CATEGORY: EATING FOR HEART HEALTH
When it comes to protecting your heart, the quality of the foods in a low-carbohydrate or low-fat diet appears to matter far more than the label on the diet itself. In an analysis of nearly 200,000 U.S. adults, healthier versions of both eating patterns—built around plant-based foods and whole grains—were linked to a lower risk of coronary heart disease, while less healthy versions were linked to a higher risk. Because the study tracked people’s usual habits rather than assigning diets, it shows an association, not proof of cause and effect.1
198,473 Adults Followed for About Three Decades
Researchers pooled three long-running studies—the Nurses’ Health Study, its sequel, and the Health Professionals Follow-Up Study—following 198,473 adults for up to about three decades. Every few years, participants filled out detailed questionnaires about what they ate, which let the team score how closely each person’s diet matched several versions of low-carbohydrate and low-fat eating. Crucially, those versions were graded by quality: some emphasized plant-based foods and whole grains, others leaned on animal products and refined carbohydrates. The team then counted who developed coronary heart disease—the narrowing of the arteries that supply the heart—recording 20,033 new cases, and cross-checked the dietary patterns against markers measured in blood samples.
Healthy Low-Carb Diets Linked to 15% Lower Risk
Compared with people whose diets least resembled each pattern, those who most closely followed a healthy, plant-forward low-carbohydrate diet had about 15% lower risk of coronary heart disease, and those following a healthy low-fat diet about 13% lower. The picture flipped for the less healthy versions: diets high in animal products and refined carbohydrates carried roughly 14% higher risk in the low-carbohydrate group and about 12% higher in the low-fat group. In other words, whether a diet was labeled “low-carb” or “low-fat” mattered less than the kinds of foods filling the plate.1 Scored without regard to food quality, the overall low-carbohydrate pattern was linked to slightly higher heart disease risk and the overall low-fat pattern to slightly lower risk.1
Lower Triglycerides, Higher HDL, Less C-Reactive Protein
The healthier eating patterns were also linked to a friendlier heart profile: lower triglycerides (a type of fat in the blood), higher HDL or “good” cholesterol, and lower levels of C-reactive protein, a marker of inflammation. The less healthy patterns showed the opposite. These blood signals help explain why food quality, rather than the low-carb or low-fat framing, tracked so closely with heart risk.
Observational, and Participants Were Mostly Health Professionals
Because this was an observational study, it cannot prove that eating one way causes or prevents heart disease, and the participants were mostly health professionals, so the findings may not apply to everyone. Still, the consistency across nearly 200,000 people is striking.
19 Studies of 846,589 People Found 23% Lower Risk
The same quality split shows up beyond these three cohorts. A 2026 review pooling 19 long-term studies of 846,589 people found that diets closest to a healthful plant-based pattern—built on whole grains, vegetables, fruit, nuts and legumes—were linked to about 23% lower risk of coronary heart disease, while plant-based patterns leaning on refined grains, sweets and sugary drinks were linked to about 24% higher risk.2
Key Takeaways
- In a study of nearly 200,000 adults, the quality of a low-carbohydrate or low-fat diet was linked more strongly to heart disease risk than the diet type itself.
- Versions rich in plant-based foods and whole grains were associated with lower risk; versions high in animal products and refined carbohydrates with higher risk.
- Healthier patterns also tracked with better cholesterol, triglyceride, and inflammation markers in the blood.
References
- Wu Z, Liu B, Wang X, et al. Effect of Low-Carbohydrate and Low-Fat Diets on Metabolomic Indices and Coronary Heart Disease in U.S. Individuals. Journal of the American College of Cardiology. 2026;87(20):2764–2781. link
- Kim Y, Kim Y. A plant-based diet and cardiovascular disease, coronary heart disease, and stroke: a systematic review and meta-analysis of prospective cohort studies. Nutrients. 2026;18(17):2779. link.