Carbohydrate quality index and breast cancer risk in a Mediterranean cohort: The SUN project

Background & aims: Beyond the quantity of carbohydrate intake, further research is needed on the relevance of carbohydrate quality. Thus, we evaluated the association between an a priori defined carbohydrate quality index (CQI) and the incidence of breast cancer (BC) in a Mediterranean cohort study. Methods: We used a validated semi-quantitative 136-item food-frequency questionnaire (FFQ) in a prospective follow-up study of 10,812 middle-aged women. We evaluated at baseline the CQI following 4 criteria: dietary fiber intake, glycemic index, whole-grain:total-grain carbohydrates ratio and the solid carbohydrate:total carbohydrate ratio. Subjects were classified into quartiles according to the final CQI score. Results: During a median follow-up of 11.8 years, we confirmed 101 incident cases of BC. Our study suggests that a higher quality of carbohydrate intake, as measured by the baseline CQI, was associated with a lower risk of BC [HRQ4 vs. Q1 0.39 (95% CI 0.17, 0.87)]. Particularly, a higher whole-grain:total-grain carbohydrates ratio was associated with lower risk of BC [HRT3 vs. T1 0.56 (0.34, 0.90)]. When we stratified by menopausal status, we found an inverse association between CQI and BC in the comparison of extreme quartiles among premenopausal women. Conclusions: In this Mediterranean cohort, a better quality of dietary carbohydrate intake showed a significant inverse association with the incidence of BC, which suggests that strategies for cancer prevention should highlight the quality of this macronutrient. (C) 2020 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Automated summary

The study found that in the Mediterranean region, higher quality carbohydrate intake is associated with a lower incidence of breast cancer, particularly in those with a higher whole-grain to total grain carbohydrate ratio. Among premenopausal women, there is a negative association between carbohydrate quality and breast cancer risk.