CATEGORY: WOMEN’S HEALTH
In a study that followed nearly 40,000 women for a median of 25 years, each additional alcoholic drink consumed per day was associated with roughly a 10% higher rate of breast cancer. Because this was an observational study—one that tracks people’s habits and health over time without changing anything—it points to a link, not proof that alcohol directly causes the disease.1
Estrogen Receptor Positive Tumors Showed a 12% Higher Rate
The relationship rose gradually rather than appearing only at heavy-drinking levels: risk climbed step by step with each extra daily drink. The link was clearest for estrogen receptor-positive tumors—breast cancers that grow in response to the hormone estrogen—where each additional daily drink was tied to about a 12% higher rate. For estrogen receptor-negative tumors, which do not depend on estrogen to grow, no clear association appeared. That split is a clue about how alcohol may be involved, not a reassurance that some drinking is risk-free.
39,811 Women Followed a Median of 25 Years
The findings come from the Women’s Health Study, a large United States cohort of female health professionals. At the start, participants reported how much alcohol they typically drank. Researchers then followed 39,811 women for a median of 25 years—meaning half were tracked even longer—and recorded 2,830 new breast cancer diagnoses, including 237 deaths from the disease, confirmed through medical records. Comparing cancer rates across different reported drinking levels, while accounting for other differences between the women, is how the researchers arrived at the roughly 10%-per-drink figure. Because the outcome unfolded over decades, that long follow-up is central to the result, not a side detail.
Estrogen and Acetaldehyde as the Leading Proposed Explanations
Researchers have long suspected estrogen plays a part. Drinking alcohol can raise levels of estrogen—a hormone that can encourage certain breast cells to divide—which may help explain why the association in this study was strongest for estrogen-sensitive tumors. Breaking down alcohol in the body also produces acetaldehyde, a byproduct that can damage DNA, the instruction manual inside cells. The study itself measured drinking and cancer rather than this underlying biology, so these mechanisms remain the leading explanation rather than something the study proved directly.
About 4% of These Cancers Attributed to Drinking
A percentage like this describes a relative change; the everyday chance for any one woman still depends on many things. In a model of 100,000 women followed for 10 years, the researchers projected about 279 more breast cancer cases if all drank more than one drink a day.1 The researchers estimated that only about 4% of the breast cancers in this group could be attributed to drinking more than roughly one drink a month—a reminder that most cases arose from other causes entirely. And because drinking habits often travel alongside other lifestyle and health factors, an observational study cannot fully untangle alcohol from everything else in a person’s life. Breast cancer risk is shaped by genetics, family history, reproductive history, body weight, and more, so alcohol is only one thread among many.
106 Pooled Studies Showed Rates Rising With Drinking Level
This pattern shows up well beyond this one study. A 2023 review pooling 106 long-term studies found breast cancer rates about 5% higher in women drinking under roughly one drink a day than in non-drinkers, about 12% higher at one to two drinks, and about 23% higher at roughly two to three.2 Those were observational studies too, so they describe the same link rather than proving alcohol causes the disease.
Key Takeaways
- In this 25-year study of nearly 40,000 women, each additional daily alcoholic drink was linked to about a 10% higher rate of breast cancer, with the clearest signal for estrogen-sensitive tumors.
- The study shows an association, not proof of cause, and most breast cancers in the group were not attributed to alcohol.
- Drinking habits were reported by questionnaire and the women were followed for about 25 years, so the study tracks patterns over time rather than any single episode of drinking.
References
- Mostofsky E, Lee I-M, Buring JE, Mukamal KJ. Impact of Alcohol Consumption on Breast Cancer Incidence and Mortality: The Women’s Health Study. Journal of Women’s Health. 2024;33(6):705–714. link
- Jun S, Park H, Kim UJ, et al. Cancer risk based on alcohol consumption levels: a comprehensive systematic review and meta-analysis. Epidemiology and Health. 2023;45:e2023092. link.