Which Foods Contain N-Acetyl Cysteine (NAC)?

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:

• Brussels sprouts
• Broccoli
• Dairy products
• Eggs
• Garlic
• Legumes
• Meat, chicken, and turkey
• Nuts
• Oats
• Onions
• Red bell peppers
• Wheat germ
• Whole grains
• Yeast

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.