By Craig Weatherby
Can coffee help curb the risk of new or recurrent breast cancers?
The answer may depend on the kind of cancer and a person's “genotype”, but the general indications are positive.
Breast cancers are divided into two major classes, depending on whether they have estrogen receptors (ER-positive) or lack them (ER-negative).
ER-negative tumors have historically had a poorer prognosis and fewer prevention and treatment strategies, compared to ER-positive tumors, although some treatments show promise.
About one-third of all breast cancers involve ER-negative tumors, while some 15 percent are triple-negative cancers, whose cells lack receptors for any of the three potentially cancer-fueling hormones: estrogen (ER), progesterone (PR), and human epidermal growth factor.
Coincidentally, researchers recently reported finding links between higher vitamin D or omega-3 blood levels and lower risk of tough, triple-negative tumors … see “Vitamin D Lack Linked to Toughest Breast Tumors” and “Omega-3s Target Toughest Breast Tumor”.)
Coffee's anti-cancer potential seen in lab and population studies
Several studies have suggested that coffee can curb certain estrogen-dependent breast cancers.
About tamoxifen
So-called “estrogen-dependent” cancers are the most common kind.
They need that female hormone to grow and can be curbed by “anti-estrogen” drugs, which reduce the risk of new tumors by blocking the estrogen receptors on human cells.
Tamoxifen – originally derived from the bark of the Pacific yew tree – is the synthetic anti-estrogen drug most commonly taken by patients with estrogen-dependent breast cancer.
Tamoxifen is prescribed in various scenarios and for various purposes:
  • Treat breast cancer that's spread to other parts of the body.
  • Treat early breast cancer in women who've undergone surgery, radiation, and/or chemotherapy.
  • Reduce the risk of breast cancer in women at high risk due to their age, medical history, and family history.
  • Reduce the risk of more-serious tumors in women who've had ductal carcinoma in situ (DCIS) and were treated with surgery and radiation.
Taking tamoxifen for five years can cut a woman's risk of developing breast cancer nearly in half.
Breast cancer returns in about 46 percent of women who stop taking it early, compared to 40 percent who complete the five-year course.
Many women stop taking it early due to side effects. The drug raises risks for endometrial cancer, deep venous thrombosis, pulmonary embolism, painful sexual intercourse and cataracts.
For example, scientists from Sweden's Lund University conducted a “case-control” study among 458 women with specific variants (genotype) of a gene that commands production of an enzyme called CYP1A2 … which is involved in metabolizing both estrogen and coffee (Bågeman E et al. 2008).
Intriguingly, diagnosis of breast cancer occurred an average of seven years later among the women who reported moderate to high coffee consumption, compared with the women who drank less coffee or none.
As they said,” These findings raise the hypothesis that coffee slows the growth of ER-positive [estrogen-dependent] tumors in patients with [certain CYP1A2 gene profiles] and may have implications for breast cancer [prevention] if confirmed,” (Bågeman E et al. 2008)
Two years ago, researchers from Sweden's Karolinska Institute conducted another case-control study, which linked drinking five or more cups of regular or decaf coffee daily to reduced risk of postmenopausal breast cancers that are not dependent on estrogen (Li J et al. 2011).
(For more on that study, see “Does Coffee Curb Breast Cancer?”.)
Just last month, Canadian researchers reported encouraging results from their case-control study in 6,089 women, about half of whom were breast cancer patients (Lowcock EC et al. 2013).
The Canadian team's analysis linked high coffee consumption to a reduced risk of estrogen-dependent and postmenopausal breast cancers, regardless of the participants' personal CYP1A2 genotypes.
As in the Karolinska Institute study, “high coffee consumption” was defined as five or more cups of regular or decaf a day.
Needless to say, drinking five cups of regular coffee a day would deliver more caffeine than most people can tolerate.
However, decaf may work just as well, since the Canadians found no link between higher caffeine intake and reduced breast-cancer risk.
Now, a new study from Lund University suggests that coffee may boost tamoxifen's ability to slash the recurrence of estrogen-dependent breast cancers.
Swedish study links coffee to reduced risk of cancer recurrence
Scientists from Sweden's Lund University followed 634 breast cancer patients – 310 of whom were taking tamoxifen – for an average of five years.
Compared with patients who took tamoxifen and drank one cup of coffee daily or less, breast cancer was only half as likely to return in the tamoxifen-taking patients who drank two or more cups of coffee daily.
As the researchers wrote, “Moderate to high coffee consumption was associated with significantly decreased risk … If [the findings are] confirmed, new recommendations regarding coffee consumption during tamoxifen treatment may be warranted.” (Simonsson M et al. 2013)
This finding lends strong – albeit inconclusive – support to the indications seen in lab studies.
The connection between estrogen, coffee, and the CYP1A2 enzyme may be a clue, but it's still not clear exactly how coffee would enhance the efficacy of tamoxifen.
As lead author Maria Simonsson said, “One theory we are working with is that coffee ‘activates' tamoxifen and makes it more efficient.” (LU 2013)
And although the April, 2013 Canadian study did not find any link higher caffeine intake and reduced cancer risk, caffeine has previously been shown to hamper the growth of cancer cells.  
  • Bågeman E, Ingvar C, Rose C, Jernström H. Coffee consumption and CYP1A2*1F genotype modify age at breast cancer diagnosis and estrogen receptor status. Cancer Epidemiol Biomarkers Prev. 2008 Apr;17(4):895-901. doi: 10.1158/1055-9965.EPI-07-0555.
  • Klug TL, Bågeman E, Ingvar C, Rose C, Jernström H. Moderate coffee and alcohol consumption improves the estrogen metabolite profile in adjuvant treated breast cancer patients: a pilot study comparing pre- and post-operative levels. Mol Genet Metab. 2006 Dec;89(4):381-9. Epub 2006 Sep 15.
  • Kotsopoulos J, Ghadirian P, El-Sohemy A, Lynch HT, Snyder C, Daly M, Domchek S, Randall S, Karlan B, Zhang P, Zhang S, Sun P, Narod SA. The CYP1A2 genotype modifies the association between coffee consumption and breast cancer risk among BRCA1 mutation carriers. Cancer Epidemiol Biomarkers Prev. 2007 May;16(5):912-6.
  • Li J, Seibold P, Chang-Claude J, Flesch-Janys D, Liu J, Czene K, Humphreys K, Hall P. Coffee consumption modifies risk of estrogen-receptor negative breast cancer. Breast Cancer Res. 2011 May 14;13(3):R49. doi: 10.1186/bcr2879.
  • Lowcock EC, Cotterchio M, Anderson LN, Boucher BA, El-Sohemy A. High Coffee Intake, but Not Caffeine, is Associated with Reduced Estrogen Receptor Negative and Postmenopausal Breast Cancer Risk with No Effect Modification by CYP1A2 Genotype. Nutr Cancer. 2013 Apr;65(3):398-409. doi: 10.1080/01635581.2013.768348.
  • Lund University (LU). Coffee may help prevent breast cancer returning, study finds. April 24, 2013. Accessed at
  • Simonsson M, Söderlind V, Henningson M, Hjertberg M, Rose C, Ingvar C, Jernström H. Coffee prevents early events in tamoxifen-treated breast cancer patients and modulates hormone receptor status. Cancer Causes Control. 2013 May;24(5):929-40. doi: 10.1007/s10552-013-0169-1. Epub 2013 Feb 15.