Diet and Breast Cancer Survivorship: A Scoping Review

Survival rates of breast cancer, which is the most common cancer among women, continue to improve. Diet after diagnosis has become an area of interest regarding breast cancer survival, and evidence has accumulated over past decades. Although earlier studies did not offer recommendations beyond general cancer prevention guidelines, more recent findings suggest a potential role of dietary factors in breast cancer prognosis. Healthy dietary patterns have been associated with reduced mortality from non-breast cancer causes. However, associations with breast cancer-specific mortality were less consistent in cohort studies of survivors, most of which were conducted in Western populations. Two randomized intervention trials on the effect of low-fat dietary patterns yielded inconsistent findings, with one study reporting a lower risk of breast cancer recurrence and the other showing no association. Because reduced fat intake is often accompanied by weight loss and increased intake of other dietary components, such as higher vegetable consumption, these factors need to be considered when interpreting the results. Both soy food and dietary fiber intakes have been shown to reduce the risk of all-cause mortality after breast cancer diagnosis. High circulating vitamin D levels may confer benefits, particularly among women with suboptimal vitamin D status. However, the current evidence does not support the protective effect of other individual micronutrients or dietary supplements. Sugar and carbohydrate intake, and coffee consumption remain areas of emerging research interest. In addition, the role of dietary factors should be investigated in specific subgroups, such as premenopausal women, users of antihormone therapy, and those with estrogen receptor-positive or -negative tumors. Importantly, most associations were observed predominantly in Western or postmenopausal populations and may not be generalizable to Asian or younger women. Further studies are needed to clarify the population-specific effects and strengthen the evidence base for dietary recommendations for breast cancer survivors.