The short answer is yes. Caffeine can affect breast tissue. However, caffeine doesn’t cause breast cancer.

The details are complex and can be confusing. The bottom line is that the connection between caffeine and breast tissue shouldn’t necessarily change your coffee or tea drinking habits.

Here’s what we know, in brief:

  • Caffeine isn’t a risk factor for breast cancer.
  • There may be a small association between breast tissue density and caffeine. This doesn’t mean a cause.
  • Many studies have concluded that dense breast tissue is a strong risk factor for breast cancer.

In this article, we’ll delve deeper into caffeine, breast density, and the connection between breast density and breast cancer.

There are very few studies of caffeine and breast tissue density, and results are mixed.

A 2000 study found no association of caffeine to breast density. Similarly, a 2019 study of adolescents who consumed caffeine found no association with breast density in premenopausal women.

However, a 2018 study of 4,130 healthy women found a small association between caffeine intake and breast density. The study results differed, depending on whether the women were premenopausal or postmenopausal:

  • Postmenopausal women with a higher caffeine or decaffeinated coffee intake had a lower percentage of breast tissue density.
  • Premenopausal women with higher coffee intake had a higher percentage of breast density.
  • Postmenopausal women on hormone therapy who had higher coffee and caffeine intake had a lower percentage of breast density. Because hormone therapy tends to be associated with increased breast density in general, the study suggests that caffeine intake might reduce this effect.

What’s in caffeine that might affect breast tissue?

The connection between caffeine and breast tissue density isn’t fully understood.

It’s suggested that the many biologically active compounds (phytochemicals) in caffeine may stimulate enzymes involved with estrogen metabolism and decreasing inflammation. These phytochemicals may also inhibit gene transcription by adding methyl groups to the DNA molecules.

In animal tests, coffee compounds suppressed the formation of breast tumors, as reported in a 2012 study of caffeine and breast cancer. A 2015 study found that caffeine and caffeic acid had anticancer properties in relation to estrogen receptor genes.

Having dense breasts means that you have more fibrous or glandular tissue and not as much fatty tissue in your breasts. Almost half of American women have breasts that are dense. It’s normal.

There are four classes of breast density as defined by the American College of Radiology:

  • (A) almost entirely fatty breast tissue
  • (B) scattered areas of dense tissue
  • (C) varying (heterogeneously) dense breast tissue
  • (D) extremely dense breast tissue

About 40 percent of women fall into category C and about 10 percent in category D.

Dense breasts are especially common in younger women and women with smaller breasts. Nearly three-quarters of women in their 30s have dense breast tissue, compared to one-quarter of women in their 70s.

But anyone, no matter what breast size or age, can have dense breasts.

How do you know if you have dense breast tissue?

You can’t feel breast density, and it’s not related to breast firmness. It can’t be detected with a physical exam. The only way to see breast tissue density is on a mammogram.

Healthline

Breast tissue density is well established as a high risk for breast cancer. The risk is higher for the 10 percent of women who have extremely dense breasts.

However, having dense breasts doesn’t necessarily mean you’ll develop breast cancer. The concern with dense breasts is that even a 3-D mammogram (called a digital breast tomosynthesis) can miss a developing cancer in dense breast tissue.

It’s estimated that up to 50 percent of breast cancers can’t be seen on a mammogram in women who have dense breasts.

Consider yearly ultrasound tests

If your mammogram shows that you have dense breast tissue, especially if more than half your breast tissue is dense, discuss additional yearly ultrasound testing with your doctor.

Breast ultrasound exams detect an additional 2 to 4 tumors per 1,000 women screened by mammograms.

Consider yearly MRI screenings

For women with a high breast cancer risk from dense breast tissue or other risk factors, discuss with your doctor about having a yearly MRI screening. Breast MRI finds an average of 10 additional cancers per 1,000 women, even after a mammogram and ultrasound screening.

If you don’t have a mammogram, you can’t know if you have an increased risk of breast cancer from having dense breasts, a spokesperson for the National Cancer Institute (NCI) emphasizes. Women should discuss family history and other risk factors with their healthcare provider to determine the mammogram schedule most appropriate for them.

Whether to have yearly supplemental breast screening if you have dense breasts is an individual decision. Discuss the pros and cons with a doctor.

Supplemental screening increases the early detection of breast cancer in dense breasts. And catching a breast cancer tumor early has a better outcome.

The U.S. Preventive Services Task Force advised in 2016 that the current evidence wasn’t sufficient “to assess the balance of benefits and harms” of additional screening for women with dense breasts. Potential harms include:

  • possible false positives
  • biopsy infection
  • unnecessary treatment
  • psychological burden

The website of densebreast-info.org reviews the pros and cons of screening.

You can also find more screening information in the patient guide to screening options on the website of the nonprofit organization areyoudense.org.

“You can’t change your breast density, but you can monitor your breasts with a yearly 3-D mammogram and an ultrasound,” Joe Cappello, executive director of Are You Dense, Inc., told Healthline.

A 2017 article on breast cancer risk that analyzed 18,437 women with breast cancer suggested that reductions in breast tissue density could substantially reduce the numbers of breast cancer. But this would require new research developments.

The researchers propose that lowering breast density could hypothetically be achieved with the preventive use of tamoxifen citrate for those women in highest risk categories.

Tamoxifen is an anti-estrogen drug. A randomized clinical trial reported in 2004 found that tamoxifen treatment reduced breast density, especially in women younger than 45.

“Maintain a healthy weight and get regular exercise,” an NCI spokesperson recommends. “These are two things you can do to reduce your breast cancer risk, although you can’t change your breast density or your genetic susceptibility to breast cancer.”

Years of research on caffeine and breast cancer have found that drinking coffee or other caffeinated beverages doesn’t increase your risk of breast cancer.

This is the case for both younger and older women. But for reasons not fully explained, higher caffeine intake seems to lower the risk of breast cancer for postmenopausal women.

A 2015 study of 1,090 women in Sweden with breast cancer found that coffee consumption wasn’t associated with overall disease prognosis. But women with estrogen-receptor-positive type tumors who drank two or more cups of coffee a day had a 49 percent decrease in cancer recurrence, compared to similar women who drank less coffee.

The authors of the 2015 study suggest that caffeine and caffeic acid have anticancer properties that reduce breast cancer growth by making estrogen-receptor tumors more sensitive to tamoxifen.

Ongoing research is looking at what properties of caffeine might affect breast cancer risk and breast cancer progression.

Caffeine doesn’t cause breast cancer, according to multiple research studies over decades.

There’s limited evidence of a small association between caffeine and breast density, which differs for premenopausal and postmenopausal women.

Having dense breast tissue is a strong risk factor for breast cancer. Women with dense breast tissue should have a yearly mammogram and consider having supplemental screening tests. Detecting breast cancer early leads to a better outcome.

Every woman is different, and is affected differently by the same cancer risk. The good news is that there’s now an increased awareness of breast cancer risks and breast density.

Many online resources can answer questions and put you in touch with other women coping with breast cancer risk or breast cancer, including areyoudense.org and densebreast-info.org. The National Cancer Institute has breast cancer information and a hotline and live chat to answer questions.