Degree of food processing and breast cancer risk in black urban women from Soweto, South African: the SABC study

Abstract Globally, consumption of ultra-processed foods is increasing while consumption of whole foods is decreasing. This study aimed to investigate the association between consumption of ultra-processed foods, whole foods and breast cancer risk in black women from Soweto, South Africa. A population-based case (n=396)-control (n=396) study, matched on age and residence, using data from the South African Breast Cancer study. Dietary intake was assessed by using a validated quantified food frequency questionnaire (QFFQ). Food items were categorized using the NOVA system (I. unprocessed/minimally processed foods, II. culinary ingredients, III. processed foods and IV. ultra-processed foods). Conditional logistic regression models were used to estimate odds ratios and 95% confidence intervals of dietary contributions from each NOVA food group (as a percentage of total energy intake) and adjusting for potential confounding factors. Considering contributions to total energy intake per day, ultra-processed food consumption contributed to 44.8% in cases and 47.9% in controls while unprocessed/minimally processed foods contributed to 38.8% in cases and 35.2% in controls. However, unprocessed/minimally processed food consumption showed an inverse association with breast cancer risk overall (OR=0.52, 95%CI: 0.35-0.78, p-trend=0.001), as well as in in pre-and postmenopausal women separately,(OR=0.52, 95%CI: 0.27-0.95, p-trend=0.035 and OR=0.55, 95%CI: 0.35-0.89, p-trend=0.012, respectively) and in women with progesterone positive (PR+) breast cancer (OR=0.23, 95%CI: 0.06-0.86, p-trend=0.029). There was no heterogeneity in association with breast cancer when analyses were stratified according to BMI. No significant associations were observed for the consumption of culinary ingredients or processed-and-ultra-processed foods. Intake of unprocessed/minimally processed foods may reduce the risk of developing breast cancer in black women from Soweto, South Africa, so their consumption should be encouraged.