Associations of iron status with breast cancer risk factors in adult women: Findings from National Health and Nutrition Examination Survey 2017-2018

Objective: This study examined the association between iron status and a set of breast cancer risk factors among U.S. adult women aged 20-80 years. Methods: Data from National Health and Nutrition Examination Survey (2017-2018) were used to examine the relation between serum ferritin, serum iron and transferrin saturation with a set of breast cancer risk factors [body mass index (BMI), waist circumference, glycosylated hemoglobin (HbA1c), fasting plasma glucose, insulin and HOMA-IR]. The multivariable linear regressions were used controlling for age, race/ethnicity, menopause status, education level, smoking status, alcohol consumption, physical activity, high-sensitivity C-reactive protein (hsCRP) and total energy intake. Results: HbA1c, BMI and waist circumference data were available for 1902 women with a fasting sample (n = 913) for fasting plasma glucose, insulin and HOMA-IR. Transferrin saturation had significant, inverse associations with BMI, waist circumference and HbA1c. The size of difference observed were that participants in the fourth quartile of transferrin saturation had a 4.50 kg/m2 smaller BMI, a 9.36 cm smaller waist circumference and a 0.1 % lower HbA1c level than participants in the first quartile. Similarly, serum iron concentrations were inversely associated with BMI and waist circumference. In addition, serum iron had significant, inverse associations with insulin and HOMA-IR. Sensitivity analyses among men gave similar results. For serum ferritin, there was a trend towards a positive association between waist circumference, HbA1c and fasting plasma glucose with serum ferritin. However, the associations did not reach statistical significance among women. Conclusions: Iron status may impact breast cancer risk via effects on adiposity or glucose metabolism. The findings should be confirmed with further prospective data.