The count stands at 20,033. That is how many cases of coronary heart disease turned up among nearly 200,000 American men and women followed for more than 30 years, and the pattern in those records is not the one most diet books sell.
A team at Harvard’s public health school in Boston published the analysis in JACC on Feb. 11, 2026. It drew on three long-running cohorts: the Health Professionals Follow-Up Study, the Nurses’ Health Study and Nurses’ Health Study II. Diets were scored for quality, participants were tracked for heart disease, and blood samples were checked for cardiovascular risk markers.
What the record shows
Cutting carbohydrates, or cutting fat, did not by itself protect anyone. What counted was the food underneath the label. Both diet types, when built on good carbohydrates and plant-based protein and fat, went with a risk of coronary heart disease about 15% lower. The same two diets, when they leaned on refined carbohydrates and animal protein and fat, went with a higher risk.
The blood work pointed the same way. People on the healthier versions of either pattern showed higher HDL, the so-called good cholesterol, and lower triglycerides. Healthline, which covered the paper, added that these eaters also had lower levels of inflammation.
Zhiyuan Wu, a postdoctoral researcher in nutrition and first author, put it bluntly. “Our findings help debunk the myth that simply modulating carbohydrate or fat intake is inherently beneficial,” he said. The diets that worked were assembled from whole grains, fruits, vegetables, nuts, legumes and olive oil, foods earlier studies had already tied to a lower heart risk.
The caveat in the design
This is observational work. Participants reported what they ate on food frequency questionnaires, and the researchers adjusted for health and lifestyle confounders, which narrows the doubt but does not remove it. The paper claims an association, nothing stronger, and its authors do not pretend otherwise.
Qi Sun, an associate professor of nutrition and epidemiology and the corresponding author, drew the practical line for doctors and patients. “Promoting an overall healthy eating pattern, rather than strict macronutrient restriction, should be a central strategy for the primary prevention of heart disease,” he said.
The cohorts run on National Institutes of Health grants. The analysis also drew support from the Dana-Farber/Harvard Cancer Center SPORE in Prostate Cancer, a detail that sits in the paper’s funding notes and not in its findings.
Sources
- Low-carb and low-fat diets associated with lower heart disease risk if rich in high-quality, plant-based foods
- Healthy Low Carb, Low Fat Diets May Improve Heart, Metabolic Health (Healthline)
