Low-fat or low-carb diets may both help heart health

A long-term study of about 198,473 adults found that healthy versions of both low-fat and low-carb diets were linked with lower risk of coronary heart disease, while unhealthy versions were linked with higher risk.

New research reports that healthy forms of both low-fat and low-carbohydrate diets were associated with reduced risk of coronary heart disease, while less healthy versions were linked with higher risk. The analysis used diet questionnaires collected over more than 30 years and was published in the Journal of the American College of Cardiology. Researchers combined data from three long-running U.S. cohorts of health professionals and examined blood metabolites in a subset of participants. The study focused on coronary heart disease and did not assess other heart conditions. Key findings: - Study population included 198,473 adults from the Nurses' Health Study, Nurses' Health Study II, and the Health Professionals Follow-Up Study after excluding people with prior diabetes, cardiovascular disease or cancer. - Follow-up exceeded 30 years, during which 20,033 participants developed confirmed coronary heart disease. - People most adherent to a healthy low-carb pattern had a 15% lower risk of coronary heart disease compared with the least adherent; those most adherent to a healthy low-fat pattern had a 13% lower risk. - Unhealthy low-carb diets were associated with a 14% higher risk and unhealthy low-fat diets with a 12% higher risk; an animal-based low-carb pattern was associated with a 7% higher risk. - Blood metabolite measurements from more than 11,000 participants aligned with the diet-based findings and provided objective biochemical support. Summary: The study indicates that the quality of foods within low-fat or low-carb patterns is linked to coronary heart disease risk, with plant-based, whole-food patterns associated with lower risk and diets higher in refined carbohydrates or animal fats associated with higher risk. The metabolite data provided objective confirmation of the associations. Limitations noted by the authors include reliance on self-reported diet data, imperfect adjustment for other factors, and a study population made up of health professionals, which may limit generalizability. Undetermined at this time.