Food Quality Matters More Than Carbs or Fat for Heart Health: Study
- For decades, the optimal dietary approach to heart health has been a subject of debate, often framed as a choice between low-carbohydrate and low-fat diets.
- A new study, published in JACC, the flagship journal of the American College of Cardiology, analyzed data from nearly 200,000 U.S.
- “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,...
For decades, the optimal dietary approach to heart health has been a subject of debate, often framed as a choice between low-carbohydrate and low-fat diets. However, emerging research suggests that the quality of food consumed, rather than simply the quantity of macronutrients restricted, is the most critical factor in protecting against coronary heart disease.
A new study, published in JACC, the flagship journal of the American College of Cardiology, analyzed data from nearly 200,000 U.S. Adults over a period exceeding 30 years. Researchers found that both low-carbohydrate and low-fat diets could be heart-healthy, but only when built around nutrient-dense, wholesome foods. Conversely, diets emphasizing refined carbohydrates and animal products were linked to increased risk.
Why Food Sources Matter
“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 efficacy of low-carb and low-fat diets in reducing CHD risk is a topic of ongoing debate, and past studies showed mixed findings.”
Wu noted that previous research may have yielded inconsistent results due to the wide variability in how individuals implement these dietary patterns. Some prioritize plant-based foods, whole grains, and healthy fats, while others rely more heavily on processed foods and animal-based fats. “Focusing only on nutrient compositions but not food quality may not lead to health benefits,” he said.
A Large, Long-Term Study
To investigate this further, the research team analyzed data from three large, ongoing cohort studies: the Nurses’ Health Study (NHS), NHSII, and the Health Professionals Follow-up Study. This combined dataset encompassed 198,473 participants and more than 5.2 million person-years of follow-up, during which 20,033 cases of coronary heart disease were recorded.
Participants’ dietary habits were assessed using food frequency questionnaires. The researchers then developed scoring systems to differentiate between healthier and less healthy versions of both low-carbohydrate and low-fat diets, based on the types of foods consumed and their overall nutritional value.
Healthy vs. Unhealthy Dietary Patterns
The analysis revealed several key patterns:
- Healthy versions of both low-carbohydrate and low-fat diets – those rich in plant-based foods, whole grains, and unsaturated fats – were associated with a significantly lower risk of CHD.
- Unhealthy versions, characterized by high intakes of refined carbohydrates and animal-based fats and proteins, were linked to a greater risk of CHD.
- Higher-quality diets were also associated with more favorable metabolic markers, including lower triglyceride levels, higher HDL cholesterol, and reduced inflammation.
- Metabolomic testing – an analysis of the small molecules produced during metabolism – corroborated these findings, revealing distinct biomarker patterns among individuals following healthier dietary patterns.
“These results suggest that healthy low-carbohydrate and low-fat diets may share common biological pathways that improve cardiovascular health,” Wu said. “Focusing on overall diet quality may offer flexibility for individuals to choose eating patterns that align with their preferences while still supporting heart health.”
Study Limitations and Broader Implications
The researchers acknowledged certain limitations to their study. The findings may not be generalizable to extremely restrictive diets, such as ketogenic diets, due to the range of macronutrient intakes observed in the study population. Dietary information was self-reported, which is subject to recall bias. Finally, the study participants were primarily health professionals, a group generally more health-conscious and with better access to healthcare, potentially limiting the broad applicability of the results, although the underlying biological mechanisms are likely to be consistent across populations.
Harlan M. Krumholz, MD, Editor-in-Chief of JACC, emphasized the significance of the study’s findings. “This study helps move the conversation beyond the long-standing debate over low-carbohydrate versus low-fat diets,” he said. “The findings show that what matters most for heart health is the quality of the foods people eat. Whether a diet is lower in carbohydrates or fat, emphasizing plant-based foods, whole grains, and healthy fats is associated with better cardiovascular outcomes.”
The study, conducted by researchers at Harvard T.H. Chan School of Public Health and published on , reinforces the importance of a holistic approach to dietary health, prioritizing food quality over strict macronutrient restrictions. It suggests that individuals can achieve optimal heart health by focusing on incorporating more whole, unprocessed foods into their diets, regardless of whether they choose to follow a low-carbohydrate or low-fat eating plan.