Diets rich in whole grains, fruits, vegetables, nuts, and legumes significantly reduce heart disease risk, while those heavy in processed and animal-based foods do the opposite
By American Society for Nutrition
A new study that followed almost 200,000 people for several decades has found that when it comes to heart health, the quality of food consumed matters as much as following a low-carbohydrate or low-fat diet. The results suggest that choosing healthy, high-quality foods is key to protecting the heart.
In the past two decades, low-carbohydrate and low-fat diets
have been promoted for their potential health benefits, such as weight
management and improved blood sugar and cholesterol levels. However, the impact
of these diets on reducing heart disease risk has remained an ongoing debate.
Healthy vs. Unhealthy Versions of Diets
“We found that what you eat on low-carb or low-fat diets
matters just as much as the diet itself,” said Zhiyuan Wu, PhD, a postdoctoral
fellow in the lab of Qi Sun, MD, ScD, at Harvard T.H. Chan School of Public
Health. “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.”
Wu presented the findings at NUTRITION 2025, the flagship
annual meeting of the American Society for Nutrition held in Orlando.
Decades-Long Data from Nearly 200,000 People
The study included 43,430 men in the Health Professionals
Follow-Up Study (1986-2016), 64,164 women in the Nurses’ Health Study
(1986-2018), and 92,189 women in the Nurses’ Health Study II (1991-2019). The
researchers followed the nearly 200,000 study participants for several decades,
tracking their dietary habits and whether they developed heart disease.
Based on information from detailed questionnaires completed
by the study participants, the researchers assigned scores indicating how
healthy or unhealthy their food choices were within low-carbohydrate and
low-fat diets.
Defining High- and Low-Quality Nutrients
The researchers classified carbohydrates, fats, and proteins
from foods such as whole grains, fruits, vegetables, nuts, and legumes as
high-quality nutrients, or healthy, while carbohydrates from potatoes and
refined grains, as well as saturated fats and proteins from animal-based foods,
were categorized as low-quality, or unhealthy.
For more than 10,000 of the study participants, the
researchers also measured hundreds of blood metabolites to assess how diet
quality influenced their metabolic regulation. “This approach allowed us to
better understand the biological effects of these diets and strengthened our
findings,” said Wu.
Diet Quality Directly Tied to Heart Risk
The analysis showed that study participants who followed a
healthy low-carbohydrate or low-fat diet had a lower risk of developing
coronary heart disease, while those on unhealthy versions saw an increased
risk. These healthy diet patterns, whether low-carbohydrate or low-fat diet,
lowered the risk of developing heart disease by about 15%.
“Our findings suggest that improving food quality is crucial
for improving heart health,” said Wu. “Regardless of whether someone follows a
low-carbohydrate or low-fat diet, emphasizing whole, minimally processed and
plant-based foods and limiting refined grain, sugar and animal foods, can
significantly reduce the risk of coronary heart disease.”
Practical Tips for Healthier Eating
For those looking to improve their diet, the researchers
suggest focusing on adding more whole grains, fruits, vegetables, nuts, and
legumes while cutting back on processed meats, refined carbs, and sugary foods.
They note that it is also important to check food labels and be mindful of
added low-quality ingredients, such as added sugars in juices and processed
snacks.
Moving forward, the researchers aim to explore additional factors that may influence the relationship between diet quality and heart health. For example, they want to look at how genetic factors, lifestyle choices, and other metabolic markers may further shape these associations. They are also interested in how low-carbohydrate or low-fat diets may impact other health outcomes, such as type 2 diabetes and cancer. This knowledge could help tailor dietary recommendations for individuals based on their unique health profiles.
