Nonessential Micronutrient



NAC (the stable form of the amino acid cysteine) is a powerhouse of a supplement with potent antioxidant activity. In addition to combating exercise-induced damage to muscle tissue, it helps detoxify the liver, build connective tissue, fight viral infections, and combat the effects of age. And these are only the highlights!

Other names for NAC

n-acetylcysteine, cysteine, N-acetyl-L-cysteine, L-cysteine, acetylcysteine

Where to find NAC

NAC is the more stable supplement form of the amino acid cysteine. Food sources for cysteine include poultry, yogurt, oats, wheat germ, egg yolks, red peppers, garlic, onions, broccoli, and Brussels sprouts.


Why athletes use NAC

NAC is one of the most important antioxidants for an athlete — the benefits are numerous and the research rich. Its effect on muscle trauma caused by lifting weights or intense cardio training is exciting. A close second (and an occasional first) in importance would be its role in detoxifying the body and helping keep the liver in “like-new” condition. Its anti-aging benefits and ability to aid in joint health are great value add-ons.

Ways that NAC can enhance Muscle Gain & Recovery:
  • Stimulate strong connective tissue and even reduce pain from joint inflammation
Ways that NAC can enhance Longevity:
  • Fight free radicals, which is beneficial to post-exercise recovery


Signs of NAC deficiency

No deficiency conditions are known to exist.

Potential uses for NAC

Research indicates that NAC may be useful in the treatment of:

  • Overtraining
  • Addictions
  • Viral infections
  • Impaired respiratory function
  • AIDS
  • Aging


More about NAC

NAC is the supplemental form of the amino acid L-cysteine. Cysteine, when ingested as a supplement, is oxidized, which means it is “burned up” rather quickly by the body, rendering it useless. NAC is much more stable and does not suffer this fate — this is fortunate, as NAC is one powerhouse of a supplement with potent antioxidant activity.

The antioxidant properties of NAC have been shown to combat exercise-induced damage to muscle tissue, which is important for post-exercise recovery. It has been used successfully to detoxify the body, with emphasis on detoxifying the liver in cases of acetaminophen poisoning, and exerts the same properties to counter the effects of alcohol on the body. As cysteine, it is an integral part of the development and maintenance of strong connective tissue and the formation of skin and hair.

NAC is coveted for its anti-aging properties, most likely connected to its role in the substantial release of glutathione in the body, which fights the cellular damage of oxidative stress, a key to fighting against aging. Its ability to inhibit viral replication may be useful in fighting viral infections from HIV to the flu. And these are just the highlights on this potent antioxidant.

Post-exercise recovery

Supplementation with NAC (and other antioxidants) has been shown to illicit a protective effect on muscle and other related tissues after intense exercise. Much of this is due to its ability to increase (and preserve) glutathione levels. In a nutshell, this seems to combat the oxidative damage of exercise and help preserve muscle on a cellular level. This is a complex process (as is pretty much everything in our bodies), but the positive view is that in addition to aiding in recovery, consistent use may help maintain and even add muscle.

Detoxifying properties

As a premier anti-toxin and cell-membrane stabilizer, NAC helps neutralize the byproducts of ingested fats and alcohol metabolism and protect the body from the damaging effects of chemotherapy, cigarette smoke, heavy metals, and various other substances. It is one of the preferred methods for treating acetaminophen poisoning in Europe and is quite successful. Its liver-protecting benefits may make it useful for other liver conditions.

Connective tissue

NAC (as cysteine, which it becomes once in the body) is an integral component of connective tissue — tendons, ligaments, and the soft tissues that support our joints. Along with a number of other nutrients (like Vitamin C), it is actually part of the material that comprises the connective tissue. NAC is used by elite athletes who have suffered tears and partial tears of connective tissue as part of a post-surgery recovery strategy. In more mild cases, it can help reduce joint inflammation and the pain that goes with it.

The battle against time

Unchecked free radicals are also believed by researchers to be a major factor in the process of aging because they cause both cellular and DNA damage. Couple this with the fact that glutathione levels can drop by up to 35% as we age, and NAC, which both fights free radicals and increases glutathione levels, may help slow this “natural” process. It also has an impact in the formation of skin tissue.

Therapeutic uses

As with other nutrients that are believed to help boost immunity, NAC has been studied to see if it may help reduce the number of flu viruses or at least their severity. One study performed in Italy indicates that it may do just that. In this 6-month study, 25% of the people supplementing with NAC reported flu symptoms versus 79% in the placebo group.

NAC has been used since the 1960’s to help treat respiratory conditions by helping thin mucus and increase immunity and may be especially useful for people with chronic bronchitis, which is often associated with smoking. Preliminary studies indicate that NAC may also help increase levels of a type of immune cell called CD4+ in both healthy people and people with HIV.

In conclusion

If you’re an “elite athlete” who, while trying to stimulate muscle growth, blew a knee ligament while squatting 700 lbs and (sticking with the more is better philosophy) took a half a bottle of Tylenol to fight the pain, well, NAC may be your best friend!

Quite seriously, NAC is one of the most important antioxidants for athletes — the benefits are numerous and the research rich. Its effect on muscle trauma caused by lifting weights or intense cardio training is exciting. A close second (and an occasional first) in importance would be its role in detoxifying the body and helping keep the liver in “like-new” condition. Its anti-aging benefits and ability to aid in joint health are great value add-ons.



NAC is commonly found in 500-mg capsules with daily supplement levels ranging from 1 to 3 capsules daily.

Optimal levels are dependent on many variables, including amount of exercise and other specific situations when its ability to protect liver health may be important (like when you’re going to drink a few alcoholic beverages — not that anyone is endorsing that).


Some reports have indicated the upper limit for effective NAC supplementation is 2,000 mg daily. Amounts greater than this are not considered beneficial to use for extended periods.


NAC may be taken effectively with meals. There may be added benefits from taking NAC with other antioxidants, including Vitamin C and Vitamin E.

Synergists of NAC

Synergistic antioxidant benefits may be realized by supplementing NAC with Vitamin C in a 1 to 3 ratio. (For example, if you were to use 500 mg of NAC, you would supplement with 1,500 mg of Vitamin C.)

Safety of NAC

If you are pregnant or lactating, NAC is not recommended.

Anyone suffering from ulcers or similar conditions affecting the lining of the stomach may want to avoid NAC supplementation.

Toxicity of NAC

No known toxicity, although the benefits for extended use may peak at 2,000 mg daily.

Bans and restrictions

None reported.


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