NAC & Glutathione: What the Science Actually Says About Liver Detox

N-Acetyl Cysteine (NAC) is arguably the most evidence-backed ingredient in the liver supplement category — and yet it appears in fewer than 40% of the products we reviewed. Here is why that matters.

What Is NAC and Why Does the Liver Need It?

NAC is a precursor to glutathione — often called the body's "master antioxidant." Glutathione is produced in the liver and is the primary molecule responsible for neutralising reactive oxygen species (ROS), conjugating toxins for excretion, and protecting liver cells from oxidative damage.

The problem is that glutathione cannot be effectively supplemented directly — it is broken down in the digestive tract before it reaches the bloodstream. NAC bypasses this limitation by providing cysteine, the rate-limiting amino acid in glutathione synthesis. Once absorbed, NAC is converted to cysteine, which the liver uses to produce glutathione on demand.

What the Clinical Evidence Shows

The clinical literature on NAC and liver health is substantial. A landmark 2011 study published in Hepatology demonstrated that NAC at 600mg/day significantly reduced ALT and AST enzyme levels — the primary markers of liver inflammation — in patients with non-alcoholic fatty liver disease (NAFLD) over a 12-week period.

A 2010 meta-analysis in the Journal of Gastroenterology and Hepatology reviewed 12 randomised controlled trials and concluded that NAC supplementation consistently reduced markers of oxidative stress in patients with chronic liver disease.

Crucially, NAC is also the standard-of-care treatment for acetaminophen (paracetamol) overdose — administered intravenously in emergency settings to prevent acute liver failure. This clinical application underscores the mechanism's validity at a fundamental level.

The Correct Dose

The studied therapeutic range for liver health is 350–600mg of NAC per day. Many supplements include NAC at 100–200mg — a dose that may be insufficient to meaningfully raise intracellular glutathione levels. When evaluating any liver supplement, check that NAC is present at a minimum of 350mg.

NAC and Alcohol-Related Liver Stress

For people who drink regularly, NAC is particularly important. Alcohol metabolism produces acetaldehyde — a toxic intermediate that depletes glutathione stores in the liver. Without adequate glutathione, the liver cannot neutralise acetaldehyde efficiently, leading to oxidative damage that accumulates over time.

NAC supplementation helps replenish the glutathione pool, enabling the liver to process alcohol's toxic metabolites more effectively. This is why NAC is a non-negotiable ingredient in any liver supplement designed for people who drink.

Which Supplements Include NAC at the Correct Dose?

In our 2026 review of 23 liver supplements, only 9 included NAC at all — and only 5 included it at a dose within the studied therapeutic range. Cloud9 Daily Restore includes NAC at 500mg, which falls within the evidence-based range. 1MD LiverMD includes it at 600mg — the highest dose in our review.