Studies have not established the effect of black tea on breast cancer
Black tea is made by adding hot water to the cured leaves of the Camellia sinensis plant. Green tea leaves are unoxidized, whereas black tea leaves have been allowed to oxidize. "Tea" refers to black tea for purposes of this web page. Green tea and herbal teas such as yerba maté and chamomile, mint, sage, and Essiac™ tea are covered in other web pages. Tea has been shown to have antioxidant and anti-inflammatory properties. Tea may improve glucose metabolism and has been shown to support weight loss. Tea consumption has been found to be associated with increased bone mineral density and may help prevent osteoporotic fractures in older women. Tea contains theaflavins, catechins, quercetin and other polyphenols that are thought to be responsible for its anti-cancer activities. Tea consumption has been found to be associated with reduced risks of squamous cell carcinoma of the skin, head and neck cancers, and adult leukemia, as well as gastric, endometrial, colorectal, and prostate cancer. On the other hand, maternal tea drinking during pregnancy has been found to be associated with increased risk of childhood central nervous system tumors.Breast cancer-related effects of drinking black tea
Laboratory studies have found that tea extracts or tea polyphenols suppress breast cancer. For example, tea theaflavins have been shown to inhibit proliferation of MCF-7 human estrogen receptor positive (ER+) breast cancer cells, as well as ER- cells, and HER2/neu-overexpressing cells. Tea extract consisting predominantly of theaflavins has been shown to delay mammary tumor development, reduce tumor burden and prolong survival in Tag mice, which develop estrogen independent (ER-) mammary tumors.
The majority of epidemiological studies have found no association or a modest negative association between tea intake and risk of breast cancer. Stronger associations have been found for subsets of women and breast cancer types:
- Drinking black tea has been found to be associated with a protective effect for those with lobular breast cancer.
- Women under 50 who consumed three or more cups of tea per day had a 37% lower risk of breast cancer than women under 50 reporting no tea consumption in one study. This inverse association was found for in situ and invasive breast cancer, and for ductal as well as lobular breast cancer.
- An inverse relationship between caffeine intake and breast cancer was found among postmenopausal women in one large study.
- A large Swedish prospective study found that black tea may be positively associated with risk of ER+/PR+ breast cancer.
- A meta-analysis of five cohort studies found a small increase in breast cancer risk associated with black tea consumption; the authors concluded that the data suggested a possible late-stage, promotional effect of black tea on breast carcinogenesis.
- A study of the relationship between tea intake and circulating steroid hormone levels found that while higher green tea consumption was associated with lower estrone, estradiol and androstenedione levels, higher black tea consumption was associated with higher plasma levels of these hormones. The potentially differing effects of black and green tea on circulating estrogen levels could influence the impact of tea consumption on breast cancer risk.
- A large Netherlands prospective study found that breast cancer incidence was increased among consumers of five or more cups of tea per day. However, the association was not strictly statistically significant ( RR = 1.3 (95% confidence interval = 0.9-2.0)) and no dose-response relationship was observed.
- A study of the relationship between diet and male breast cancer found that tea drinking was associated with higher risk. However, a puzzling finding in the same study that citrus fruit consumption was also associated with an increase in male breast cancer risk limits the usefulness of the finding with respect to tea (i.e., the findings need to be replicated and explained. Our guess would be that folate metabolism may be involved).
Studies comparing black tea to green tea consumption have consistently found that green tea is associated with lower risk of breast cancer than black tea. One possible explanation is that green tea polyphenols include mostly catechins (up to 40% of dry weight); whereas black tea polyphenols include more than 20% thearubigins (formed during oxidation of the tea leaves), up to 10% catechins, and approximately 5% theaflavins. Catechins have been found to possess more powerful anti-cancer properties than thearubigins. As mentioned above, green tea also appears to have more favorable impact on circulating estrogens than black tea. Given that green tea has more consistent anti-cancer properties than black tea and that black tea apparently can promote breast cancer under some circumstances (although these circumstances are not well understood), we conclude that green tea is preferable for those with breast cancer, survivors and those at high risk for breast cancer.
Additional comments
Drinking very hot black tea (or very hot tea of any type) should be avoided. Rates of esophageal cancer are high in areas of the world where tea normally is consumed at high temperatures. In one study, the risk of esophageal cancer was found to be eight times higher for those who regularly drank very hot tea compared to those who drank warm or lukewarm tea. Note that it is the hot temperature that contributes to esophageal cancer, not the compounds found in tea.
Tea consumption decreases the bioavailability of folic acid in the diet by reducing the level of intestinal absorption and interfering with the folate pathway. This folate cycle inhibition is thought to be one mechanism by which green tea protects against breast cancer. Similarly, tea inhibits iron absorption and high levels of iron in benign breast tissue has been found to be associated with increased risk of subsequent breast cancer. For those who require additional folate or iron, however, vitamin pills or other supplements containing folate or iron should not be taken with tea.
Prepared tea contains less than half the caffeine of the same amount of drip coffee. However, high caffeine intake may increase the risk of benign breast disease, particularly atypical hyperplasia, which is associated with increased breast cancer risk. Those sensitive to caffeine or with benign breast disease should take steps to limit their caffeine intake.
People with a history of kidney stones should avoid drinking black tea, since such consumption has been shown to increase the risk of kidney stone formation due to tea's oxalate content.
Selected studies
Coffee and black tea consumption and risk of breast cancer by estrogen and progesterone receptor status in a Swedish cohort Cancer Causes and Control, December 2009The present prospective study was designed to investigate the associations of caffeinated coffee and black tea consumption with risk of breast cancer overall and by hormone receptor status. The study included 61,433 women in the Swedish Mammography Cohort who were cancer free during the baseline enrollment period of 1987 to 1990. Coffee and tea intake was determined using a food-frequency questionnaire administered both at baseline and in 1997. Swedish cancer registers were accessed to obtain information concerning the incidence and nature of newly diagnosed invasive breast cancers in the study cohort. During an average follow-up period of 17.4 years (through year-end 2007), 2,952 incident cases of invasive breast cancer were found. Coffee consumption was found not to be associated with overall risk of breast cancer (multivariate relative risk (RR) for at least four cups per day compared to less than one cup per day = 1.02; 95% confidence interval (CI) = 0.87 - 1.20). Nor was any association found between coffee consumption and breast cancer subtype defined by estrogen receptor (ER) and progesterone receptor (PR) status. On the other hand, black tea intake was found to be significantly positively associated with risk of breast cancer overall and ER+/PR+ tumors in particular. The multivariate RRs comparing at least two cups of black tea per day with no consumption were 1.22 (95% CI = 1.05 - 1.42) for breast cancer overall and 1.36 (95% CI = 1.09 - 1.69) for ER+/PR+ breast cancer. The authors conclude that the study findings do not support a role of coffee consumption in the development of breast cancer. However, the results suggest that black tea may be positively associated with risk of ER+/PR+ breast cancer.
Coffee and tea intake and risk of breast cancer Breast Cancer Research and Treatment, October 2009
The current prospective study was designed to investigate the associations between coffee and tea consumption and the risk of breast cancer. The associations were assessed among women in the EPIC-NL cohort in the Netherlands, which has 27,323 participants. A validated food frequency questionnaire was used to estimate exposure to coffee and tea. Direct linkage with the Netherlands Cancer Registry was utilized to obtain cancer diagnosis-related data. During a 9.6-year follow-up period, 681 invasive primary breast cancers were diagnosed. Before adjustment for breast cancer risk factors and lifestyle, coffee intake was found to increase the risk of breast cancer by more than double as compared to non-coffee drinkers (HR = 2.25, 95% CI = 1.30-3.90). However, this association did not hold after multivariate adjustment, which resulted in HR = 1.17, 95% CI = 0.65-2.12. In fact, after adjustment for breast cancer risk factors and lifestyle, no associations were found between intake of coffee or tea and risk of breast cancer across all levels of intake. The results also were also not affected by body mass index. The authors conclude that coffee and tea consumption does not seem to be related to the risk of breast cancer in women.
Tea consumption and risk of breast cancer Cancer Epidemiology Biomarkers & Prevention, January 2009
The present large U.S. population study was designed to examine the association between regular tea consumption and breast cancer risk. The study included 5,082 women with breast cancer aged 20 - 74 years from cancer registries in Wisconsin, Massachusetts, and New Hampshire, as well as 4,501 age-matched controls from lists of licensed drivers and Medicare beneficiaries. Study participants completed a structured telephone interview to elicit information on usual tea consumption five years prior to the interview and other breast cancer risk factors. Logistic regression was used to calculate covariate-adjusted odds ratios and 95% confidence intervals. Tea consumption was found not to be associated with breast cancer risk overall (P for trend = 0.18). However, when analyzed by age, women under 50 who consumed three or more cups of tea per day were found to have a 37% lower breast cancer risk compared to women under 50 reporting no tea consumption (age and study site-adjusted odds ratios, 0.63; 95% confidence interval, 0.44-0.89; P = 0.01) with a significant test for trend (P = 0.01). The inverse association noted among younger women was found for both in situ and invasive breast cancer, and for ductal as well as lobular breast cancer. These results were not altered after adjusting for established risk factors. The authors conclude that there was evidence in the study to support a potential beneficial impact on breast cancer risk associated with moderate levels of tea consumption (at least three cups per day) among younger women. Further research is needed to confirm this association.
Caffeine consumption and the risk of breast cancer in a large prospective cohort of women Archives of Internal Medicine, October 2008
In this prospective study, the association between caffeine consumption and breast cancer risk in 38,432 women 45 years or older and enrolled in a completed cancer prevention trial was studied. The women were cancer free at baseline (1992-1995), when detailed dietary information was collected from them. There were 1,188 invasive breast cancer cases during a mean follow-up period of ten years. Consumption of caffeine, caffeinated beverages and caffeinated foods was found not to be significantly associated with overall risk of breast cancer. Multivariate relative risks (RRs) of breast cancer were found to be 1.02 (95% confidence interval [CI]: 0.84-1.22) for caffeine (top vs. bottom quintile), 1.08 (CI: 0.89-1.30) for coffee (greater or equal to four cups daily vs. almost never), and 1.03 (CI: 0.85-1.25) for tea (greater than or equal to two 2 cups daily vs. almost never). However, for women with benign breast disease, a borderline significant positive association with breast cancer risk was found for the highest quintile of caffeine consumption (RR = 1.32; CI: 0.99-1.76). In addition, for the highest coffee consumption (greater than or equal to four cups per day), tests for interaction were marginally significant (1.35; CI: 1.01-1.80). Caffeine consumption was also found to be significantly positively associated with the risk of estrogen and progesterone receptor negative (ER-,PR-) breast cancer (1.68; CI: 1.01-2.81) and with breast tumors larger than two cm (1.79; 1.18-2.72). While the data showed no overall association between caffeine consumption and breast cancer risk, they indicate the possibility of increased risk in women with benign breast disease for tumors that are estrogen and progesterone receptor negative or larger than 2 cm.
Coffee, tea, caffeine and risk of breast cancer: a 22-year follow-up International Journal of Cancer, May 2008
The relationship between coffee, tea and caffeine consumption and the risk of breast cancer remains unsettled. In the current prospective study, data from 85,987 female participants in the Nurses' Health Study was used to evaluate whether high intake of coffee and caffeine is associated with increased risk of breast cancer. Levels of intake of coffee, tea and caffeine were assessed in 1980, 1984, 1986, 1990, 1994, and 1998 and the follow-up period extended through 2002. There were 5,272 new cases of breast cancer. The following multivariate relative risks (RRs) of breast cancer were found for caffeinated coffee consumption: 1.0 for fewer than one cup per month (reference category), 1.01 (95% confidence interval: 0.92-1.12) for one cup per month to 4.9 per week, 0.92 (0.84-1.01) for 5 cups per week to 1.9 cups per day, 0.93 (0.85-1.02) for 2 to 3.9 cups per day, 0.92 (0.82-1.03) for greater than or equal to 4 cups per day (p for trend = 0.14). None of these relationships were statistically significant. Intakes of tea, decaffeinated coffee, and caffeine also were not found to be significantly correlated with risk of breast cancer. However, a significant inverse relationship between caffeine intake and breast cancer was found among postmenopausal women; for the highest quintile of intake compared to the lowest quintile RR = 0.88 (95% CI = 0.79-0.97, p for trend = 0.03). The authors conclude that the study uncovered no substantial association between coffee and tea consumption and the risk of breast cancer in the overall cohort. However, a weak inverse association between caffeine-containing beverages and the risk of postmenopausal breast cancer was found.
Green tea, black tea and breast cancer risk: a meta-analysis of epidemiological studies Carcinogenesis, July 2006
The present meta-analysis was designed to examine the associations between green tea and black tea drinking and breast cancer risk. The analysis included 13 population studies in eight countries that provided data on intake of green tea, black tea, or both in relation to risk of breast cancer. Summary odds ratios (ORs) for highest versus lowest or non-tea consumption level were estimated based on fixed and random effects models. Q statistics were used to examine heterogeneity between studies. With respect to green tea, the combined results from the four relevant studies indicated a reduced risk of breast cancer for the highest versus non/lowest intake (OR = 0.78, 95% CI = 0.61–0.98). However, conflicting results were observed for black tea in case-control compared to cohort studies. The combined results from the eight relevant case-control studies found a small reduction in breast cancer risk associated with black tea intake (OR = 0.91, 95% CI = 0.84–0.98). This inverse association was found to be stronger in hospital-based (OR = 0.77, 95% CI = 0.50–1.19) than population-based case–control studies (OR = 0.94, 95% CI = 0.81–1.09). However, five cohort studies showed a small increase in breast cancer risk associated with black tea consumption (OR = 1.15, 95% CI = 1.02–1.31). The authors conclude that green tea consumption is associated with a lower risk of breast cancer. The available data also suggest a possible late-stage, promotional effect of black tea on breast carcinogenesis.
Consumption of antioxidant-rich beverages and risk for breast cancer in French women Annals of Epidemiology, July 2006
The current prospective study was designed to evaluate the associations between antioxidant-rich beverages and the risk of breast cancer. Study participants included 4,396 women without a history of cancer who already were enrolled in the French Supplémentation en Vitamines et Minéraux Antioxydants Study. Beverage intake was assessed by means of three nonconsecutive 24-hour consumption recalls. Incident breast cancer cases were identified through clinical examinations performed every two years (including, for example, a screening mammogram) in addition to a monthly health questionnaire. During an average follow-up period of 6.6 years, 95 breast cancers were newly diagnosed. In a multivariate model, an inverse association between herbal tea consumption and risk of breast cancer was found. For those consuming 1 to 149 mL/day of herbal teas compared to no consumption, relative risk (RR) = 0.93, 95% confidence interval (CI) = 0.48-1.80, and for those consuming at least 150 mL/day, RR = 0.43; 95% CI = 0.20-0.94, p for trend = 0.04. Intakes of coffee, tea, fruit juices, and wine were not associated with risk of breast cancer. The authors conclude that consumption of herbal tea may have a role in the prevention of breast cancer.
Consumption of coffee, but not black tea, is associated with decreased risk of premenopausal breast cancer Journal of Nutrition, January 2006
The current hospital-based, case-control study was designed to assess the role of coffee (including decaffeinated coffee) and black tea on the risk of breast cancer. Participants included 1,932 breast cancer cases and 1,895 hospital controls with noncancer conditions. All of the women completed a detailed questionnaire. For premenopausal women, coffee consumption was found to be associated with linear declines in the risk of breast cancer (P for trend = 0.03). Those who drank at least four cups per day experienced a 40% risk reduction (odds ratio = 0.62, 95% CI: 0.39-0.98). No clear relationships between consuming black tea or decaffeinated coffee and breast cancer risk were found among premenopausal women. However, drinking black tea was associated with a protective effect for those with lobular breast cancer. For postmenopausal women, no associations were found between consumption of coffee, tea, or decaffeinated coffee and breast cancer risk. Results did not differ for those with lobular breast cancer among the postmenopausal women. The authors conclude that coffee intake has a protective effect on premenopausal, but not postmenopausal breast cancer risk.
Tea and circulating estrogen levels in postmenopausal Chinese women in Singapore Carcinogenesis, January 2005
The current Singapore cross-sectional study was designed to examine the associations between tea intake and plasma estrogen and androstenedione levels in healthy postmenopausal ethnic Chinese women. The role of tea drinking in the development of breast cancer is controversial. The authors previously found that tea consumption is associated with reduced breast cancer risk, however this result was largely confined to intake of green tea. Since black tea and green tea have comparable levels of total tea polyphenols possessing antioxidative activities, the reasons for the differing effects of green tea and black tea on breast cancer protection are not clear. There exists some limited evidence that green tea might have downregulatory effects on circulating sex-steroid hormones, while black tea might have upregulatory effects. The present study was designed to examine the circulating sex-steroid hormones in relation to tea consumption. The study included 130 postmenopausal women, of whom 84 were non- or sporadic (fewer than once per week) tea drinkers, 27 were regular (weekly/daily) green tea drinkers and 19 were regular black tea drinkers. Compared to plasma estrone levels in non- or sporadic tea drinkers (29.5 pg/ml), the estrone levels were found to be 13% lower in regular green tea drinkers (25.8 pg/ml) and 19% higher in regular black tea drinkers (35.0 pg/ml). These estrone level differences were statistically significant even after adjusting for age, body mass index, intake of soy, and other covariates (P = 0.03). Similar patterns were found between tea intake and levels of estradiol (P = 0.08) and androstenedione (P = 0.14). The authors conclude that larger studies are needed to confirm these results and to better understand the potentially differing effect of black and green tea on circulating estrogen levels and ultimately on the risk of breast cancer.
Dietary flavonols and flavonol-rich foods intake and the risk of breast cancer International Journal of Cancer, December 2004
Food frequency questionnaires were given to 90,630 women in the Nurses Health Study II in 1991 and 1995 to evaluate the association of flavonol intake with breast cancer risk in premenopausal women who were between 26 and 46 years at baseline in 1991. During eight years of follow-up, there were 710 cases of invasive breast cancer. There were no associations seen between consumption of individual flavonols such as kaempferol, quercetin or myricetin and breast cancer risk. The multivariate RR, comparing highest to lowest quintiles of cumulative average flavonol intake, was 0.94 for sum of flavonol-rich foods. Among the major food sources of flavonols, the authors found a significant inverse association of breast cancer with intake of beans and lentils but not with tea, onions, apples, string beans, broccoli, green pepper or blueberries.
Black tea polyphenol theaflavins inhibit aromatase activity and attenuate tamoxifen resistance in HER2/neu-transfected human breast cancer cells through tyrosine kinase suppression European Journal of Cancer, September 2004
The present study was designed to investigate the inhibitory effects of black tea polyphenols on aromatase activities. The aromatase enzyme plays a role in regulating the availability of estrogen by converting androstenedione to estrone, which in turn may support the growth of hormone-dependent breast cancer. It was found that the black tea polyphenols TF-1, TF-2 and TF-3 significantly inhibited both rat ovarian and human placental aromatase activities. Furthermore, these black tea polyphenols were also found to inhibit the proliferation induced by 100 nM dehydroepiandrosterone (DHEA) in human MCF-7 breast cancer cells in an in vivo model. Of note was the finding that, unlike the selective estrogen receptor modulator tamoxifen, black tea polyphenols were found to have antiproliferative effects in breast cancer cells with hormonal resistance. Black tea polyphenols also suppressed the basal receptor tyrosine phosphorylation in HER2/neu-overexpressing MCF-7 cells. The authors conclude that the use of black tea polyphenols might be beneficial in the chemoprevention of hormone-dependent breast cancer and may represent a possible remedy to overcome hormonal resistance of hormone-independent breast tumors.
The relationship between diet and breast cancer in men Cancer Causes & Control, April 1999
The present case-control study was designed to examine the associations between food and beverage consumption and the development of breast cancer in men. The study, which was conducted between 1983 and 1986, included 200 male breast cancer cases, which were found using 10 population-based cancer registries. A total of 291 controls were selected by random-digit dialing (< age 65) and Medicare beneficiary lists (> or = age 65). The only trend found with increasing intakes of specific foods was an increase in breast cancer risk with consumption of citrus fruits. Similarly, no increase in risk with increasing amounts of specific fats, vitamins, or minerals, or with protein, fiber, carbohydrate, starches, nitrites, or alcohol consumed was found, except for an increase in risk associated with dietary vitamin C consumption. However, a decreasing trend in risk with dietary niacin and with coffee, and an increasing trend in risk with tea consumption were seen. No associations were found between risk of breast cancer and use of any dietary supplements, including vitamin C. The authors comment that the study findings are inconsistent with those from studies of breast cancer in women and probably do not represent causal relationships. Furthermore, they conclude that dietary factors are unlikely to be strong determinants of breast cancer in men.
