Adherence to high-quality dietary patterns, characterized by plant-based proteins, whole grains, and unsaturated fats, reduces the risk of coronary heart disease by 13–15% compared to adherence to low-quality dietary patterns, regardless of whether the diet is classified as low-carbohydrate or low-fat.

Study: Effect of Low-Carbohydrate and Low-Fat Diets on Metabolomic Indices and Coronary Heart Disease in U.S. Individuals.

This study found that eating healthy versions of low-carb or low-fat diets — full of plants, whole grains, and good fats — lowers heart disease risk by about 13–15%, no matter which diet you pick. So yes, quality matters more than whether you cut carbs or fat.

Study: The Benefits of Plant-Based Diets in Lowering Cholesterol Levels and Promoting Heart Health

This study shows that eating lots of plants like veggies, whole grains, and nuts helps lower bad cholesterol and keeps your heart healthy — which matches what the claim says about good diets reducing heart disease.

Study: Effects of dietary fats versus carbohydrates on coronary heart disease: A review of the evidence

This study says eating whole grains, healthy fats from plants and fish, and avoiding junk food lowers heart disease risk — which is exactly what the claim says, no matter if you eat fewer carbs or fewer fats.