Caffeine and Breast Cancer

Health headlines always seem to include a study about caffeine, and whether or caffeine consumption is linked to breast cancer is often raised. While there are many unanswered questions about this, experts are learning that caffeine probably does not increase the likelihood of developing the breast cancer. In fact, it may decrease risk in some women, though more research is certainly needed.

woman holding cup of coffee
 Willie B. Thomas / Getty Images

Reduction in Breast Cancer Risk

Caffeine consumption has been associated with a decreased risk of breast cancer in a few studies, though the results have been inconsistent. Furthermore, the reason for a possible link, as well as the ideal timing and amount of caffeine consumption that could potentially have any effect on breast cancer, are not understood.

An Italian group of researchers who examined 21 studies about this subject noted that they could not find a relationship between caffeine consumption and breast cancer. But when they looked at a small subset of the data, they reported that four cups of coffee per day was associated with a 10% reduction in postmenopausal cancer risk.

A Swedish study echoed this, noting that coffee consumption was associated with a decrease in breast cancer among postmenopausal women. Women who consumed three to four cups of coffee per day had a slightly lower rate of breast cancer than women who consumed two cups of coffee per day or less. And women who consumed five or more cups of coffee per day had an even lower rate of breast cancer.

Researchers who conducted a large multinational trial also suggested that a higher intake of caffeinated coffee could be associated with a lower risk of postmenopausal breast cancer.

Contradictory Results

While the above research in support of caffeine for reduced breast cancer risk is notable, the relationship between caffeine and breast cancer is complicated and unclear. Conflicting conclusions only support how much more there is to know about this topic.

The aforementioned Swedish study that showed a reduction in breast cancer in postmenopausal women who consumed coffee also found that caffeinated tea consumption was associated with an increase in breast cancer, though the reason is uncertain. The multinational trial, which also looked at tea and coffee consumption, did not show any relationship between tea (or decaffeinated coffee) and premenopausal or postmenopausal breast cancer.

While research is ongoing, it's important to remember that some foods and beverages have other components that may, together or alone, impact cancer risk.

Furthermore, a different multicenter trial showed that the potentially beneficial effect of coffee on breast cancer must be caveated when it comes to postmenopausal women using hormone therapy.

Researchers found that postmenopausal women who consumed more than four cups of coffee per day had a 16 percent reduced risk of breast cancer compared to women who consumed less than seven cups of coffee per week. However, women who used postmenopausal hormone therapy and consumed more than four cups of coffee per day had a 22% greater risk of breast cancer than women consuming less than seven cups per week.

Preparation Methods are Also Contradictory

Not only may the question about the effect of coffee on breast cancer risk vary with age, menopausal status, and more, the method by which it's prepared adds another variable. A 2019 study on Chinese women in Hong Kong found that was not associated with the overall risk of breast cancer. When broken down by preparation methods, however, there were significant differences. Women who drank brewed coffee were, on average, 52% less likely to develop breast cancer. In contrast, those who drank instant coffee were 50% more likely to develop the disease.

Just as proper preparation of green tea is essential to obtain the phytonutrients present, the way coffee is prepared could easily affect the nutrients (or carcinogens) present.

There are many factors at play when it comes to the relationship between coffee and breast cancer. Hormone therapy and other risk factors play a far stronger role on the risk of breast cancer than coffee does.

Caffeine As a Breast Cancer Treatment

Caffeine is believed to have antioxidant and anti-inflammatory functions. Antioxidants counteract oxidation—a chemical process that leads to cancer and heart disease. Inflammation exacerbates disease, including cancer. For these reasons, caffeine has been considered as a possible treatment for breast cancer.

Guaraná, a highly caffeinated food, was studied in the laboratory setting. It appeared to stop the growth of breast cancer cells without affecting normal cells. However, this effect has not been seen in humans and the food has not been used as a breast cancer treatment.

Another laboratory experiment evaluated the response of cancer cells to caffeine. The researchers found that cell growth was suppressed in estrogen receptor-positive (ER+) and estrogen receptor-negative (ER-) samples. They also noted that women who consumed high amounts of caffeine and were treated with tamoxifen for breast cancer prevention were less likely to develop the condition. The researchers suggested that caffeine could make women more sensitive to the beneficial effects of the drug.

Because findings in laboratory experiments are not always the same when they are applied to humans, the effects of caffeine on breast cancer cells would have to be replicated in humans before it would be accepted as a treatment for breast cancer. Until more is known, you should not attempt to use caffeine as a strategy for preventing breast cancer.

Green Tea and Breast Cancer Recurrence

Many people who have faced breast cancer are worried about the risk of recurrence, especially upon learning that those who have estrogen receptor positive breast cancer are more likely to have a recurrence after 5 years than in the first 5 years following treatment. While we don't have any solid information on coffee intake and breast cancer recurrence risk, the caffeinated beverage green tea might be an option to consider.

Not only has green tea consumption been associated with a lower risk of developing breast cancer, it's been demonstrated to have anti-cancer activities and it's most powerful link appeared to be in reducing the risk of late recurrence of breast cancer. Since the risk of recurrence of estrogen receptor positive breast cancer remains constant for at least 20 years (meaning that a cancer is just as likely to recur after 10 years as before), this may be good news for those who enjoy green tea.

Practical Habits and Caffeine

There are a number of important issues to consider when it comes to caffeine. While safe for most people, it is not safe for some people who have heart disease, hypertension (high blood pressure), or kidney disease.

Even if you don't have such a contraindication, caffeine can disrupt your sleep, interfere with your concentration, and make you irritable or jumpy. Caffeine may also cause dehydration and worsen symptoms of some gastrointestinal issues.

The effect of caffeine on headaches and migraines can be intense, as caffeine dependence can lead to withdrawal symptoms—which is often associated with severe headaches.

The right amount or maximum amount of caffeine differs for everyone, but it can range from one to five servings of a caffeinated beverage or food per day.

A Word From Verywell

Beyond its potential impact on cancer risk, caffeine may affect breast pain. For instance, some women with fibrocystic breast tissue notice that when they avoid caffeinated products, their breast symptoms improve. This could be related to caffeine's tendency to heighten symptom awareness, which can increase pain sensitivity.

With recent studies highlighting the high risk of late recurrence in estrogen receptor positive breast cancer, the studies on green tea are interesting. Whether this is related to caffeine, or other compounds in green tea, however, may be an important question.

While solid answers are lacking, it may be wise for those who enjoy coffee to choose brewed coffee over instant, at least until more is known.

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