Abstract
Protein is important to the human body, and different sources of protein may have different effects on the risk of breast cancer. Thus, we conducted a meta-analysis to investigate the association between different dietary protein sources and breast cancer risk. PubMed and several databases were searched until December 2015. Relevant articles were retrieved according to specific searching criteria. Forty-six prospective studies were included. The summary relative risk (RR) for highest versus lowest intake was 1.07 (95% confidence interval (CI) 1.01–1.14, I2 = 34.6%) for processed meat, 0.92 (95% CI 0.84–1.00, I2 = 0%) for soy food, 0.93 (95% CI 0.85–1.00, I2 = 40.1%) for skim milk, and 0.90 (95% CI 0.82–1.00, I2 = 0%) for yogurt. Similar conclusions were obtained in dose-response association for each serving increase: total red meat (RR: 1.07; 95% CI 1.01–1.14, I2 = 7.1%), fresh red meat (RR: 1.13; 95% CI 1.01–1.26, I2 = 56.4%), processed meat (RR: 1.09; 95% CI 1.02–1.17, I2 = 11.8%), soy food (RR: 0.91; 95% CI 0.84–1.00, I2 = 0%), and skim milk (RR: 0.96; 95% CI 0.92–1.00, I2 = 11.9%). There was a null association between poultry, fish, egg, nuts, total milk, and whole milk intake and breast cancer risk. Higher total red meat, fresh red meat, and processed meat intake may be risk factors for breast cancer, whereas higher soy food and skim milk intake may reduce the risk of breast cancer.
Highlights
Protein is important to the human body
Egg, soy food, and milk are common and important sources of dietary protein. In this meta-analysis, we explored the effects of total red meat, fresh red meat, processed meat, poultry, fish, egg, soy food, nuts, total milk, whole milk, skim milk, and yogurt on breast cancer incidence
No n denotes the number of studies; confidence intervals (CI), confidence interval; RR, relative risk; OC, oral contraceptive; BMI: body mass index. This meta-analysis suggested that higher intake of soy food and skim milk could decrease the risk of breast cancer, and that higher intake of processed meat may increase the incidence of breast cancer
Summary
Protein is important to the human body. Protein is involved in the constitution of human tissues and the regulation of various physiological functions. It is essential for body growth and development, as well as the transport of many important substances, and the provision of biological energy. Different sources of protein might have different effects on breast cancer risk. Carcinogenic byproducts—such as heterocyclic amines and polycyclic aromatic hydrocarbons formed during the high-temperature cooking of red meat [3,4]—can increase the risk of breast cancer. In this study, we wanted to investigate the association between the consumption of different sources of dietary protein and the risk of breast cancer. We intend for this article to serve as a reference for Nutrients 2016, 8, 730; doi:10.3390/nu8110730 www.mdpi.com/journal/nutrients
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