Adherence to diabetes risk reduction diet lowers risk of breast cancer

High adherence to a diabetes risk reduction diet (DRRD) helps prevent the development of breast cancer, which is likely due to less weight gain with a DRRD, suggests a study.

However, adherence to DRRD, independently of weight change, is only slightly associated with lower breast cancer risk, especially among lean women.

The study followed 88,739 women from the Nurses’ Health Study (NHS; 1980–2016) and 93,915 women from the NHSII (1991–2017). Medical records confirmed a total of 11,943 incident breast cancer cases, with subtypes determined by tissue microarray data and pathology reports. Follow-up questionnaires were used to repeatedly determine information on diet and breast cancer risk factors.

The investigators derived a DRRD score with nine factors: lower glycaemic index of diet; lower intakes of trans fat, sugar-sweetened beverages/fruit juices, and red/processed meat; higher intakes of cereal fibre, coffee, nuts, and whole fruits; and a higher ratio of polyunsaturated to saturated fat (score range, 9–45). Cox proportional hazards models were generated to calculate multivariable-adjusted hazard ratios (MVHRs) and 95 percent confidence intervals (CIs).

Individuals in the highest compared with the lowest DRRD adherence quintile had a modestly lower risk of breast cancer (MVHR_Q5vsQ1, 0.89, 95 percent CI, 0.84–0.95; p_trend=0.0002). This was attenuated after adjusting for weight change since age 18 years (MVHR_Q5vsQ1, 0.92, 95 percent CI, 0.87–0.98; p_trend=0.01).

The inverse association was strongest among women with current BMI <25 kg/m² (MVHR_Q5vsQ1, 0.89, 95 percent CI, 0.81–0.98; p_trend=0.004; p_interaction=0.04). Moreover, the strongest inverse association among tumour molecular subtypes was seen with basal-type tumours (MVHR_Q5vsQ1, 0.67, 95 percent CI, 0.45–1.01; p_trend=0.04).