Food Sources of N-Acetyl Cysteine

N-Acetyl Cysteine, or NAC, has gotten lots of buzz recently for all of its potential health benefits. While NAC is only available in supplement form, this amino acid is found naturally in foods in its cysteine form. Get the scoop on the best cysteine foods to incorporate into your diet.

You may hear NAC being referred to by its full name, N-Acetyl Cysteine, or just as cysteine or even cystine. So what is the difference between them? Cystine is actually made up of two cysteine molecules bonded together and, according to the USDA, cysteine and cystine are nutritionally equivalent. These amino acids are both found in high-protein foods.

Now that we have the cysteine versus cystine confusion handled — what about NAC? N-Acetyl Cysteine, or NAC, is the supplement form of the amino acid cysteine, so even though you can't eat N-Acetyl Cysteine foods, you can eat cystine or cysteine foods.

The USDA lists the recommended daily intake of the amino acid cystine as 1.9 mg per pound of body weight, so someone weighing 150 pounds should aim for 285 mg of cystine per day. They don't give the requirement in its cysteine form. Dietary supplements, like NAC, are not regulated by the FDA in the same way that food is, so there is no recommended daily amount. Talk to your doctor about the dose that is right for you.

Read more: What Amino Acids Do Vegans Tend To Lack?

The benefits of NAC supplements have been widely studied, and it has shown favorable results for health. A March 2014 study in The Lancet Respiratory Medicine showed that patients who had moderate to severe COPD who took 600 mg of NAC twice daily had fewer exacerbations.

An April 2017 review of NAC in Cell Journal went on to show that it has positive effects on many other health conditions, including chronic bronchitis, Alzheimer's and preterm birth. They also concluded that it is a safe and tolerable supplement, without any significant side effects.

Since there aren't any N-Acetyl Cysteine foods, are there benefits to eating cystine or cysteine foods instead of taking supplements? The USDA reports that the amino acid in its cystine form can help with hair health, and is a great antioxidant. A March 2018 study in Molecules looked at the amino acid in its cysteine form and concluded that, although much of the benefits and research were focused on NAC, the studies on cysteine also showed promising health benefits, including antioxidant properties, hair growth and strengthening, a boost in immune system performance, enhanced stroke prevention and decreased incidence of cancers of the gastrointestinal tract.

Read more: Breaking Down Amino Acid Supplements

According to the USDA, these are the top 10 foods containing the most amino acids in the cystine form:

1. Lean Pork Chops
2. Skirt Steak Beef
3. Lean Chicken Breast
4. Tuna
5. Lentils
6. Oatmeal
7. Eggs
8. Low-Fat Yogurt
9. Sunflower Seeds
10. Swiss Cheese

In addition, an April 2015 study in the Stroke journal reports that eating a diet rich in cysteine foods, including chicken, turkey, garlic, yogurt and eggs, showed a decreased risk for strokes.

For optimal health, enjoy a well-rounded diet with plenty of these nutritious and amino-acid-rich foods. Even though its not possible to find N-Acetyl Cysteine foods in that specific form, talk to your doctor about taking the NAC supplement for further health benefits.