The phenomenon that the amount of protein in the diet can have an impact on the risk of developing breast cancer is of great concern. High protein intake contributes to the increased risk of breast cancer mainly by increasing insulin-like growth factor 1, which plays an important role in tissue growth and tumor progression. However, the nutritional characteristics of the main protein-providing foods vary, and therefore their impact on the risk of breast cancer development also varies. Results from prospective cohort studies suggest that there is no significant association between red meat intake and breast cancer risk. A pooled analysis of eight cohort studies also suggested no association between red meat intake and breast cancer risk. More recently, the results of a review, a meta-analysis of prospective cohort studies, and a prospective study did not show that red meat intake affects the risk of breast cancer. However, most of the studies on diet have targeted the time period of middle age and even old age. Researchers have recognized that age at menarche and timing of first pregnancy play a greater role in the development of breast cancer. Estrogen and progesterone receptor status in breast tumors varies, and most previous studies have assessed the association between different dietary sources of protein and breast cancer risk, but there is insufficient information to evaluate the role of hormone receptor status on breast cancer risk. After 12 years of follow-up, an early analysis of the Nurses’ Health Study II suggested an association between red meat intake and breast cancer incidence in premenopausal women, particularly in hormone receptor-positive tumors. However, it is not known where the positive results obtained from the study came from, is there language that was assessed for younger age groups? Or is it the age group that the subjects were in when the breast cancer was confirmed? This article is an analysis of the long-term follow-up results of the above study, with the aim of assessing the possible association between premenopausal red meat intake and the overall risk of breast cancer, as well as separately in premenopausal and postmenopausal female subjects. In addition, the investigators evaluated the association between breast cancer risk and tongue such as other protein-rich foods (e.g., poultry, fish, eggs, beans, and nuts). In addition, the researchers evaluated the association between red meat intake and the risk of breast cancer in subjects with different hormone receptor status. Subjects included in the study were those from the Nurses’ Health Study II who completed a questionnaire on diet in 1991. The study evaluated the incidence of invasive breast cancer, first through self-reporting by the subjects and later confirmed by pathology reports. During a 20-year follow-up period, the researchers identified 2830 breast cancer patients. The investigators found that the overall incidence of breast cancer was higher in subjects with a high intake of red meat, with a relative risk of 1.22 (highest 1/5 compared to lowest 1/5). However, no significant correlation was found between the overall incidence of breast cancer and diet in subjects with higher intakes of poultry, fish, eggs, legumes, and nuts. When assessed according to the subjects’ menstrual status, the incidence of breast cancer was lower in female subjects who consumed higher amounts of poultry in postmenopausal women (relative risk of 0.73), but the researchers did not observe this association in premenopausal female subjects. When different types of protein sources were evaluated, replacing red meat with other legumes reduced the risk of breast cancer by 15% (RR of 0.98 in all female subjects); and in premenopausal female subjects, it reduced the risk of breast cancer by 19%, with a RR of 0.81. In addition, replacing one serving of red meat with poultry reduced the overall risk of breast cancer by 11%, with an RR of 0.81. In addition, replacing one serving of red meat with poultry reduced the overall risk of breast cancer by 11%, with an RR of 0.83, and by 24% in postmenopausal women, with an RR of 0.76. Replacing one serving of red meat with a mixture of beans, nuts, poultry and fish reduced the overall risk of breast cancer by 14%, with an RR of 0.86, and by 14% in premenopausal women, with an RR of 0.86. The results of this study suggest that a high intake of red meat in early adulthood may be an important factor in the development of breast cancer. Red meat intake may be a risk factor for breast cancer development, and replacing red meat with a mixture of beans, poultry, nuts and fish reduces the risk of breast cancer development.