The association between dietary intake and breast cancer risk in black South African women

Abstract

Background - Breast cancer is the second leading diagnosed cancer in black South African women. The World Health Organization previously estimated that 30%-50% of all cancers, including breast cancer can be prevented by following a healthy diet, being physically active and maintaining a healthy body weight. However, previous research in South Africa showed that Westernised diets, high obesity rates and low physical activity levels are seen in South Africa and may contribute to an increased breast cancer risk. The main aim of this study was to investigate the association between dietary intake and breast cancer risk in black South African women residing in Soweto, Gauteng. Methods - This retrospective, population based, case-control study included 396 breast cancer cases and 396 matched controls, participating in the South African Breast Cancer study. A validated culture-specific quantitative food frequency questionnaire was used in combination with household utensils, food portion pictures and food models to determine habitual dietary intake. Energy dense intakes were used to create 12 food groups with the help of the Condensed Food Composition Tables for South Africa. Conditional logistic regression was applied to estimate odds ratios (OR) and 95% confidence intervals (CI) to determine breast cancer risk in relation with dietary intake. Results - Four out of five women (82%) in case and control participants were either overweight or obese. Low physical activity levels were noted in case (114 METs per week) and control (110 METs per week) participants. Additionally, nearly two thirds of women were postmenopausal and 86% of this sample earned less than R3 000 per month. After adjusting for confounding factors, inverse associations with breast cancer risk were noted in fresh fruit consumption (OR=0.3, 95% CI 0.12, 0.80, premenopausal) and in red and organ meat consumption (OR=0.6, 95% CI 0.40, 0.96, OR=0.6, 95% CI 0.47, 0.91). Savoury food consumption (sauces and soups) showed an increased breast cancer risk in postmenopausal women (OR=2.1, 95% CI 1.15, 4.07). Discussion and conclusion - Fruit and organ meat contains possible protective factors against breast cancer and is less energy dense, contributing to a healthier body weight. Savoury foods may lack a variety of possible protective nutrients and are mostly energy dense. Red meat contains various nutrients that may protect against breast cancer risk. However, the association with red and organ meat consumption requires further investigation as the inverse association may be due to low consumption in this sample. Additionally, a Westernised diet and high obesity rates, co-existing with low physical activity levels in this sample are worrisome for it may contribute to an increased breast cancer risk. Therefore, inclusion of less energy dense and more nutrient rich foods (fresh fruit) is advised to be part of a balanced diet. Current health strategies should be prioritized to reduce obesity and breast cancer mortality rates in South Africa.