Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies

Abstract

Background Epidemiologic studies examining the relations between dairy product and calcium intakes and breast cancer have been inconclusive, especially for tumor subtypes. Objective To evaluate the associations between intakes of specific dairy products and calcium and risk of breast cancer overall and for subtypes defined by estrogen receptor (ER) status. Method We pooled the individual-level data of over 1 million women who were followed for a maximum of 8–20 years across studies. Associations were evaluated for dairy product and calcium intakes and risk of incident invasive breast cancer overall (n = 37,861 cases) and by subtypes defined by ER status. Study-specific multivariable hazard ratios (HRs) were estimated and then combined using random-effects models. Results Overall, no clear association was observed between the consumption of specific dairy foods, dietary (from foods only) calcium, and total (from foods and supplements) calcium, and risk of overall breast cancer. Although each dairy product showed a null or very weak inverse association with risk of overall breast cancer (P, test for trend >0.05 for all), differences by ER status were suggested for yogurt and cottage/ricotta cheese with associations observed for ER-negative tumors only (pooled HR = 0.90, 95% CI: 0.83, 0.98 comparing ≥60 g/d with <1 g/d of yogurt and 0.85, 95% CI: 0.76, 0.95 comparing ≥25 g/d with <1 g/d of cottage/ricotta cheese). Dietary calcium intake was only weakly associated with breast cancer risk (pooled HR = 0.98, 95% CI: 0.97, 0.99 per 350 mg/d). Conclusion Our study shows that adult dairy or calcium consumption is unlikely to associate with a higher risk of breast cancer and that higher yogurt and cottage/ricotta cheese intakes were inversely associated with the risk of ER-negative breast cancer, a less hormonally dependent subtype with poor prognosis. Future studies on fermented dairy products, earlier life exposures, ER-negative breast cancer, and different racial/ethnic populations may further elucidate the relation.

Dairy consumption and risks of total and site-specific cancers in Chinese adults: an 11-year prospective study of 0.5 million people

“…Several large prospective studies, including meta-analyses of these studies, of primarily Western populations have examined the associations of dairy intake with cancer risks, showing an inverse association with colorectal cancer [6], positive association with risk of prostate cancer [7] but lack of clear associations with risks of breast [8] and many other site-specific cancers [9]. Based on the available evidence, the World Cancer Research Fund/ American Institute for Cancer Research (WCRF/AICR) concluded that although the overall evidence on the dairy and cancer relationship is still inconsistent, there is strong evidence supporting the probable protective role of dairy products in the incidence of colorectal cancer and limited evidence suggesting that higher dairy intake is associated with higher prostate cancer risk [5].…”

Dairy consumption and risk of esophagus cancer in the prostate, lung, colorectal, and ovarian cohort

“…Protein, fat, and minerals are abundant in dairy products. Researchers have investigated the role of milk in the etiology of colon, breast, and prostate cancers (23)(24)(25); however, there is no information on its association with EC risk in the US. According to a 2016 report from the World Cancer Research Fund and the American Institute for Cancer Research, there is "limitedno conclusion" regarding the link between dairy consumption and EC.…”

The involvement of oncobiosis and bacterial metabolite signaling in metastasis formation in breast cancer

“…Altogether, these data point out a possible role of managing the microbiome to provide novel leverage on breast cancer. These strategic considerations encompass the use of prebiotics [36], probiotics [37][38][39][40][41][42][43][44][45], diverse nutrition [46][47][48][49], and the careful use antibiotics to reduce the risk for breast cancer incidence and recurrence [22][23][24][25][26][27][28][29][30][31][32][33].…”

“…The causative role of oncobiosis in the pathogenesis of breast cancer is underscored by the observations that antibiotic use increases the risk for breast cancer in mice [22][23][24], and the majority of studies suggest an increased risk in humans, also [25][26][27][28][29][30][31][32][33] (it should be noted that [34] and [35] found no association between antibiotic exposure and breast cancer risk). In further support of the pathological role of the microbiome, prebiotics [36], probiotics [37][38][39][40][41][42][43][44][45], and diverse nutrition [46][47][48][49] reduce the risk of breast cancer. Furthermore, risk factors of breast cancer, such as high-density breast [50], early menarche [51], low physical activity [51], increases in BMI [51,52], age [53], and alcohol consumption [54], are also associated with microbiome changes culminating in breast cancer-associated oncobiosis.…”