Food Quality Beats Diet Type for Heart Disease Prevention

Whether you’re team low-carb or devoted to low-fat eating, a massive new study tracking nearly 200,000 people over decades delivers a simple verdict: the quality of your food choices matters more than which diet camp you join. Harvard researchers found that people who ate minimally processed, plant-based foods reduced their heart disease risk by about 15 percent—regardless of whether they followed low-carbohydrate or low-fat approaches.

The research, spanning three major health studies from 1986 through 2019, challenges the decades-old debate about which diet reigns supreme for heart health. Instead of declaring a winner between low-carb and low-fat, the findings point to a more nuanced truth about what we put on our plates.

The Devil in the Dietary Details

“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 at Harvard T.H. Chan School of Public Health. The research team discovered that healthy versions of both diets—rich in plant foods and whole grains—protected hearts, while unhealthy versions increased disease risk.

Think of it this way: a low-carb diet built on avocados, nuts, and leafy greens differs vastly from one heavy on bacon and butter. Similarly, a low-fat approach centered on whole grains and legumes bears little resemblance to one dominated by fat-free cookies and refined pasta.

Breaking Down the Numbers

The study followed 43,430 men and 156,353 women across three landmark health studies. Participants regularly completed detailed dietary questionnaires, allowing researchers to score their food choices as healthy or unhealthy within their chosen diet framework.

Here’s how the researchers classified food quality:

High-Quality (Healthy) Foods:

• Whole grains, fruits, and vegetables
• Nuts and legumes
• Plant-based proteins and fats

Low-Quality (Unhealthy) Foods:

• Refined grains and potatoes
• Saturated fats from animal sources
• Processed meats and sugary foods

What sets this research apart? The team analyzed blood metabolites from over 10,000 participants—essentially creating a molecular snapshot of how different diet qualities affected the body’s inner workings. This biological validation strengthens the connection between food quality and heart health outcomes.

Beyond the Press Release: The Metabolic Connection

While the core findings emphasize food quality over diet type, the metabolic analysis reveals something particularly intriguing. The researchers measured hundreds of blood metabolites, providing a window into how our bodies actually process different foods. This approach allowed them to see not just whether people developed heart disease, but how their dietary choices influenced the complex biochemical pathways that govern cardiovascular health.

This metabolic profiling represents a significant advance in nutrition research. Rather than relying solely on observational data about who got sick and what they ate, the scientists could trace the biological mechanisms linking diet quality to heart disease risk—adding a layer of scientific rigor often missing from dietary studies.

Practical Takeaways for Your Plate

So what does this mean for your next grocery run? The researchers suggest focusing on whole, minimally processed foods regardless of your dietary philosophy. Whether you’re cutting carbs or trimming fat, prioritize vegetables, fruits, whole grains, nuts, and legumes while limiting processed meats, refined carbohydrates, and added sugars.

Reading food labels becomes crucial here. That “low-fat” yogurt loaded with added sugar? Not the heart-healthy choice it appears to be. The processed “low-carb” snack bar? Probably not doing your cardiovascular system any favors either.

Looking Ahead

“Our findings suggest that improving food quality is crucial for improving heart health,” Wu explained. The research team plans to explore how genetic factors and lifestyle choices might further influence these diet-heart connections. They’re also investigating whether these dietary patterns affect other health outcomes like type 2 diabetes and cancer risk.

The bottom line? Stop worrying about whether low-carb or low-fat is “better.” Instead, focus on filling your plate with real, whole foods—your heart will thank you either way. As this research demonstrates, the path to cardiovascular health isn’t about picking sides in the diet wars, but about choosing quality ingredients that nourish rather than merely fill.

The findings will be presented at NUTRITION 2025, the American Society for Nutrition’s annual meeting in Orlando, on June 1, 2025.