Adherence to the South African food based dietary guidelines may reduce breast cancer risk in black South African women: the South African Breast Cancer (SABC) study

Objective: To determine the level of adherence and to assess the association between higher adherence to the South African food based dietary guidelines (SAFBDG) and breast cancer risk. Design: Population-based, case-control study (the South African Breast Cancer study) matched on age and demographic settings. Validated questionnaires were used to collect dietary and epidemiological data. To assess adherence to the SAFBDG, a nine-point adherence score (out of eleven guidelines) was developed, using suggested adherence cut-points for scoring each recommendation (0 and 1). When the association between higher adherence to the SAFBDG and breast cancer risk was assessed, data-driven tertiles among controls were used as cut-points for scoring each recommendation (0, 0 center dot 5 and 1). OR and 95 % CI were estimated using multivariate logistic regression models. Setting: Soweto, South Africa. Participants: Black urban women, 396 breast cancer cases and 396 controls. Results: After adjusting for potential confounders, higher adherence (>5 center dot 0) to the SAFBDG v. lower adherence (<3 center dot 5) was statistically significantly inversely associated with breast cancer risk overall (OR = 0 center dot 56, 95 % CI 0 center dot 38, 0 center dot 85), among postmenopausal women (OR = 0 center dot 64, 95 % CI 0 center dot 40, 0 center dot 97) as well as for oestrogen-positive breast cancers (OR = 0 center dot 51, 95 % CI 0 center dot 32, 0 center dot 89). Only 32 center dot 3 % of cases and 39 center dot 1 % of controls adhered to at least half (a score >4 center dot 5) of the SAFBDG. Conclusions: Higher adherence to the SAFBDG may reduce breast cancer risk in this population. The concerning low levels of adherence to the SAFBDG emphasise the need for education campaigns and to create healthy food environments in South Africa to increase adherence to the SAFBDG.