Health Hotline Magazine | February 2026

What Is It? N-acetylcysteine, or NAC, is an amino acid, cysteine, with an acetyl group attached to it, which makes it more bioavailable. More importantly, it acts as a building block for a vital antioxidant made by our bodies—glutathione. This internally-made, or “endogenous,” antioxidant has many critical roles: it is present in all the cells in our bodies, where it protects them from free radical damage (i.e., oxidative stress); it helps detox heavy metals like mercury and lead; it helps regenerate the antioxidant vitamins E and C; it’s critical for normal detoxification in the liver and kidneys; and is vital for mitochondrial health, the energy-making “machines” in our cells. When glutathione levels are low, health issues arise. Glutathione depletion is implicated in chronic diseases like Alzheimer’s and Parkinson’s, lung and liver diseases, cardiovascular disease, age-related diseases like macular degeneration and arthritis, and even the “aging process itself.” But if our bodies make glutathione, why do we need NAC? It’s pretty simple: Our modern lives, punctuated with diets of ultra-processed foods, lack of quality sleep, chronic stress, exposure to environmental toxins, drinking alcohol, smoking, and even the aging process, continuously deplete glutathione levels. On top of that, some people just can’t e ciently make enough of it. NAC provides a bioavailable form of cysteine that is rapidly absorbed by cells, where it is used to make glutathione, e ciently increasing and maintaining levels. And this is where the benefits begin.

NAC Is One of Your Best Defenses During Cold & Flu Season By increasing glutathione levels, NAC naturally benefits immunity, but research has shown that NAC itself has a balancing effect on the immune system and helps to counteract age-related decline in immunity. A recent study supplemented 36 healthy postmenopausal women (50 and older) with 600mg of NAC daily for four months. At the end of four months, there was a significant improvement in immune cell function, a reduction in inflammatory cytokines, and increases in glutathione levels inside immune cells, bringing the older women’s immune function closer to that of the younger control group (women 30-49 years old). The benefits were still measurable three months after the end of the supplementation, suggesting that NAC has a lasting effect. Other research has suggested that NAC has the ability to interfere with the flu virus’s ability to replicate and spread. In fact, when it comes to fighting the flu, NAC may just be one of our best defenses. One placebo-controlled study including 262 men and women 65 and older found that 600mg of NAC twice daily for six months (during flu season) resulted in “a significant decrease in the frequency of influenza-like episodes, severity, and length of time confined to bed. Both local and systemic symptoms were sharply and significantly reduced in the NAC group.” And more recently, research is finding that NAC can play a protective role during COVID infection, due in part to its antioxidant, anti-inflammatory, and immune-balancing effects, which helps counteract the excessive immune activation, increased inflammation, and the oxidative damage COVID causes. Preliminary research also indicates that NAC may be able to interfere with the virus’s ability to replicate.

When it comes to fighting the flu, NAC may just be one of our best defenses

Our Lungs Love NAC! NAC was first discovered to have mucolytic—mucus thinning—properties in the 1960s, leading to a burst of research specifically looking at its effect on pulmonary diseases, diseases that affect the lungs. Since then, the research has expanded and found that NAC is beneficial in other chronic respiratory issues, like chronic obstructive pulmonary disease (COPD), and also protects our lungs from environmental toxins like air pollution. Like any chronic disease, lung disease has an underlying factor of excessive oxidative stress and inflammation, which depletes glutathione reserves in lung cells and damages delicate tissues. The respiratory system is particularly susceptible to oxidative injury, both from the high levels of oxygen in the lungs as well as from external pollutants like cigarette smoke, wildfire smoke, and diesel exhaust, which also increase inflammation. NAC directly counteracts this with its ability to replenish glutathione levels, restoring antioxidant balance. In clinical settings, it has been shown that oral administration of 600mg of NAC for five days significantly increased glutathione levels in lung fluid. Chronic obstructive pulmonary disease (COPD) is caused by damage to the airways, which leads to inflammation and restricted air flow, making it hard to breathe. It’s most often caused by smoking, but can also be caused by long-term exposure to other fumes, smoke, or chemicals. The most common types are chronic bronchitis and emphysema. Multiple studies have found that daily supplementation with 600-1,200mg of NAC reduces harmful free radicals and inflammatory markers and significantly reduces flare-ups in subjects with COPD. A 2024 meta-analysis, including 20 randomized, controlled trials and 4,044 subjects with either chronic bronchitis or some other form of COPD, evaluated the effects of daily supplementation with NAC (doses ranged from 400-3,600mg). The subjects treated with NAC experienced fewer flare-ups, significantly fewer symptoms, and overall better quality of life. Another study investigating NAC and chronic bronchitis found that 400mg per day administered during the winter months lead to a significant reduction in flare-ups, a significantly smaller percentage of “sick days” from work, and lower rates of hospitalizations. Exposure to air pollution, like wildfire smoke or car exhaust, can lead to the same damage as chronic lung disease—increases in oxidative damage and inflammation and reductions in glutathione. The research in this area is still fairly new, but results so far are promising. A 2022 study found that NAC reduced lung injury caused by fine particulate matter in exposed mice, reducing oxidative damage and lung inflammation. Fine particulate matter is particularly harmful because it can infiltrate deep into the lungs; one common source is car exhaust. A placebo-controlled trial including 13 patients with mild asthma found that 600mg of NAC three times a day, taken for five days leading up to exposure, reduced the oxidative damage and inflammation caused by diesel exhaust.

32 | Health Hotline ®