If you’re focused on heart health, you may have considered adjusting your diet, perhaps by reducing carbohydrate or fat intake. However, new research suggests that simply cutting back on these macronutrients isn’t enough. The quality of your diet – the types of carbohydrates and fats you choose – appears to be a more significant factor in reducing your risk of heart disease.
A study published on , in the Journal of the American College of Cardiology, analyzed data from nearly 200,000 participants across three large, long-term studies. Researchers at Harvard University examined the relationship between dietary patterns, metabolic profiles, and the incidence of coronary heart disease (CHD) over more than 30 years of follow-up.
The findings revealed that healthy versions of both low-carbohydrate and low-fat diets were associated with a significantly lower risk of CHD. These healthy dietary patterns were characterized by an emphasis on plant-based foods, whole grains, and unsaturated fats. Conversely, unhealthy versions of these same diets – those high in refined carbohydrates and animal fats and proteins – were linked to a higher risk of CHD and unfavorable metabolic profiles.
“Our findings highlighted that it’s not simply about cutting carbs or fat, but it’s about the quality of foods people choose to construct those diets,” explained Zhiyuan Wu, a postdoctoral research fellow at the Harvard T.H. Chan School of Public Health and lead author of the study.
The study’s methodology involved analyzing data from the Nurses’ Health Study (NHS), NHSII, and the Health Professionals Follow-up Study. Participants completed detailed food frequency questionnaires, allowing researchers to categorize their diets based on the quality of carbohydrate and fat sources. Researchers also went further, analyzing blood samples from over 11,000 participants to measure metabolites – small molecules that provide insights into metabolic processes – which corroborated the dietary findings.
“They obtained results with a particularly rigorous or complex methodology,” noted Camilla Dalby Hansen, a researcher at the University of Southern Denmark in Odense, who was not involved in the study. “The fact that they included metabolites in their analysis pleases me. It’s new and exciting.”
Understanding Macronutrients and Food Quality
Our bodies require macronutrients – carbohydrates, proteins, and fats – for energy and overall health. These are found in a wide variety of foods, from red meat and fruits to oatmeal, fast food, and vegetables. However, the nutritional value of these foods varies considerably.
The Harvard researchers distinguished between processed, lower-quality carbohydrates and high-quality carbohydrates like whole grains. Similarly, they differentiated between healthy unsaturated fats (found in avocados and nuts) and less healthy saturated fats (found in red meat, heavy cream, and butter). Lower-quality fats are often more difficult for the body to metabolize and have been linked to an increased risk of type 2 diabetes and heart disease.
“Fats are the most incredible macronutrients,” Hansen said. “They benefit brain health, hormonal function and skin. They also have a cardio-protective effect, [as they] clear your arteries from debris.”
Defining Healthy and Unhealthy Dietary Patterns
The researchers categorized diets into “healthy” and “unhealthy” groups. Healthy diets included more plant-based proteins and fats, as well as high-quality carbohydrates. Unhealthy diets were characterized by a higher intake of processed carbohydrates and animal proteins and fats.
The study found that healthy low-carb and low-fat diets were associated with lower levels of triglycerides, higher levels of high-density lipoprotein (HDL) cholesterol (often referred to as “good” cholesterol), and reduced inflammation – all indicators of improved cardiovascular health. The metabolomic analyses further supported these findings, revealing favorable biomarker profiles associated with the healthy dietary patterns.
What Does This Mean for Your Diet?
This research reinforces the idea that a holistic approach to diet is crucial for heart health. Simply focusing on reducing overall carbohydrate or fat intake may not be sufficient. Instead, prioritizing food quality – choosing whole, unprocessed foods rich in plant-based nutrients and healthy fats – appears to be the key.
While this study was observational and cannot definitively prove cause and effect, the large sample size and long duration of follow-up strengthen the findings. The inclusion of metabolomic data adds another layer of evidence, supporting the link between dietary patterns and cardiovascular health.
The findings suggest that when considering dietary changes for heart health, the focus should be on what you eat, not just how much. Prioritizing whole grains, fruits, vegetables, and healthy fats over refined carbohydrates and processed foods may be a more effective strategy for reducing your risk of heart disease.
