Heavy drinking raises colorectal cancer risk, but quitting reverses it

A 20-year study of nearly 90,000 Americans has found what researchers suspected but hadn't clearly proven: the amount you drink over your lifetime matters significantly for colorectal cancer risk — and quitting appears to undo much of the damage.

The National Cancer Institute tracked 88,092 participants who started cancer-free and followed them for two decades. Over that period, 1,679 developed colorectal cancer. The pattern that emerged was stark: people who averaged 14 or more drinks per week across their lives had a 25% higher risk of colorectal cancer compared to those who drank less than one drink weekly. For rectal cancer specifically, the risk jumped 95%.

What makes this different from earlier research is the focus on lifetime drinking patterns. When scientists looked at how consistently people drank over years and decades, not just their current habits, the numbers became more dramatic. Heavy drinkers throughout adulthood faced a 91% higher colorectal cancer risk than those who drank lightly and steadily.

But here's the part that matters if you're reading this and thinking about your own habits: former drinkers didn't show elevated cancer risk. In fact, people who'd quit drinking had lower rates of adenomas — the noncancerous polyps that can develop into cancer — than current light drinkers. "We were encouraged to see that their risk may return to that of the light drinkers," said Erikka Loftfield, PhD, MPH, a senior researcher at the NCI.

The biological mechanism isn't fully understood yet. Alcohol breaks down into compounds that may damage cells, and it can also alter the bacteria in your gut in ways that increase inflammation. Neither explanation is proven, but both are plausible enough that researchers are investigating further.

The takeaway is less about fear and more about trajectory. Drinking heavily for decades does increase your risk — substantially. But the risk isn't permanent. Your body, it seems, has the capacity to recover.

Study: Association of alcohol intake over the lifetime with colorectal adenoma and colorectal cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial - Cancer, 2023