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
A Steady, Dose-Related Pattern
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.
How the Study Worked
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.
Why Alcohol and Breast Tissue May Be Connected
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.
Putting the Risk in Perspective
A percentage like this describes a relative change; the everyday chance for any one woman still depends on many things. 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 questions about your own situation are best explored with a doctor who knows your history.
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.
- If you drink and have a personal or family history of breast cancer, this may be worth raising with your doctor, who can weigh your overall risk and screening options with you.
- Any changes to drinking, medications, or screening are best discussed with your own healthcare provider, especially if you have concerns that are new or persistent.
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