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The Smart Drug Beloved by Doctors, Nootropics Users and Anti-Vaxxers

NAC has been sold as a supplement since the 1990s, but in the face of its growing popularity, the FDA recently claimed that it’s actually a drug, leaving many worried about its accessibility in the future

If you spend any time in forums for nootropics, then amid the blitzkrieg of supplements with names that sound like nutrients for a supercomputer, you’re likely to see one particular smart drug pop up over and over again: NAC, or N-acetyl cysteine.

“I started taking NAC at 1g several days ago, and those several days have been profound,” boasts one person on r/nootropics, a subreddit with nearly 300,000 followers where members discuss a range of artificial and natural compounds thought to enhance cognitive function. “Profound” because for this 28-year-old, NAC has stymied his anxiety enough that “bad thoughts seem to roll off like water on a duck’s back.” 

Someone else claims that NAC helped him wean himself off of SSRIs with no side effects. And another person taking NAC who just got his latest lab results wrote that his “values are the best they have been in the past 5 years,” which he thinks is “proof that this stuff really works.”

But nine months ago, “this stuff,” started to disappear from online retailers and vitamin shops, leading people in nootropics forums scrambling to figure out why. 

NAC, which comes from the amino acid L-cysteine, is found naturally in the human body. It’s been around in one form or another since the 1960s, which was around the same time that Romanian psychologist Corneliu E. Giurgea coined the term “nootropics.” Eight years earlier, he synthesized a first-of-its-kind drug to help treat involuntary, irregular muscle twitches. His nootropic was called Piracetam, and it was hardly the miracle he thought it would be. But it carved out a field of study dedicated to drugs and supplements that, like NAC, profess to improve the way the brain functions.

Part of why NAC is so popular in the nootropics space is that when taken orally, which is how it’s commonly dosed, it typically has very few side effects. “There is no standardized daily dosage of NAC, but the most standard single dose is 600 milligrams, which can be given up to several times daily,” says Spela Salamon, a nuclear medicine resident at LKH Hochsteiermark State Hospital in Austria. In rare cases, NAC can cause gastrointestinal issues (heartburn, diarrhea, nausea and vomiting) or dry mouth. It’s not especially tasty either. But overall, NAC’s safety profile is about as dangerous as vitamin C. Among medical professionals, NAC has historically been used as a treatment for Tylenol poisoning.

In 2019, Salamon had a hunch that NAC was primed to become the next supplement du jour and suggested as much in a study she undertook. “The number of publications on NAC and the brain begins to spike in the early to mid-1990s,” she tells me. “This is also when articles on using NAC to treat neuropsychiatric and neurodegenerative disorders begin to emerge.” More recent research has theorized that NAC shows promise in helping to treat those suffering from schizophrenia and Alzheimer’s. “The results of trials where NAC was used to prevent or treat neurodegeneration are somewhat mixed, but promising,” Salamon adds.

Mixed because, according to Zhongcheng Shi, an immunologist at the Baylor College of Medicine, NAC wasn’t given orally in those studies. “So much more NAC may need to be taken orally to obtain high concentrations in the blood or neuro system,” Shi explains. That’s not to say that NAC isn’t a potentially effective nootropic. Only that its effectiveness in preventing and treating diseases of the brain warrants further investigation. 

But NAC has another well-known treatment profile, too — as an effective tool that can thin and loosen mucus in the lungs, making it easier for you to breathe. “NAC can also boost the immune system, suppress viral replication and reduce inflammation,” says Shi. As such, you probably won’t be surprised to learn that NAC is among the most common supplements to be included in what anti-vaxxers refer to as their “no COVID cocktail.” Alongside Quercetin, zinc, vitamin C and vitamin D, NAC is the over-the-counter supplement that people in diametrically opposed worlds — anti-vaxxers and medical professionals — take regularly. 

“We got the Pfizer vaccine about a year ago and take NAC daily,” says Shi of himself and his colleagues. Though he’s awaiting more data, he believes it can play a prominent role in preventing severe COVID infection. In fact, during the spring of 2020, before effective vaccines for COVID-19 were developed, and when the scientific community was racing against the clock to find existing medicines to treat the virus, Shi proposed NAC as potentially helpful. So did several other studies.

Researchers in Greece even suggested that NAC may reduce the need for mechanical ventilation and mortality in patients hospitalized for acute respiratory COVID. “Those papers may have promoted NAC usage, to some degree, especially in people who are hesitant to be vaccinated,” says Shi. 

What happened next is tougher to explain. On July 29, 2020, the Food and Drug Administration (FDA) issued warning letters to seven companies that claimed to cure, treat, mitigate or prevent hangovers with NAC. The evidence in favor of those claims is anecdotal at best, but that’s beside the point. Per the FDA, the reason NAC was being targeted was that the product couldn’t be lawfully marketed as a dietary supplement because, when it was first introduced into the market in 1963, it was categorized as a drug. In compliance with the FDA’s warning, Amazon began removing NAC from its website in May 2021. 

Needless to say, that set off a digital firestorm. Last December, the Natural Products Association (NPA) filed suit against the FDA, calling the agency’s actions to “retroactively” apply the drug-exclusion clause of the Federal Food, Drug and Cosmetic Act to ban NAC in dietary supplements unlawful. The NPA claimed that NAC meets the definition of a dietary supplement because there’s evidence showing NAC was marketed in the U.S. food supply since 1991, before the drug-exclusion clause became law. Not to mention, the FDA has never exercised such authority, though it has zoned in on some ingredients — one example being CBD. In other words, the FDA didn’t seem to care that NAC was categorized as a dietary supplement until it became so popular. 

“I can’t make heads or tails of why they picked this ingredient,” says Daniel Fabricant, CEO and President of the NPA. “It would be a shame if this was done just to prop up pharma IP.”

All of which may be much ado about nothing if further studies show that NAC is neither an effective nootropic nor helps prevent a severe COVID infection. But according to Salamon, that’s not likely to be the case. She thinks NAC is primed to gain more relevance as we continue to find out about the damage that even mild cases of COVID can do to the nervous system. “We know [COVID] can cause both physiological brain changes — for example decreased glucose metabolism — as well as cognitive deficits and a decrease in IQ following a COVID infection,” says Salamon.

She’s also concerned about the long-term prognosis of these changes and their potential to contribute to neurodegenerative diseases like Parkinson’s or Alzheimer’s. “NAC could offer a possible treatment option in this case, but more studies are needed,” Salamon explains. Along those lines, she’s sure to add that vaccines are still the most effective way to mitigate COVID infections. “Supplements, no matter how effective, can only play a minor role in the entire story,” she says. 

Meanwhile, in case the FDA does decide to label NAC a prescription drug, those in the nootropics subreddit are already making other arrangements. One subscriber who works at a Vitamin Shoppe in Michigan tells me that ever since the FDA’s ruling, they can’t keep the supplement on their shelves. “There have been talks of NAC becoming a prescription drug so people are buying them up just in case that happens,” he says. “Right now, it’s less than $50 a bottle, and no one wants to pay $300 a bottle and have to see a doctor if it becomes a prescription.”

Someone else writes on the subreddit that when he went to a Vitamin World, there were only two bottles left. “Shelves were bare,” he laments. Another adds, “Hard not to freak out when it’s no longer available from multiple supplement manufacturers such as NOW Foods and what little is left is in offline retail stores.” 

What’s all but certain is that this story is in the to-be-continued stage. The health-care system is failing. Americans are increasingly disillusioned with professional diagnoses and trying to find their own. Anti-vax groups are reaching for everything from nootropics to medications for parasitic disease to self-treat COVID symptoms. And federal agencies like the FDA are born to overreach.

None of this, of course, bodes well for those interested in NAC. Not the medical professionals like Salamon and Shi who are trying to gauge whether it’s a viable treatment for myriad afflictions — and definitely not for the nootropics devotees who insist that their favorite smart drug is the real deal.