What is N-Acetylcysteine and How Can it Help the Body?

What is N-Acetylcysteine and How Can it Help the Body?

By: Holly L. Thacker, MD • Posted on January 06, 2021

What is N-acetylcysteine?

N-acetylcysteine (NAC) is a supplement form of the semi-essential amino acid cysteine. An essential amino acid HAS to be ingested as the body cannot make it on its own.

Whereas a semi-essential amino acid can be made in the human body. For example, the body can make enough cysteine if there is enough serine and methionine in the body. Serine is an amino acid supplied from food or synthesized by the body. Methionine is an amino acid found in proteins in foods and proteins found in the tissues and organs of our body.

L-methylfolate supports methionine being converted to serotonin, an important neurotransmitter. Amino acids are the building blocks of proteins and neurotransmitters in the body.

Most people ingesting a healthy diet can make enough of the semi-essential amino acids and/or can directly ingest cysteine.


Cysteine is present in high protein foods such as:

  • chicken
  • turkey
  • eggs
  • legumes
  • cheese
  • yogurt
  • sunflower seeds

Cysteine is critical for replenishing one of the most powerful anti-oxidants in your body - Glutathione and one of the most important neurotransmitters in the body - Glutamate.


Anti-oxidants are important for taking care of free radicals in cells. Glutathione is one of the body’s most important anti-oxidants that protects the liver and kidneys, which are the body’s powerhouses for cleaning up toxins and metabolizing medications and hormones.

In fact, Glutathione is given intravenously to treat acetaminophen (Tylenol®) overdoses. It doesn’t take too much acetaminophen to kill your liver. Alcohol plus acetaminophen is a dangerous combination.

Many medications needed to treat medical conditions as well as medical conditions themselves, like Diabetes Mellitus type 2 can be hard on the liver and kidneys.


Glutamate is an important neurotransmitter in the brain that is supported by NAC. If a person is low in both glutathione and glutamate, there can be neuropsychiatric disorders, including:

  • Depression
  • Obsessive Compulsive Disorder (OCD)
  • Parkinson’s disease

Adults over age 50 with word finding difficulty may have a myriad of problems:

  1. Menopause/low estrogen in menopausal women which can reduce acetylcholine in the brain leading to ‘brain fog.’
  2. Low B12 levels from dietary issues of GI malabsorption from Pernicious Anemia requiring B12 shots.
  3. Obstructive Sleep Apnea that lower’s blood oxygen levels at night damaging the brain and cardiovascular systems.
  4. Undiagnosed and/or untreated problems like hypertension, diabetes, and depression can lead to symptoms that overlap with brain fog.
  5. Nutritional deficiencies including vitamin D and zinc can affect brain function.
  6. Sleep disorders are common, but treatable.

If conditions are evaluated and treated, but the symptom of 'brain fog' persists, you may want to discuss trying a methylated vitamin combination with NAC such as CerefolinNAC® (only available as a prescription) or El Folate Plus® (available over-the-counter and online without a prescription).

In addition to these combinations, it's important to have a healthy MIND diet. Diet, exercise and selected vitamin use to boost glutamate may help improve minor cognitive problems that many midlife and beyond adults frequently report.

Lung Conditions

Lung disorders including Chronic Obstructive Pulmonary Disease (COPD), asthma, cystic fibrosis and COVID-19 lung inflammation may be helped by replenishing glutathione levels via NAC supplementation.

Other Conditions

Research is ongoing to see if there is a role for NAC supplementation for other conditions, including:

Recommended NAC Dosage

The is no Recommended Daily Allowance (RDA) for NAC because cysteine is a semi-essential amino acid and your body has the ability to make cysteine especially with enough folate, B6 (pyridoxine) and B12 (methylcobalamin).

It is available over the counter in 600mg oral dosage and can be prescribed intravenously by a physician as well as via aerosol.

A healthy diet, exercise and medical control of any medical conditions are your first line of defense. Selected vitamins and supplements may be indicated after careful consideration by you and your physician.

Be Strong, Be Healthy, Be in Charge!

-Holly L. Thacker MD

Holly L. Thacker, MD, FACP is nationally known for her leadership in women’s health. She is the founder of the Cleveland Clinic Women’s Health Fellowship and is currently the Professor and Director of the Center for Specialized Women’s Health at Cleveland Clinic and Lerner College of Medicine at Case Western Reserve University. Dr. Thacker is also the Executive Director of Speaking of Women’s Health and the author of The Cleveland Clinic Guide to Menopause. Her special interests and areas of research including menopause and related medical problems including osteoporosis, hormone therapy, breast cancer risk assessment, menstrual disorders, female sexual dysfunction and interdisciplinary women’s health.

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