Low-carbohydrate diets, dietary approaches to stop hypertension-style diets, and the risk of postmenopausal breast cancer.

The authors prospectively examined the association between the Dietary Approaches to Stop Hypertension diet score, overall, animal-based, and vegetable-based low-carbohydrate-diet scores, and major plant food groups and the risk of postmenopausal breast cancer in 86,621 women in the Nurses' Health Study. Diet scores were calculated by using data from up to 7 food frequency questionnaires, with follow-up from 1980 to 2006. The authors ascertained 5,522 incident cases of breast cancer, including 3,314 estrogen receptor-positive (ER+) cancers and 826 estrogen receptor-negative (ER-) cancers. After adjustment for potential confounders, the Dietary Approaches to Stop Hypertension diet score was associated with a lower risk of ER- cancer (relative risk comparing extreme quintiles = 0.80, 95% confidence interval: 0.64, 1.01; P trend = 0.02). However, this was largely explained by higher intakes of fruits and vegetables. The authors also observed an inverse association between risk of ER- cancer and the vegetable-based, low-carbohydrate-diet score (corresponding relative risk = 0.81, 95% confidence interval: 0.65, 1.01; P trend = 0.03). High total fruit and low-protein vegetable intakes were associated with a lower risk of ER- cancer (relative risk comparing extreme quintiles = 0.71, 95% confidence interval: 0.55, 0.90; P trend = 0.005). No association was found between ER+ tumors and fruit and vegetable intakes. A diet high in fruits and vegetables, such as one represented by the Dietary Approaches to Stop Hypertension diet score, was associated with a lower risk of ER- breast cancer. In addition, a diet high in plant protein and fat and moderate in carbohydrate content was associated with a lower risk of ER- cancer.