Seasons can affect human inflammatory status and the occurrence of diseases, and foods may also have differential impacts on inflammation across seasons; however, few studies have investigated whether there are independent and joint impacts of seasons and red meat, fruit and vegetable intakes on inflammation in breast cancer survivors. We conducted a cross-sectional study by leveraging a large cohort, the Women’s Healthy Eating and Living (WHEL) study. The WHEL study comprised primarily early stage breast cancer survivors and collected blood samples, dietary intake, demographic, and health status information at baseline. We selected 2919 participants who provided baseline dietary information and had measurement of C-reactive protein (CRP), a general marker of inflammation. In our multivariable-adjusted analyses, we found that red meat intakes were positively associated, while fruit and vegetable intakes were inversely associated with CRP; blood collected in the winter season was associated with lower CRP when compared to summer; and increased smoking intensity and body mass index (BMI) as well as having cardio-metabolic conditions (such as heart disease or diabetes) were positively associated with CRP. Furthermore, we examined the joint associations of food intakes and the season of blood draw with CRP in different subgroups. We found that moderate intakes of red meat were associated with a reduction of CRP in winter but not in other seasons; increased intakes of fruit and vegetables were associated with reduced inflammation in most seasons except winter. These associations were observed in most subgroups except past smokers with pack-years ≥ 15, in whom we observed no benefit of red meat intakes in winter. Our study provides valuable evidence for considering seasonal impacts on inflammation and seasonal food impacts in different subgroups among breast cancer survivors. The results of our study are in line with one of the emphases of the current NIH 2020–2030 nutrition strategy plan—namely, pay attention to what, when, and who should eat.

Objectives Seasons can affect human inflammatory status and the occurrence of diseases, and foods may also have differential impacts on inflammation across seasons; however, few studies have investigated whether there are independent and joint impacts of seasons and red meat, fruit and vegetable intakes on inflammation in breast cancer survivors. Methods We conducted a cross-sectional study by leveraging a large cohort, the Women's Healthy Eating and Living (WHEL) study. The WHEL study comprised primarily early stage breast cancer survivors and collected blood samples, dietary intake, demographic, and health status information at baseline. We selected 2919 participants who provided baseline dietary information and had measurement of C-reactive protein (CRP), a general marker of inflammation. Results In our multivariable-adjusted analyses, we found that red meat intakes were positively associated, while fruit and vegetable intakes were inversely associated with CRP; blood collected in the winter season was associated with lower CRP when compared to summer; and increased smoking intensity and body mass index (BMI) as well as having cardio-metabolic conditions (such as heart disease or diabetes) were positively associated with CRP. Furthermore, we examined the joint associations of food intakes and the season of blood draw with CRP in different subgroups. We found that moderate intakes of red meat were associated with a reduction of CRP in winter but not in other seasons; increased intakes of fruit and vegetables were associated with reduced inflammation in most seasons except winter. These associations were observed in most subgroups except past smokers with pack-years 15, in whom we observed no benefit of red meat intakes in winter. Conclusions Our study provides valuable evidence for considering seasonal impacts on inflammation and seasonal food impacts in different subgroups among breast cancer survivors. The results of our study are in line with one of the emphases of the current NIH 2020–2030 nutrition strategy plan—namely, pay attention to what, when, and who should eat. Funding Sources TRDRP.