What’s the Best NAC Supplement? Experts Weigh In (2024)

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The vitamin aisle can be a little, well, extra these days. With supplements claiming to help with everything from focus to performance, it can be hard to tell which are actually worth adding to your stack. NAC is a lesser-known supplement, but “people who are looking for ways to reduce their susceptibility to acute and chronic health conditions might consider supplementing with it,” says registered dietitian Jeanette Giacinto, R.D., C.D.N. The amino acid helps to produce a powerful antioxidant that can help combat inflammation caused by certain conditions (1). But, how do you go about picking out the best NAC supplement?

About the Experts:

Jeanette Giacinto, M.S., R.D., C.D.N., a registered dietitian and nutrition consultant for Bodybuilding Reviews. Giacinto provides nutrition and wellness coaching to those looking for a holistic, root cause approach to health.

Joanne Slavin, Ph.D., R.D., a professor in the Department of Food Science and Nutrition at the University of Minnesota. Slavin has authored more than 350 scientific articles on dietary fiber, carbohydrates, whole grains, protein, snacking, gut health, brain health, and sustainable agriculture—and was a member of the 2010 Dietary Guidelines Advisory Committee.

What Is NAC?

NAC stands for N-Acetyl Cysteine. “NAC is the supplement form of the amino acid cysteine, which the body uses to make a powerful antioxidant called glutathione,” Giacinto says.

Antioxidants like glutathione put up a fight against harmful compounds in your body called free radicals, which damage cell membranes and DNA, and cause oxidative stress. An imbalance between antioxidants and free radicals can damage tissues and contribute to cancer, heart disease, and premature aging.

Your body makes cysteine from another essential amino acid, methionine. Cysteine is also found in high-protein foods like ricotta, cottage cheese, yogurt, pork, chicken, turkey, wheat germ, and oat flakes. Rich sources of methionine include nuts, beef, turkey, pork, fish, and eggs (2).

What does NAC do?

NAC has traditionally been used to prevent side effects from drug reactions and toxic chemicals. For instance, it’s often given via an IV for people who have taken too much acetaminophen (Tylenol) to help avoid liver and kidney damage (1).

Athletes use NAC for its ability to reduce oxidative damage from exercise and potentially improve physical performance (3).

Plus, there’s growing interest around the possible benefits NAC supplementation can have on your mental health—specifically, reducing symptoms of anxiety, notes registered dietitian Joanne Slavin, Ph.D., R.D.

Potential Benefits of NAC

Here are just a few of the perks you may experience by trying a NAC supplement.

Improved mental health

Although studies on NAC in the treatment of mental health conditions have generally shown mixed results, one review published in 2022 found that NAC supplementation may improve symptoms of depression, schizophrenia, severe autism, and obsessive compulsive disorders (4).

In one recent study, people with major depressive disorder who took 2,000 milligrams per day of NAC didn’t notice any significant changes in their symptoms at the end of the study (at week 12). But they did have less depressive symptoms, more confidence in their relationships, and better day-to-day functioning four weeks later (at week 16)—even after discontinuing it. This was especially the case for those who reported severe depressive symptoms at the start of the study (5).

Another recent study found that taking NAC for eight weeks reduced anxiety symptoms in those with multiple sclerosis (MS) (6).

“If you’re looking for an antioxidant and potentially some relief from mental health conditions, there is some data that suggests it might work for people,” says Slavin.

Improved athletic performance

Commonly known as a sports supplement, research suggests NAC can help improve exercise performance, antioxidant capacity, and glutathione balance. It’s considered a safe and low-risk supplement for athletes (2).

“There has been some research to show that supplementation with NAC may improve exercise performance, but more research is needed to support these claims,” says Giacinto.

One very small-scale study—consisting of 10 seasoned triathletes—found that taking NAC supplements for just nine days helped participants post faster times on the bike. Researchers also noted there was a reduction in exercise-induced oxidative damage among the athletes, which suggests NAC supplementation may help promote muscular adaptation in endurance training (7).

Supports brain health

Research suggests that NAC may be helpful as a therapy in combination with more standard treatments for neurodegenerative diseases such as Parkinson’s disease and Alzheimer’s disease, nerve pain, and stroke (8).

Oxidation and neuroinflammation can affect your ability to understand and learn things in a variety of ways—which may explain NAC’s brain benefits.

Studies showing that NAC can influence human cognition are promising, but also inconsistent. “NAC may reduce effects of traumatic brain injuries, and improve outcomes in Parkinson’s disease, but more research is needed,” says Giacinto.

Slavin is interested in NAC’s potential to replace certain types of drugs for mental health conditions. More research is needed, but if it’s proven to be effective, it’s a less risky option than some more potent drugs for mental health conditions, Slavin says.

“There might be some advantages as far as feeling better or being able to reduce other medications, so I think that’s probably the most promising thing,” Salvin adds.

Protects kidneys

NAC may reduce the progression of chronic kidney disease, says Giacinto.

A 2023 study found that people with chronic kidney disease who took NAC had a significantly lower rate of dialysis (treatment for kidney failure) than non-NAC users (9). NAC appears to regulate two important measures of kidney function: serum creatinine (SCr) levels and estimated globular filtration rate (eGFR).

What to Look for In NAC Supplements

The standard dose for NAC is 600 mg, which can be taken once or twice a day, depending on your needs, says Giacinto.

Research suggests higher doses of NAC (1,200-1,800 mg daily) may be beneficial. Experts typically recommend taking 600 mg at different times throughout the day simply because that’s how studies on the supplement have been conducted, according to Giacinto.

Look for options that undergo third-party testing, which can help ensure you’re taking a high-quality (and safe) supplement.

“Look for the NSF certification seal,” Giacinto adds. “USP is another company that tests supplements—USP verification means that the product was made in a clean and controlled facility.”

Ingredients to avoid

As is the case with any supplement, there are some ingredients you’ll want to avoid if possible.

For instance, skip any supplements that have titanium dioxide—a filler that can accumulate in your body and damage DNA, according to Giacinto.

Also, consider steering clear of any pills that contain sodium benzoate, which increases the shelf life at the expense of causing gastrointestinal issues. “It’s even considered carcinogenic in combination with vitamin C,” adds Giacinto.

NAC Supplement Side Effects

Research indicates that taking more than 600 mg per day may cause nausea, skin redness, and itching for some people (10). Touch base with your doctor to see if taking NAC supplements could interfere with any other medications you’re currently on.

“Generally, when you’re looking at the amounts [of NAC] that people are taking in a dietary supplement, it’s probably not very risky,” says Slavin. “If people believe it helps them, I think it’s OK.”

The Best NAC Supplements, According to Experts