New research shows that diet patterns focused on high-quality, whole foods influence heart disease and stroke risk more than low-carb or low-fat labels.
A major review of decades-long diet and health records shows that diets defined solely by carbohydrate or fat content provide little heart protection unless they are based on high-quality, mostly plant-based foods. At the same time, extensive research ties dietary patterns rich in whole foods like vegetables, whole grains, legumes, nuts, and healthy fats with lower stroke risk. Both lines of evidence converge on a simple message: the kind of foods you choose shapes cardiovascular and cerebrovascular outcomes more than macronutrient percentages.
Higher-quality foods drive heart disease associations
A large analysis presented at NUTRITION 2025 investigated how healthy and unhealthy low-carbohydrate (LCD) and low-fat diets (LFD) correlate with coronary heart disease risk. Researchers from Harvard T.H. Chan School of Public Health found that healthy versions of these diets — those rich in plant-based foods and whole grains — were linked to better heart health outcomes and improved metabolic function. In contrast, low-carb and low-fat diets emphasizing unhealthy foods were associated with a higher risk of heart disease.
“Low-carbohydrate and low-fat diets have been widely promoted in the U.S. over the past two decades for weight control and metabolic health, but their effects on heart disease risk have remained unclear,” lead author Zhiyuan Wu said in a statement. “Our findings help debunk the myth that simply modulating carbohydrate or fat intake is inherently beneficial, and clearly demonstrate that the quality of foods constructing low-carbohydrate and low-fat diets is what’s most important to protect heart health.”
This work, analyzing dietary patterns among tens of thousands of adults in cohorts including the Health Professionals Follow-Up Study and the Nurses’ Health Studies, highlights that low-carb or low-fat tags alone are insufficient markers of heart health. Diets built on refined grains, processed meats, and high amounts of animal fats actually corresponded with increased cardiovascular risk, whereas versions of these eating patterns grounded in whole grains, vegetables, legumes, nuts, and plant oils were linked with more favorable metabolic and lipid profiles.
The study reaffirmed that the associations of low-carbohydrate and low-fat diets with mortality may depend on the quality and food sources of macronutrients. In other words, the source of calories matters more than whether those calories come principally from carbohydrates or fats.
In practical terms, this means that slashing carbohydrates or fats without distinguishing between refined and whole foods offers little protection. Whole food carbohydrates and unsaturated fats — from olive oil, nuts, beans, and whole grains — contribute to lowering heart disease risk, while heavily processed substitutes do not.
Diet patterns and stroke risk are also linked
The influence of food quality extends to cerebrovascular disease. A large meta-analysis pooling data from multiple cohort and case–control studies reports that people adhering more closely to a Mediterranean dietary pattern experienced significantly lower stroke risk compared with those with weaker adherence. The pooled analysis found that high adherence was associated with a hazard ratio of 0.88 for stroke, which translates to roughly a 12 percent lower risk compared with low adherence.
This association holds across numerous epidemiologic investigations and supports a broader evidence base showing that the Mediterranean pattern — emphasizing vegetables, fruits, legumes, whole grains, olive oil, and fish — is protective against multiple forms of cardiovascular disease, including stroke and myocardial infarction.
More recent data focused on female participants further illustrate these trends. In that study, women with the highest adherence to Mediterranean diet principles were 18 percent less likely to experience any stroke compared with those with lowest adherence. They were also 16 percent less likely to have an ischemic stroke and 25 percent less likely to have a hemorrhagic stroke.
The mechanisms linking high-quality diets to better heart and brain health are not fully understood, but multiple lines of evidence suggest that whole, plant-rich foods improve vascular function and reduce inflammation. These foods are high in fiber, antioxidants, and healthful fats while minimizing the intake of saturated fats and refined carbohydrates that promote adverse lipid profiles and metabolic dysfunction.
For example, diets weighted toward whole grains and unsaturated fats have been associated with improved cholesterol ratios and decreased triglycerides, both of which are favorable for cardiovascular health. Meanwhile, refined carbohydrate patterns are associated with greater fluctuations in blood sugar and increased risk for metabolic disorders, which are known risk factors for heart disease.
Researchers and clinician-scientists now advise shifting focus from chasing macronutrient ratios to promoting overall dietary quality. Rather than prescribing strict low-carb or low-fat regimens, effective guidance emphasizes patterns filled with plant-based foods, whole grains, nuts, legumes, fish, and healthful oils over processed meats, added sugars, and refined products.
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