These days, it’s fairly common in medicine for a drug to be developed to treat one condition which then turns out to have broader application. Take metformin or rapamycin for example, both prescribed for specific conditions, which now show promise as longevity-enhancing compounds. But these are powerful pharma drugs, with more likelihood of side-effects, and which should only be taken under the supervision of a physician. But how about a supplement that has been used for decades to treat a couple of specific problems – like acetaminophen (Tylenol) overdoses and mucus buildup. And which subsequent research has confirmed helps push back against the basic processes that drive aging, and consequently looks like it helps treat the diseases of aging that ultimately hobble or end most of our lives. With negligible side-effects. That would be something, right? Well, if you’re not familiar, let me introduce you to N-Acetyl Cysteine or NAC. 

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OK, so the reality is, nothing you buy in the health food store is as essential to your healthspan as the lifestyle basics: clean diet, good sleep habits, managing stress effectively, and getting plenty of movement. But adding certain supplements to those lifestyle essentials can give you an edge, help fill in the nutritional gaps and tilt the longevity odds more in your favor. That’s why NAC has become one of the most exciting all-purpose anti-aging supplements on the market – and I recommend it to many of my patients looking to support better longevity prospects. Here’s a look at this incredibly helpful supplement and what you need to know about it:

So, what is NAC, exactly?

NAC is the supplement form of cysteine which is an amino acid that we get from protein-rich foods like eggs, meat and dairy. Cysteine’s gotta-have-it superpower is that it helps make glutathione, the body’s single most powerful antioxidant compound which does a world of good things like helping clear toxins from the body and building up the immune system. But taking cysteine as supplement doesn’t work because we break it down in the gut. But, with a little wizardry in the lab, cysteine can be synthesized into NAC which is far more stable and, inside the cells of the body, fuels the production of more cysteine which means a more generous glutathione supply. And it’s when cells are under stress, for instance, during an illness or when we’re simply pushing into late middle age or elderhood, that we most need ample glutathione stores. 

Class is in session: NAC 101 

Emergency medicine doctors have been using NAC to treat acetaminophen overdoses since the late ‘70s. That was a good indication that the compound had broader detox powers inside the liver which is, after all, the organ most responsible for neutralizing toxins that build up in the body. More recent research is showing that NAC has the potential to combat two common and sometimes lethal liver, non-alcoholic fatty liver disease and alcoholic liver disease. 

From liver to lungs...

The other established use of NAC has been for treating the buildup of mucus in the lungs. We’re not talking congestion from a winter cold here. It’s been used, especially in Europe, to treat a variety of serious lung diseases: COPD, cystic fibrosis, bronchitis, asthma. One 2023 academic review showed that NAD reduced the frequency of COPD flare-ups.  

NAC for everything? 

What’s become clear over time is that NAC’s therapeutic effect inside the liver and the lungs -- by helping to build up the body’s glutathione stores -- can help push back against the “hallmarks of aging” that were driving aging in just about every system of the body. It can reduce “oxidative stress” – that is, the “free radicals” that rust the body from the inside out – and lower levels of chronic inflammation and help counter the age-related functional declines in our immune system and in the mitochondria, the powerplants of the cell. These properties make NAC a promising candidate for treating diseases related to oxidative stress and inflammation. That’s a lot of territory, which translates into a lot of possible clinical applications. True, much of the research has been done in animal models but the body of clinical, that is, human, research is growing. It would be growing a lot faster if Big Pharma could generate patents from it, and make a ton of money, but that’s another story. Still, the list of diseases where we have good preliminary evidence that NAC can make a difference is impressive. 

NAC and your aging brain.

Interestingly, one area where there has been a good amount of clinical research is in psychiatric disorders and neurodegenerative diseases. The evidence is mixed but in roughly half the studies that have looked at Alzheimer’s, autism, schizophrenia, bipolar disorder, as well as cannabis and cocaine addiction, NAC therapy had a positive effect. The supplement seems to target brain inflammation and problems with brain hormones like dopamine which are associated with a range of brain-related disorders. 

Help for your immune system.

One of the nasty facts of life is that as we head into the senior years, our immune systems wear down. That can manifest in different ways. We are likely to get more respiratory infections and we’re more vulnerable to autoimmune conditions and to cancer. Here the evidence suggests that NAC can give our infection-fighting T cells a boost and slow down the replication of viruses in our system, in addition to helping keep the liver and the lungs running as smoothly as possible, always a plus. In one older European study, elderly subjects who took NAC had significantly fewer cases of the flu and milder symptoms when they did succumb. More recent research has looked at NAC as an ally in the fight against HIV and COVID, with more mixed results. 

Inflammaging: calling NAC!  

As I think many of my readers know by now, chronic inflammation lies at the heart of our diseases of aging – everything from atherosclerosis to Alzheimer’s – and we can even think of it as a driver of the aging process itself. Again, here too, NAC can lend a hand. We have studies that show that administering NAC can suppress inflammatory proteins, called cytokines. In one such study, NAC reduced markers of inflammation and oxidative stress in elderly patients who were going under surgery. From there, of course, it’s a jump to actually show that NAC reduces inflammation-driven disease. To date, our evidence is mostly in animals, studies that show improvement, for instance, in atherosclerosis and diabetes. But in one human observational study, following almost 47,000 people with type 2 diabetes, NAC users had a 39% lower risk of having a major cardiac event than non-users. A hint that we’re on the right path: in several animal studies involving worms, flies and mice, NAC extended lifespan by 20-30%, with a stronger effect found in stressed or aged animals. 

Is NAC safe? 

Yes, that’s one of its one of its biggest selling points – it’s even landed on the World Health Organization “Essential Medicines” list. There are some common, mild effects, such as nausea, diarrhea and headache. And there have been some rare allergic reactions reported, especially with IV use, but for most people, it’s pretty well tolerated when taken as directed, and with the OK from your doc.

What about dosage? 

Most of the studies looking at NAC for general antioxidant support used dosages in the 500-1,500 mg range. That’s a useful benchmark. Studies that looked at psychiatric or respiratory conditions often lifted the dosage up to 3,000 mg a day but before considering supplementing at that higher range, or for that matter, even in the lower ranges, consult with your health care provider to be sure it doesn’t conflict with any other meds you may be on.