Low-Carb Diets and the Risk of Postmenopausal Breast Cancer
Low-Carb 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.
Recent data on the use of whole-diet approaches to evaluate the association between diet and breast cancer risk have suggested that adherence to a prudent or healthy eating pattern reduced the risk. Such patterns are usually characterized by high intakes of fruits, vegetables, whole grains, and lean meats. However, patterns are identified a posteriori and only reflect existing eating patterns in the population. Using preestablished diet quality scores, we have previously shown that several diets that emphasized plant foods were associated with a lower risk of estrogen receptor-negative (ER−) postmenopausal breast cancer. Although we additionally observed an inverse association between combined intake of vegetables and legumes and ER− tumors, results for fruit and vegetable intakes from other studies were less consistent; however, many of those studies did not conduct separate analyses by the estrogen receptor status of the tumors.
The Dietary Approaches to Stop Hypertension (DASH) diet emphasizes the intake of plant foods and is promoted by the US Department of Agriculture as a healthy eating pattern for the general public. This diet encourages the eating of plant proteins, fruits and vegetables, and a moderate amount of low-fat dairy products and limiting sugary foods and sodium. Dietary scores that reflect adherence to a DASH-style diet have been linked to a lower risk of colorectal cancer. However, this score has not been evaluated in relation to breast cancer risk.
On the other hand, breast cancer development may, like colon cancer, also be mediated by the mitotic effect of insulin and insulin-like growth factors. Low-carbohydrate diets might have a low glycemic load, but they can vary greatly because they can be either plant-based or animal-based. Their potential to influence breast cancer development also has not been evaluated.
In the present analysis, we prospectively examined the association among the DASH score, low-carbohydrate diets (overall, animal-based, and plant-based), and the risk of postmenopausal breast cancer in a large ongoing cohort. In addition, we explored the association between major plant food-group contributors to these diets and their associations with breast cancer. Because we have previously noted differences in association when stratifying by estrogen receptor status, we also separately analyzed estrogen receptor-positive (ER+) tumors and ER− tumors.
Abstract and Introduction
Abstract
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.
Introduction
Recent data on the use of whole-diet approaches to evaluate the association between diet and breast cancer risk have suggested that adherence to a prudent or healthy eating pattern reduced the risk. Such patterns are usually characterized by high intakes of fruits, vegetables, whole grains, and lean meats. However, patterns are identified a posteriori and only reflect existing eating patterns in the population. Using preestablished diet quality scores, we have previously shown that several diets that emphasized plant foods were associated with a lower risk of estrogen receptor-negative (ER−) postmenopausal breast cancer. Although we additionally observed an inverse association between combined intake of vegetables and legumes and ER− tumors, results for fruit and vegetable intakes from other studies were less consistent; however, many of those studies did not conduct separate analyses by the estrogen receptor status of the tumors.
The Dietary Approaches to Stop Hypertension (DASH) diet emphasizes the intake of plant foods and is promoted by the US Department of Agriculture as a healthy eating pattern for the general public. This diet encourages the eating of plant proteins, fruits and vegetables, and a moderate amount of low-fat dairy products and limiting sugary foods and sodium. Dietary scores that reflect adherence to a DASH-style diet have been linked to a lower risk of colorectal cancer. However, this score has not been evaluated in relation to breast cancer risk.
On the other hand, breast cancer development may, like colon cancer, also be mediated by the mitotic effect of insulin and insulin-like growth factors. Low-carbohydrate diets might have a low glycemic load, but they can vary greatly because they can be either plant-based or animal-based. Their potential to influence breast cancer development also has not been evaluated.
In the present analysis, we prospectively examined the association among the DASH score, low-carbohydrate diets (overall, animal-based, and plant-based), and the risk of postmenopausal breast cancer in a large ongoing cohort. In addition, we explored the association between major plant food-group contributors to these diets and their associations with breast cancer. Because we have previously noted differences in association when stratifying by estrogen receptor status, we also separately analyzed estrogen receptor-positive (ER+) tumors and ER− tumors.
