced attention spans (
NAC may also have applications in managing substance use disorders. For example, preliminary studies show that NAC may decrease cannabis and nicotine use and cravings (
By regulating glutamate levels in your brain, NAC may alleviate symptoms of mental health conditions and reduce substance use and cravings.
NAC can relieve symptoms of respiratory conditions by acting as an antioxidant and expectorant, loosening mucus in your air passageways.
As an antioxidant, NAC helps replenish glutathione levels in your lungs and reduces inflammation in your bronchial tubes and lung tissue.
People with chronic obstructive pulmonary disease (COPD) experience long-term oxidative damage and inflammation of lung tissue, which causes airways to constrict, leading to shortness of breath and coughing.
Some studies suggest that taking NAC supplements can help improve COPD symptoms, exacerbations, and lung decline (
People with chronic bronchitis can also benefit from NAC. Bronchitis occurs when the mucous membranes in your lungs’ bronchial passageways become inflamed, swell, and shut off airways to your lungs (
By thinning mucus in your bronchial tubes and boosting glutathione levels, NAC may help decrease the severity and frequency of wheezing, coughing, and respiratory attacks.
In addition to relieving COPD and bronchitis, NAC may improve other lung and respiratory tract conditions — such as cystic fibrosis, asthma, and pulmonary fibrosis — as well as symptoms of nasal and sinus congestion due to allergies or infections (
NAC’s antioxidant and expectorant capacity can improve lung function by decreasing inflammation and breaking up mucus.
NAC’s ability to replenish glutathione and regulate brain glutamate levels can boost brain health.
The neurotransmitter glutamate is involved in a broad range of learning, behavior, and memory functions, while the antioxidant glutathione helps reduce brain cell oxidative damage associated with aging.
Because NAC helps regulate glutamate levels and replenish glutathione, it may benefit those with health conditions affecting the brain and memory (
Alzheimer’s disease slows down learning and memory capacity. Animal studies suggest that NAC may slow the loss of thinking ability in people with Alzheimer’s disease (
Parkinson’s disease is characterized by the deterioration of cells that generate the neurotransmitter dopamine. Both oxidative damage to cells and a decrease in antioxidant ability contribute to this disease.
NAC supplements appear to improve both dopamine function and disease symptoms such as tremors (
While NAC may improve brain health, more human research is needed to make firm conclusions.
By helping replenish the antioxidant glutathione and regulate glutamate, NAC has the potential to treat conditions such as Alzheimer’s disease and Parkinson’s disease.
In some cases, NAC has been shown to improve male fertility.
Approximately 15% of all couples trying to conceive are affected by infertility. In almost half of these cases, male infertility is the main contributing factor (
One condition contributing to male infertility is varicocele — when veins inside the scrotum enlarge due to free radical damage. In one study, 35 men with varicocele received 600 mg of NAC daily for 3 months after surgery. The combination of surgery and NAC supplementation improved semen integrity and partner pregnancy rate by 22% compared with the control group (
In addition, NAC may improve fertility in older women and those with polycystic ovary syndrome (PCOS) by inducing or augmenting the ovulation cycle, although more research is needed (
NAC may help improve fertility in men by reducing oxidative stress that damages or kills reproductive cells. It may also aid fertility in women with PCOS.
High blood sugar and obesity contribute to inflammation in fat tissue.
This can damage or destroy insulin receptors and increase the risk of type 2 diabetes (
Animal studies show that NAC may stabilize blood sugar by decreasing inflammation in fat cells and thereby improving insulin resistance (
When insulin receptors are intact and healthy, they properly remove sugar from your blood, keeping levels within normal limits.
By decreasing inflammation in fat tissue, NAC may reduce insulin resistance and improve blood sugar regulation, but human-based research is lacking.
Oxidative damage to heart tissue often leads to heart disease, causing strokes, heart attacks, and other severe conditions. NAC may reduce heart disease risk by reducing oxidative damage to tissues in your heart (
Studies show that NAC may protect heart function and heart health in people with diabetes and those recovering from certain heart surgeries (
NAC can reduce oxidative damage to your heart, which can, in turn, decrease your risk of heart disease.
NAC and glutathione also benefit immune health.
Research on certain diseases associated with NAC and glutathione deficiency suggests that supplementing with NAC might improve — and potentially restore — immune function (27, 28).
NAC’s ability to boost glutathione levels may improve immune function.
There is no specific dietary recommendation for cysteine because your body can produce small amounts.
For your body to make the amino acid cysteine, you need adequate amounts of folate, vitamin B6, and vitamin B12. These nutrients can be found in beans, lentils, spinach, bananas, salmon, and tuna.
While most protein-rich foods — such as chicken, turkey, yogurt, cheese, eggs, sunflower seeds, and legumes — contain cysteine, some people supplement with NAC to increase their cysteine intake.
NAC has low bioavailability as an oral supplement, meaning your body does not absorb it well. The accepted daily supplement recommendation is 600–1,800 mg of NAC (29).
NAC can be administered intravenously or orally, as an aerosol spray, or in liquid or powder form.
Eating high protein foods can provide your body with the amino acid cysteine, but you can also take NAC as a supplement to help treat certain conditions.
NAC is likely safe for adults when provided as a prescription medication.
However, high amounts may cause nausea, vomiting, diarrhea, and constipation. Inhalation of NAC solutions can cause swelling in the mouth, runny nose, drowsiness, and chest tightness.
People with bleeding disorders or taking blood thinning medications should not take NAC because it may slow blood clotting (
NAC has an unpleasant smell that makes it hard to consume. If you choose to take it, consult your doctor first.
While NAC is considered safe as a prescription medication, it can cause nausea, vomiting, and gastrointestinal disturbances, as well as mouth issues if inhaled.
NAC plays several important roles in human health.
Renowned for its ability to replenish levels of the antioxidant glutathione, it also regulates the important neurotransmitter glutamate. Additionally, NAC helps your body’s detoxification system.
These functions make NAC supplements a viable treatment option for multiple health conditions.
Consult your doctor to determine whether NAC may benefit your health.