New study highlights importance of diet quality for heart health

A large new study suggests that when it comes to reducing the risk of heart disease, the quality of food people eat may be more important than whether they follow a low-carbohydrate or low-fat diet.

Published in the Journal of the American College of Cardiology, the research found that diets rich in whole, plant-based foods were consistently associated with a lower risk of coronary heart disease (CHD), regardless of whether they were classified as low-carb or low-fat.

The research drew on data from three major long-running cohort studies in the United States. Together, these studies included 198,473 adults, made up of 42,720 men and 155,753 women, who were followed for up to three decades. Participants were healthcare professionals and generally had a high level of health awareness.

The study also examined biological markers linked to cardiovascular health, including:

• Triglyceride levels

• HDL (“good”) cholesterol

• High-sensitivity C-reactive protein, a marker of inflammation

In addition, a subset of 1,146 participants provided blood samples for metabolomic analysis, allowing researchers to examine how diet patterns influenced metabolic processes at a molecular level.

The findings revealed a consistent pattern: diet quality, not simply macronutrient composition, was strongly linked to heart disease risk.

Among participants following low-carbohydrate diets:

• Those who prioritised vegetables, whole grains and plant-based fats had a lower risk of CHD.

• Those whose diets emphasised animal products and refined carbohydrates had a higher risk.

A similar pattern emerged among people following low-fat diets. Diets focused on whole, plant-forward foods were associated with a reduced risk of coronary heart disease, while low-fat diets high in refined carbohydrates were linked to increased risk.

Blood biomarkers supported these findings. Participants with higher-quality diets generally had lower triglyceride levels, higher HDL cholesterol, and lower levels of inflammation.

Metabolomic profiles also appeared more favourable among people consuming higher-quality diets, regardless of whether they followed a low-carb or low-fat approach.

According to lead author Zhiyuan Wu of the Harvard T.H. Chan School of Public Health, previous research on low-carb and low-fat diets has often produced conflicting results because the labels encompass a wide range of eating patterns.

This study suggests that the type and quality of foods consumed within these diets may be a key factor explaining those differences.

However, the researchers note several limitations. Dietary intake was self-reported, which can introduce inaccuracies, and the participants, being healthcare professionals, may not fully represent the wider population. The study also did not include more extreme dietary approaches such as ketogenic diets.

Overall, the findings reinforce a growing body of evidence suggesting that focusing on whole, minimally processed foods, particularly plant-based options, may be central to supporting long-term cardiovascular health.