Which Foods Are Highest in N-Acetyl Cysteine (NAC)?
Diet & NutritionNutrients & Supplements

Which Foods Contain N-Acetyl Cysteine (NAC)?

While no food is a source of NAC, a number of healthy options can provide the amino acid cysteine.
Which Foods Contain N-Acetyl Cysteine (NAC)?
Everyday Health
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Updated on October 27, 2025
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N-acetyl cysteine (NAC) is a drug approved by the U.S. Food and Drug Administration to help reduce the thickness of mucus and ease its removal as well as to reverse acetaminophen toxicity. Also sold as a dietary supplement in the United States, NAC is gaining popularity due to its powerful antioxidant properties.

While NAC is only available in supplement form, the body converts the compound into the amino acid cysteine, which is found naturally in a number of healthy foods. Cysteine is more reactive and less bioavailable than NAC, but there may be health benefits associated with consuming cysteine-rich foods.

NAC vs. Cysteine vs. Cystine: What’s the Difference?

You may hear NAC referred to as N-acetyl cysteine, cysteine, or even cystine, so it may be helpful to understand the nuances between the three.

NAC is a supplement derived from the amino acid cysteine. It largely converts into cysteine as it’s metabolized and used by the body.

Composed of two cysteine molecules bonded together, cystine is the oxidized form of cysteine. Cystine from food sources is absorbed less efficiently in the small intestine than cysteine due to its lower digestibility.

Because cysteine is a conditional amino acid, one that’s only considered essential when you’re sick or under excess stress, there isn’t a recommended daily intake associated with this particular nutrient.

Potential Health Benefits of NAC and Cysteine

Emerging research suggests that NAC may provide several health benefits beyond serving as an effective treatment for drug-induced liver toxicity from acetaminophen poisoning.

NAC is a mucolytic, a medication that helps thin and loosen mucus in people with certain respiratory conditions.

While human subject clinical research is limited, a number of studies explore NAC’s powerful antioxidant properties and its ability to prevent oxidative stress as well as reduce the effects of existing oxidative stress. For this reason, some healthcare providers use NAC alongside other medications to help treat some diseases and conditions related to oxidative stress and inflammation, including polycystic ovary syndrome (PCOS), ulcerative colitis, and neurodegenerative diseases like Alzheimer’s and Parkinson’s.

While its benefits are still being explored, NAC appears to be both a safe and well-tolerated supplement, without any considerable side effects noted in research thus far.

Foods Highest in Cysteine

While NAC is only available in supplement form, some of the best food sources of cysteine include:

For optimal health, enjoy a well-rounded diet with a variety of these nutritious, amino acid–rich foods. And if you’re interested in exploring NAC supplementation, consult your healthcare provider to learn how it may serve you and your specific needs.

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Reyna Franco, RDN

Medical Reviewer
Member of American College of Lifestyle Medicine

Reyna Franco, RDN, is a New York City–based dietitian-nutritionist, certified specialist in sports dietetics, and certified personal trainer. She is a diplomate of the American College of Lifestyle Medicine and has a master's degree in nutrition and exercise physiology from Columbia University.

In her private practice, she provides medical nutrition therapy for weight management, sports nutrition, diabetes, cardiac disease, renal disease, gastrointestinal disorders, cancer, food allergies, eating disorders, and childhood nutrition. To serve her diverse patients, she demonstrates cultural sensitivity and knowledge of customary food practices. She applies the tenets of lifestyle medicine to reduce the risk of chronic disease and improve health outcomes for her patients.

Franco is also a corporate wellness consultant who conducts wellness counseling and seminars for organizations of every size. She taught sports nutrition to medical students at the Albert Einstein College of Medicine, taught life cycle nutrition and nutrition counseling to undergraduate students at LaGuardia Community College, and precepts nutrition students and interns. She created the sports nutrition rotation for the New York Distance Dietetic Internship program.

She is the chair of the American College of Lifestyle Medicine's Registered Dietitian-Nutritionist Member Interest Group. She is also the treasurer and secretary of the New York State Academy of Nutrition and Dietetics, having previously served in many other leadership roles for the organization, including as past president, awards committee chair, and grant committee chair, among others. She is active in the local Greater New York Dietetic Association and Long Island Academy of Nutrition and Dietetics, too.

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Kim Grundy, PT

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Kim Grundy is a physical therapist, as well as an experienced health and fitness writer that has been published in USA Today, SheKnows, Brides, Parents and more. She graduated from the University of Oklahoma and lives with her husband and kids in Florida. She has treated patients with chronic conditions, as well as athletes in the outpatient setting that are working towards recovering from an injury. Kim is passionate about sharing her knowledge of health and fitness with others.

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