Breast cancer is the most common cancer among women, and identifying actionable risk factors is a large public health priority. Though often diagnosed later in life, adolescence and early adulthood have been shown to be highly susceptible periods for breast cancer carcinogenesis. Most previous studies on dietary intake for breast cancer risk have focused on eating patterns in late adulthood, and may not adequately capture the potential effect of dietary patterns earlier in a woman’s life. In a recent issue of Cancer Research, Dr. Holly Harris in the Public Health Sciences Division found that consuming dietary pattern associated with inflammation early in life increased premenopausal breast cancer risk.
Despite considerable progress, there is still much to be learned about the causes of breast cancer, particularly breast cancer among young women. Said lead author Dr. Harris, “for breast cancer in younger women prior to menopause only very few risk factors are known and mechanistic insights are very limited. Moreover, in these younger women hormonal factors seem to be less relevant, pointing towards other mechanisms. As breast cancer is a process that takes many years, mostly decades, to arise we are particularly interested in risk factors during earlier phases of a woman’s life and have identified the first two decades as particularly relevant.”
One potential mechanism related to early breast cancer may be chronic inflammation, a systemic process that may increase cancer risk generally. Some dietary patterns are more likely to result in higher levels of inflammatory biomarkers such as C-reactive Protein, IL-6, and TNF-α. Previous research has identified an inflammatory dietary pattern as having higher intake of sugar-sweetened and diet soft drinks, refined grains, red and processed meat, margarine, corn, and fish. This inflammatory dietary pattern is also characterized by lower intake of green leafy vegetables, yellow vegetables, cruciferous vegetables, and coffee. Said Harris, “while the impact of diet on breast cancer risk is limited, a habitual diet during adolescence that promotes inflammation has not been studied in the context of breast cancer. We therefore derived an inflammatory diet pattern during adolescence and examined its influence, with a particular interest in premenopausal breast cancer risk.”
To evaluate this association, the authors utilized previously collected data from the Nurses’ Health Study II. In this study, over 45,000 female nurses completed a food frequency questionnaire that asked their average consumption of some 130 food and beverage items between the ages of 13-18. Though this questionnaire was given when the women were older (33-52), other research suggests these recalled diets are reproducible and valid. Over the next 22 years, nearly 1,500 of these women developed breast cancer. The authors used the responses from the questionnaires to score diets according to their inflammatory potential, and evaluate the association of an inflammatory diet with breast cancer incidence. Stratified analyses evaluated this association by menopausal status and by the hormone receptor status of the tumor.
Image from Dr. Holly Harris
Comparing the highest versus lowest quintiles of adolescent inflammatory dietary pattern score, the authors found a 35% higher risk of premenopausal breast cancer. No association was observed between an inflammatory diet and postmenopausal breast cancer, or between an inflammatory diet and all breast cancer. No significant differences were found by hormone receptor subtype. While the mechanism behind this association is unclear, these results are consistent with previous evidence that risk factor profiles are different between premenopausal and postmenopausal breast cancer. Importantly, while postmenopausal breast cancers are believed to be more strongly driven by hormonally-related risk factors, few modifiable risk factors have been identified for premenopausal breast cancer. As such, these results are an important contribution for premenopausal breast cancer prevention efforts, and highlight the importance of a healthy diet throughout the life course.
Moving forward, the authors plan to continue this line of investigation. Said Harris, “in the future we are interested in studying the impact of diet during adolescence and young adulthood on markers of future breast cancer risk as well as how other lifestyle factors during adolescence that increase inflammation influence breast cancer risk.”
Harris HR, Willett WC, Vaidya RL, Michels KB. An Adolescent and Early Adulthood Dietary Pattern Associated with Inflammation and the Incidence of Breast Cancer. Cancer Res 2017; 77(5):1179-1187. doi: 10.1158/0008-5472.CAN-16-2273.
Funding for this study was provided by the National Cancer Institute, NIH.