The quality of a low-carbohydrate or low-fat diet may matter more than the amount of carbohydrates or fat consumed when it comes to reducing heart disease risk, according to a study published Feb. 11 in JACC. Researchers found that versions of both diet patterns emphasizing macronutrients from healthy foods were associated with a lower risk of coronary heart disease (CHD), while versions high in refined carbohydrates and animal products were linked to higher risk and adverse metabolic profiles.

Zhiyuan Wu, PhD, et al., analyzed data from 198,473 participants across three large-scale cohort studies: the Nurses’ Health Study (NHS), NHSII and Health Professionals Follow-up Study. Participants were followed for a combined total of more than 5.2 million person-years, during which 20,033 cases of CHD were documented. Diet patterns were assessed using food frequency questionnaires, and indices were created to distinguish healthy and unhealthy low-carbohydrate and low-fat diets based on food sources and macronutrient quality.

Key findings include:

1. Healthy versions of both low-carb and low-fat diets, emphasizing plant-based foods, whole grains and unsaturated fats, were associated with a significantly lower risk of CHD.
2. Unhealthy versions of both diets, high in refined carbohydrates and animal-based fats and proteins, were linked to higher risk of CHD.
3. Healthy diet patterns were linked to lower triglycerides, higher HDL cholesterol and lower levels of inflammation.
4. Metabolomic analyses supported these findings, showing favorable biomarker profiles associated with healthy dietary patterns.

“These results suggest that healthy low-carbohydrate and low-fat diets may share common biological pathways that improve cardiovascular health,” Wu said. “Focusing on overall diet quality may offer flexibility for individuals to choose eating patterns that align with their preferences while still supporting heart health.”

“The findings show that what matters most for heart health is the quality of the foods people eat,” adds Harlan M. Krumholz, MD, SM, FACC, Editor-in-Chief of JACC. “Whether a diet is lower in carbohydrates or fat, emphasizing plant-based foods, whole grains, and healthy fats is associated with better cardiovascular outcomes.”