Low-carbohydrate diet score and risk of breast cancer: findings from a prospective cohort study

Background: A low carbohydrate diet (LCD) reflects a dietary pattern characterized by reduced carbohydrate intake and higher consumption of protein and fat. Evidence on the role of LCD and risk of breast cancer is inconclusive. We, therefore, prospectively examined the association between LCD scores and breast cancer risk in the Singapore Chinese Health Study (SCHS). Methods: We used data of 34,028 female participants in the SCHS, a prospective cohort study with subjects recruited in Singapore during 1993–1998 period. LCD scores were derived from the semi-quantitative food frequency questionnaire at baseline. Breast cancer cases were identified through record linkage with the Singapore cancer registry. Cox proportional hazard regression method was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for breast cancer in relation to LCD scores. Results: We identified 1,131 participants who developed breast cancer after 17.6 years of follow-up and 616,410 person-years. We found a modest inverse association between total LCD (HR_{per-SD increment} = 0.94, 95% CI: 0.89–1.00; P_trend = 0.05) and plant-based LCD scores with breast cancer risk (HR_{per-SD increment} = 0.94, 95% CI: 0.89–1.00; P_trend = 0.06). No association was found between animal-based LCD and risk of breast cancer (HR_{per-SD increment} = 0.96, 95% CI: 0.90–1.02, P_trend = 0.18). Conclusion: Our findings suggest that adherence to a LCD, particularly plant-based LCD may be protective against the development of breast cancer, highlighting the potential role of dietary modification in cancer prevention strategies.