Abstract

Breast density (BD) is one of the major risk factors for breast cancer (BC) and has the potential to be used as an early marker. Puberty is a critical period for carcinogenesis, and identifying events that modify BD during this stage could aid in understanding future BC risk. The consumption of ultra-processed foods (UPFs) has been associated with BC; however, evidence of their effect on BD, particularly in adolescents, is lacking. To assess the association between the intake of UPFs during the peripubertal period and BD measured at 4 years after menarche onset, absolute fibroglandular volume (AFGV) and the percentage of fibroglandular volume (%FGV) were used. The Growth and Obesity Cohort Study is a longitudinal study of 550 girls recruited in 2006 at daycare centers in the southeastern area of Santiago, Chile. We measured the %FGV and AFGV via dual-energy X-ray absorptiometry (DXA) 4 years after menarche. Girls had at least one 24-h dietary recall survey (R24H) during the peripubertal period. Simple and multiple linear regression models were used to evaluate the associations between UPF consumption (calories and grams, categorized in quartiles according to the sample distribution) and BD outcomes, adjusting for confounders such as birth weight, body mass index, tobacco use, physical activity, menstrual cycle stage, maternal education, age at menarche, total energy consumption, and maternal BD. Data from 330 girls revealed an average daily intake of 1849 kcal (41.67% from UPFs). No consistent associations were observed between UPF intake and %FGV and AFGV.]. Stratification by menstrual cycle phase revealed a significant increase in %FGV and AFGV for Q2 vs. Q1 UPF intake as a percentage of grams in the follicular stage [?: 0.12; 95% CI 0.01, 0.22 and ?: 0.25; 95% CI 0.07, 0.43, respectively]. UPF consumption during puberty showed no consistent association with BD, except in girls whose UPF consumption was measured during the follicular phase. Further studies are needed to confirm these findings and understand the effects of food processing on BD. © The Author(s) 2025.