Table 2.

Main findings on the association between the consumption of dairy products and breast cancer incidence.

Author (Year) [Ref]	Food/Intervention under Investigation	Type of Study	Participants	Assessment of Dietary Intake	Main Results
Couto E et al. (2013) [33]	Mediterranean diet	Prospective cohort study	44,840 women	FFQ	A statistically significant inverse association was reported between dairy consumption and breast cancer risk in all pre-menopausal and post-menopausal women.
Genkinger JM et al. (2013) [37]	Dairy, Ca, Vit D, and meat consumption	Prospective cohort study	52,062 African American women	FFQ	The authors observed no significant association between breast cancer and dairy intake. A negative association was shown between milk consumption and hormone receptor-negative subtypes.
Bahadoran Z et al. (2013) [38]	Dairy products	Case-control study	275 Iranian women	FFQ	An inverse correlation between breast cancer and dairy intake was found, especially for low-fat and fermented dairy products.
Li J et al. (2013) [41]	Calcium	Prospective cohort study	34,028 women	FFQ	A lack of association between calcium intake and breast cancer risk was observed, independently of the source of consumption.
Zang J et al. (2015) [32]	Dairy products	Systematic review and meta-analysis	1,600,312 participants	FFQ, diet questionnaires, and 24-h recall data interview	High and moderate dairy intake reduced breast cancer risk compared to low consumption.
Farvid MS et al. (2018) [36]	Dairy products	Observational study	90,503 pre-menopausal women for early adulthood and 44,264 women for adolescent	FFQ	A positive correlation emerged between dairy intake and hormone receptor-negative breast cancer in contrast to the negative one observed for hormone receptor-positive breast cancer subtypes.
Shin WK et al. (2019) [31]	Milk	Prospective cohort study	78,320 participants	Interviewer-administered semi-quantitive FFQ	In the pre-menopausal setting, a negative association between high daily intake of milk (≥1 serving/day) and breast cancer risk was observed compared to women with low milk consumption (<1 serving/week).
Marcondes LH et al. (2019) [35]	Animal food (red meat, poultry, fish, dairy, and egg)	Prospective cohort study	3209 participants	FFQ and physical examination	No association was observed between breast cancer and dairy consumption in post-menopausal women.
Key TJ et al. (2019) [40]	Alcohol, fruit, dietary fiber, meat, fish, milk, cheese, yogurt, eggs, vegetables, dairy protein, fat, carbohydrates, and free sugars	Prospective cohort study	691,571 post-menopausal UK women without previous cancer history	FFQ	The authors found no association between the consumption of different kinds of dairy products and breast cancer risk.
Fraser GE et al. (2020) [34]	Dairy and soy	Prospective cohort study	52,795 North American women	FFQ and structured 24-h dietary recalls for calibration study subjects	Increased risk of developing breast cancer in the 90th and 10th percentile of consumption of dairy products in both pre- and post-menopausal women. Increased risk of the development of hormone receptor-positive subtypes.
He Y et al. (2021) [22]	Dairy products (fermented, non-fermented, low-fat, and high-fat dairy products)	Meta-analysis	1,019,232 participants	FFQ, diet questionnaires, and home visits or in-depth interviews	The statistically significant protection of fermented dairy products was observed only in post-menopausal women. A statistically significant protective effect of low-fat products was shown solely in pre-menopausal women.
Aguilera-Buenosvinos I et al. (2021) [39]	Dairy products	Prospective cohort study	10,930 women	FFQ	A moderate consumption of dairy products (2–4 servings per day) was associated with decreased breast cancer incidence in the post-menopausal setting. A low intake (1–2 servings per day) of low-fat dairy products consumption reduced breast cancer risk in the pre-menopausal setting.

FFQ: food frequency questionnaire.