Discover the Secret to Heart Health: Food Quality Matters More Than Cutting Carbs and Fat

For a long time, diets low in carbohydrates and fats have been popular recommendations for improving health, managing weight, and minimizing the risk of chronic diseases like heart disease.

There has been ongoing debate in the scientific community about how effective these diets are at protecting the heart, especially given the significant variation in food quality within these diets.

Researchers at the Harvard T.H. Chan School of Public Health have recently emphasized that the quality of the food is as, if not more, important than limiting carbs or fats alone.

The extensive research involved almost 200,000 men and women from three significant U.S. cohort studies over a span of 25 years, examining their dietary habits and heart disease outcomes.

Using detailed dietary questionnaires, the researchers were able to evaluate the quality of foods in low carb and low fat diets, finding that diets emphasizing high-quality foods like whole grains, fruits, and vegetables were associated with about a 15% reduced risk of heart disease.

Conversely, diets that were low in carbs or fats but included high amounts of unhealthy items like refined grains and processed meats were linked with an increased risk of heart disease.

“Adopting healthy versions of these diets, rich in plant-based foods and whole grains, correlated with better heart health and metabolic function. In contrast, versions that included unhealthy food choices posed a higher heart disease risk,” said Zhiyuan Wu, PhD, the lead author of the study from Harvard’s Department of Nutrition.

This highlights that merely cutting carbs or fats without considering the type and quality of these nutrients could be ineffective.

The researchers also analyzed blood metabolites in over 10,000 participants to see how different diet qualities affected metabolic processes and lipid profiles in the body. The results showed distinct effects on plasma lipid species and other metabolites, crucial indicators of cardiovascular health, depending on the diet’s quality.

The study differentiated between types of low carb and low fat diets, noting that animal-based low carb diets, typically high in saturated fats and proteins from animal sources, were associated with increased heart disease risks.

Plant-based or vegetable-focused low carb diets, however, showed more favorable outcomes.

Similarly, unhealthy low fat diets that relied heavily on refined carbohydrates and sugars also increased risk, while healthy low fat diets that focused on whole foods decreased it.

Yaa Boakye, a registered dietitian nutritionist and nutrition consultant, likens food quality to a grading system for the body. Boakye was not involved in the study.

“Consider a student who is asked to write a book report without a clear grading rubric. They might complete the task, but without specific guidelines, the outcome might not meet expectations,” Boakye explained to Healthline.

Boakye pointed out that food quality serves as a similar guideline, helping the body assess and utilize what is consumed.

“It’s insufficient to simply mark a diet as ‘low carb’ or ‘low fat’. We must scrutinize the actual contents: fiber, added sugars, sodium, micronutrients, and whether they contain anti-inflammatory or proinflammatory agents,” she stated, emphasizing that carbs, fats, and proteins are just broad categories.

“A carbohydrate might be a highly refined bread roll or a fiber-dense lentil; a fat could be unhealthy trans fat or a nutritious cold-pressed olive oil,” she noted. “Focusing on food quality allows us to see these distinctions clearly.”

Boakye mentioned that when people adhere strictly to a low fat or low carb diet without considering these details, they often miss essential nutrients important for cardiovascular health.

“High sodium, added sugars, a lack of fiber, and insufficient antioxidants are significant concerns that often go unnoticed,” she added, noting that while one might meet their macronutrient targets, their diet could still promote hypertension, poor cholesterol levels, or systemic inflammation.

“A ‘low fat’ diet that lacks magnesium, potassium, and omega-3s can have adverse effects, while a ‘low carb’ diet that excludes prebiotic-rich plants or colorful fruits can compromise gut health and indirectly affect the cardiovascular system,” she concluded.

Registered dietitian Ayanna Smart, who writes for The Dementia Dietitian blog, emphasizes that a balanced diet full of high-quality foods is essential for stable blood sugar, optimal blood pressure, healthy weight, and improved cholesterol levels, all of which support heart health. Smart was not a part of the study.

She recommends using the plate model, which consists of filling half of your plate with vegetables and fruits, one-quarter with lean proteins such as meat, fish, beans, or lower-fat cheese, and the remaining quarter with whole grains.

“This approach naturally reduces the overall carbohydrate and fat content in your meals by cutting out excessive unhealthy fats commonly found in richer food items,” she told Healthline.

Smart highlighted that vegetables and fruits are rich in fiber, which helps maintain satiety and reduces the urge to snack between meals.

These food groups also provide essential nutrients like vitamins, minerals, and antioxidants that protect the heart and blood vessels. According to Smart, whole grains also contribute fiber and B vitamins.

“All this fiber aids in better controlling blood sugar,” she stated. “Poorly managed blood sugar can damage blood vessels, leading to heart disease, so better blood sugar control is crucial for reducing heart disease risk.”

Smart also noted that consuming lean proteins helps keep saturated fat intake low.

Moreover, including nuts in your diet can supply healthy polyunsaturated and monounsaturated fats, which are beneficial for managing levels of ‘bad’ low-density lipoprotein (LDL) cholesterol.

She added that a diet rich in high-quality foods will naturally have fewer highly processed items, thus reducing your intake of sodium, saturated fats, and excess calories.

“Minimizing consumption of highly processed foods is crucial for maintaining cardiovascular health as it helps manage blood pressure and reduces the risk of atherosclerosis (hardening of the arteries) and excessive weight gain,” Smart concluded.