How does alcohol metabolism cause liver damage?

How does alcohol metabolism produce toxic byproducts?

Alcohol is broken down in the liver mainly by alcohol dehydrogenase, which converts ethanol into acetaldehyde. Acetaldehyde is highly reactive and forms damaging adducts with proteins and DNA. A second enzyme, aldehyde dehydrogenase, then turns acetaldehyde into acetate, but this step also generates NADH. Excess NADH shifts the cell’s redox balance, slowing fatty-acid oxidation and promoting fat buildup inside hepatocytes.

Why does continued drinking worsen oxidative stress?

When alcohol intake is heavy or chronic, cytochrome P450 2E1 (CYP2E1) becomes more active and produces reactive oxygen species. These free radicals attack lipids in cell membranes, trigger inflammation, and activate hepatic stellate cells that lay down scar tissue. The combination of acetaldehyde adducts, redox imbalance, and oxidative damage progressively injures liver cells.

What happens if drinking stops versus if it continues?

Short-term abstinence allows the liver to clear fat and reduce inflammation within weeks. Prolonged heavy drinking, however, drives fibrosis and cirrhosis because repeated injury outpaces repair. Once cirrhosis is established, portal hypertension and liver failure can develop even if alcohol is later stopped.

Can genetics change individual risk?

Variants in the genes for alcohol dehydrogenase and aldehyde dehydrogenase alter acetaldehyde clearance rates. People who accumulate acetaldehyde faster experience stronger immediate toxicity, while those with slower clearance may drink more before feeling effects, increasing cumulative liver damage.

Are there medications or interventions that limit this pathway?

Disulfiram blocks aldehyde dehydrogenase, deliberately raising acetaldehyde levels to deter drinking. Emerging compounds that inhibit CYP2E1 or scavenge reactive oxygen species are under study, but none yet replace the primary treatment of sustained alcohol cessation.