Last reviewed May 2026. This article is for general information only and does not replace medical advice. If you have specific concerns about coffee consumption and breast health, talk to your healthcare provider, particularly if you have a family history of breast cancer.
Every few years, a headline returns: “Coffee shrinks women’s breasts!” The original 2008 Swedish study that triggered this claim was real, the finding was statistically interesting, and the popular interpretation has been almost entirely wrong. Here’s what the research actually showed, what it didn’t show, and what current evidence says about coffee and breast tissue.
What the 2008 Swedish study actually found
The study by Helena Jernström and colleagues at Lund University, published in the British Journal of Cancer, was titled “Coffee intake and CYP1A2*1F genotype predict breast volume in young women: implications for breast cancer” (Jernström H et al., 2008 – British Journal of Cancer).
The researchers studied 269 women from families with a high genetic risk of breast cancer. They measured each woman’s breast volume, recorded coffee consumption habits, and genotyped them for a specific gene variant (CYP1A2*1F). They were looking for a connection between coffee, breast tissue, and breast cancer risk.
The finding that made headlines: women with a specific gene variant (the CYP1A2*1F C-allele) who drank three or more cups of coffee per day had breasts that measured about 17% smaller in volume than women with the same gene variant who drank less coffee.
What the headlines left out: this difference appeared only in women with the C-allele. Women with the A/A genotype showed no significant breast-size difference based on coffee consumption. In fact, A/A women who drank more coffee had slightly (but not statistically significantly) larger breasts. The “coffee shrinks breasts” finding applied to perhaps half the women in the study, and only in a specific genetic subgroup.
The critical correlation-vs-causation issue
The study measured breast size and coffee intake once. The researchers did not follow women over time to see whether their breasts changed in response to coffee consumption. They observed a statistical association at one moment.
The lead researcher, Helena Jernström, has been explicit in subsequent interviews that the study did not find a causal link between coffee consumption and breast size. The correlation could plausibly reflect:
- A genetic profile that influences both coffee preference AND breast tissue characteristics independently.
- A hormonal interaction between coffee, the CYP1A2 enzyme, and estrogen metabolism (relevant for breast cancer research, not for cosmetic concerns).
- A behavioral pattern in the specific Swedish population studied.
- Random statistical noise that wouldn’t replicate in other populations.
The headline “coffee shrinks your breasts” implies a causal mechanism: drink coffee ? breasts become smaller. The study did not show this. It showed only that, in one snapshot of one population, a specific genetic subgroup of heavy coffee drinkers had measurably smaller breasts than light drinkers in the same genetic subgroup.
What the study was actually about
The Lund researchers were investigating breast cancer risk, not cosmetic breast size. Previous research had shown:
- Heavy coffee consumption is associated with reduced breast cancer risk in some populations.
- Smaller breast size is associated with reduced breast cancer risk (because less breast tissue means fewer cells that could potentially become cancerous).
- The CYP1A2 gene affects how the body metabolizes caffeine and many other compounds, including estrogen.
The researchers were testing whether coffee’s apparent breast-cancer protection might be mediated through effects on breast tissue itself, modulated by genetics. The breast-size finding was a research observation toward this broader question, not a public-health recommendation about cup sizes.
What current research shows about coffee and breast health
- Breast cancer risk: Most large meta-analyses find that moderate coffee consumption is associated with a small reduction in breast cancer risk, particularly for estrogen-receptor-negative breast cancers. The effect is modest and observational.
- Postmenopausal women: Coffee consumption appears to have a slightly protective effect against postmenopausal breast cancer in most studies.
- Tamoxifen interactions: Some research has suggested that coffee may enhance the effectiveness of tamoxifen, a common breast cancer treatment. Discuss with your oncologist if relevant.
- Fibrocystic breast changes: Older research suggested caffeine might worsen fibrocystic breast pain or lumpiness. More recent controlled studies have not consistently confirmed this. For women with significant fibrocystic symptoms, an individual 4-week caffeine reduction trial may be informative.
None of this current research supports the popular interpretation that “coffee shrinks breasts” in a clinically meaningful, cosmetically relevant way. The original 2008 finding has not been usefully replicated in the cosmetic-effect framing.
Practical translation
- Don’t quit coffee out of concern that it’s changing your breast size. The evidence doesn’t support this.
- If you have a strong family history of breast cancer, talk to your healthcare provider about screening and risk factors. Coffee is a small factor at most in a much larger picture.
- If you have fibrocystic breast pain that bothers you, a 4-week caffeine reduction trial is a low-risk experiment that may or may not help.
- For postmenopausal women, moderate coffee consumption appears to be slightly protective against breast cancer based on available evidence.
When to see a doctor
- Any new breast lump, persistent breast pain, or visible breast changes
- Family history of breast cancer in first-degree relatives
- BRCA1/BRCA2 gene mutations (with or without coffee consumption considerations)
- Persistent fibrocystic breast pain interfering with daily life
- Nipple discharge that is bloody, persistent, or from one side only
- Skin changes on the breast (dimpling, redness, scaling)
Regular breast self-exams and clinical screening (mammograms per current guidelines for your age group) are far more important than coffee consumption decisions for breast health.
Frequently asked questions
Does coffee actually shrink breasts?
No. The 2008 Swedish study that triggered this claim found a statistical correlation in one genetic subgroup at one point in time. The lead researcher has been explicit that the study did not show coffee causes breast size changes. Subsequent research has not supported the cosmetic-effect interpretation.
Is coffee linked to breast cancer?
Most large meta-analyses find that moderate coffee consumption is associated with a small reduction in breast cancer risk, particularly for postmenopausal women and certain cancer subtypes. The protective effect is modest and based on observational evidence rather than randomized trials.
Should I cut coffee for fibrocystic breast pain?
Older research suggested caffeine might worsen fibrocystic symptoms. More recent controlled studies have not consistently confirmed this. A 4-week individual caffeine reduction trial is a reasonable, low-risk experiment if you have bothersome fibrocystic symptoms.
What about during pregnancy?
Current ACOG guidance is to keep caffeine under 200 mg per day during pregnancy. See our coffee during pregnancy piece for full details.
Sources
- Jernström H et al. (2008) Coffee intake and CYP1A2*1F genotype predict breast volume in young women: implications for breast cancer. British Journal of Cancer.
- Lukic M et al. (2018) Coffee consumption and the risk of malignant melanoma in the Norwegian Women and Cancer (NOWAC) Study. BMC Cancer.
- American Cancer Society – Breast Cancer Facts and Figures
- Susan G. Komen – Lifestyle Factors and Breast Cancer Risk
This article is for general information only and does not replace personalized medical advice. For breast health concerns, consult your healthcare provider. Regular breast self-exams and recommended clinical screenings are far more important than any single dietary factor.
Discussion 1
I stopped drinking coffee and my breasts augmented in size, so there is a correlation. I stopped drinking coffee because it caused cysts. Too much coffee consumption causes the estrogen levels in women to rise, so yes, it can cause cysts which are caused by over- production of estrogen. I stopped drinking coffee and the cysts went away. Too much coffee is bad for all involved. It also causes hyperthyroid issues in males. Too much of a good thing is bad. Biases are bad. Reporting the truth even when it’s not convenient to one’s agenda, now that’s hard to come by and what a lot of journalists lack these days: integrity.