Low-carb or low-fat? Food quality is more important for heart health

When it comes to heart health, focusing on food quality may be more beneficial than cutting carbs or fats. A major new study that tracked nearly 200,000 people over several decades found that the quality of food – not just the type of diet – makes a big difference for the heart.

The study was led by researchers at the Harvard T.H. Chan School of Public Health. “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 Qi Sun’s lab.

“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.”

Food quality and heart health outcomes

The experts analyzed data from three large groups: 43,430 men from the Health Professionals Follow-Up Study (1986–2016), 64,164 women from the Nurses’ Health Study (1986–2018), and 92,189 women from the Nurses’ Health Study II (1991–2019).

Over decades, the researchers tracked participants’ diets and recorded who developed heart disease.

Participants filled out detailed questionnaires about their eating habits. Based on the answers, the team assigned scores to indicate how healthy or unhealthy their food choices were within either a low-carbohydrate or low-fat framework.

The researchers classified foods based on nutrient quality. Whole grains, fruits, vegetables, nuts, and legumes were considered high-quality. Meanwhile, foods like potatoes, refined grains, saturated fats, and animal-based proteins were classified as low-quality.

Diet quality and metabolic health

For over 10,000 participants, the researchers went a step further. They measured hundreds of blood metabolites to see how diet quality affected metabolic regulation.

“This approach allowed us to better understand the biological effects of these diets and strengthened our findings,” said Wu.

The results were clear. Participants who stuck to healthy low-carb or low-fat diets had a lower risk of coronary heart disease.

Those who followed unhealthy versions of these diets faced a higher risk. In fact, choosing high-quality foods lowered heart disease risk by about 15 percent.

Food quality tips for a healthy heart

“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.”

For anyone looking to make healthier choices, the advice is straightforward. Add more whole grains, fruits, vegetables, nuts, and legumes to your meals. Cut back on processed meats, refined carbohydrates, and sugary snacks.

Reading food labels can also help you spot hidden ingredients like added sugars in juices and packaged foods.

Linking diet to health conditions

The researchers aren’t stopping here. They plan to explore other factors that could influence the link between diet and heart health.

The experts are interested in how genetics, lifestyle choices, and additional metabolic markers might shape these associations. They also want to see how these diets affect other health conditions like type 2 diabetes and cancer.

Understanding these connections could lead to more personalized dietary advice based on an individual’s unique health profile.

Focus on food quality every day

Although the study points out the long-term advantages of superior diets, adopting these changes is daunting in the beginning. The secret is to begin small.

Replacing white rice with brown rice, opting for whole-grain bread over white, or including one additional serving of vegetables at supper can establish healthier habits incrementally.

Preplanned meals are another effective strategy. Creating a shopping list focused on whole foods can reduce impulse purchases of processed treats.

Cooking at home more often puts more power in your hands when it comes to using ingredients, and it’s easier to steer clear of hidden sugars and unhealthy fats.

Experts also suggest considering balance, not restriction. Rather than eliminating entire categories of foods, try to put half your plate of food towards fruits and vegetables, a quarter towards whole grains, and a quarter towards lean protein or legumes.

Small, regular changes in the quality of food can lead to dramatic gains in heart health over the long term.

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