Influence of Body mass index on breast cancer risk related dietary patterns among women in Northern Tanzania: a case-control study

Irmgard Jordan, Antje Hebestreit, Britta Swai, Michael B. Krawinkel
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Introduction: Breast cancer is the leading cause of death among women worldwide. Studies in industrialised countries identified age at menarche, age at first full-term pregnancy, lactation and a high Body Mass Index as determining factors in the aetiology of breast cancer.

Methods: 115 female breast cancer patients (cases) and 230 age- and districtmatched women clinically free from breast cancer (controls) were interviewed about their reproductive history and socioeconomic condition. Semi-structured interviews including anthropometric measurements were conducted by trained enumerators. A validated Food Frequency Questionnaire was used to assess the dietary intake. The logistic risk model included women’s age, socioeconomic situation, age at menarche, age at first child, BMI, lifelong lactation and two sets of dietary patterns. The dietary patterns were obtained using principal component analysis with Varimax rotation.

Results: The adjusted logistic regression estimated an increased risk for a “Fatty Diet”, characterized by a higher consumption of milk, vegetable oils and fats, butter, lard, and red meat (OR = 1.42, 95% CI 1.08-1.87; P = 0.01), and for a “Fruity Diet” characterized by a higher consumption of fish, mango, papaya, avocado, and watery fruits (OR = 1.61, 95% CI 1.14-2.28; P = 0.01). Both diets showed an inverse association with the ratio between polyunsaturated and saturated fatty acids (P/Sratio). After stratification into the body mass index groups < 24kg/m², 24-26kg/m² and >26kg/m² a risk association of any dietary pattern could only be confirmed for the Fatty Diet among women with a body mass index above 26kg/m² (OR = 1.69, 95% CI 1.01-2.82; P = 0.05) .

Conclusion: A diet with a low P/S ratio seems to be more important for the development of breast cancer than total fat intake. However, this risk association can be considered affirmed among women with a body mass index above 26kg/m² only.