Researchers followed over 1,700 people with heart problems for four years to see if eating healthier foods would prevent future heart attacks and strokes. They tracked six different ways of measuring diet quality, including how much processed food people ate and how many plants they included in their meals. The main finding was that people who improved their diet quality over three years had fewer heart problems. However, other diet measurement methods didn’t show the same clear benefit. This suggests that sticking with healthy eating for a long time—not just a few months—is what really helps protect your heart.

The Quick Take

  • What they studied: Whether people with heart disease who improved their eating habits over time would have fewer heart attacks and strokes
  • Who participated: 1,704 Brazilian adults aged 45 and older who already had heart problems and were receiving care from heart specialists
  • Key finding: People who significantly improved their diet quality scores over three years had about 6% fewer heart events compared to those who didn’t improve their diets
  • What it means for you: If you have heart disease, making lasting changes to eat more whole foods and fewer processed foods may help prevent future heart problems—but you need to stick with it for at least a few years to see real benefits

The Research Details

This was a long-term follow-up study of people who were already part of a larger heart health program in Brazil. Researchers looked back at what 1,704 people ate at the beginning of the study and then tracked them for up to four years to see who had heart attacks or strokes. They measured diet quality in six different ways, including counting how many vegetables and fruits people ate, how much processed food they consumed, and how many antioxidants (healthy plant compounds) were in their diet. The researchers used a special computer system to track which participants had new heart problems during the study.

The study combined people from both the treatment and control groups of the original program, giving them a larger group to analyze. They looked at changes in diet quality at different time points—after one year, two years, and three years—to see when diet improvements started to make a difference in heart health. This approach helped them understand whether diet changes needed time to show benefits.

This research approach is important because it follows real people with actual heart disease over a long period, rather than just measuring what they eat in a lab. It also tests multiple ways of measuring diet quality, which helps researchers understand which eating patterns matter most. By tracking people for years, the study can show whether diet changes actually prevent serious health events like heart attacks and strokes.

This study has several strengths: it followed a large group of people for several years, used a reliable system to confirm heart events, and adjusted results for other factors that affect heart health like age and exercise. However, the study only included Brazilian participants, so results might be different in other populations. The study also combined two different groups (treatment and control), which could affect how we interpret the findings. Additionally, not all participants completed the full four-year follow-up, which is typical but means some data was missing.

What the Results Show

The most important finding was that people who improved their diet quality score (called the mAHEI) over three years had fewer heart events. Specifically, for every point increase in their diet quality score, the risk of having a heart attack or stroke dropped by about 6%. This benefit was seen both when researchers looked at the raw data and when they adjusted for other health factors.

However, the other five diet measurement methods tested in the study—including measures of inflammation in the diet, antioxidant content, and plant-based eating patterns—did not show clear benefits for preventing heart events. This was surprising to the researchers and suggests that different ways of measuring diet quality may capture different aspects of healthy eating.

Over the entire study period of about 3.25 years, there were 162 new cases of heart disease among the 1,704 participants. This means about 9% of the group experienced a heart attack or stroke during the study. The fact that diet improvements took three years to show benefits is an important finding—it suggests that eating well needs to be a long-term commitment, not a short-term fix.

When researchers looked at shorter time periods (one year and two years), they didn’t see clear benefits from diet improvements. This suggests that the heart-protective effects of better eating take time to develop. The study also found that the benefits were consistent whether researchers looked at men and women separately or different age groups, suggesting the findings apply broadly to people with heart disease.

Previous research has shown that healthy eating patterns can help prevent heart disease in people without existing heart problems. This study adds important new information by showing that even people who already have heart disease can benefit from improving their diet—but it takes longer than previously thought. The finding that one specific diet quality measure (mAHEI) worked better than others suggests that future research should focus on which specific eating patterns matter most for people with existing heart disease.

The study only included people from Brazil who were already receiving heart care, so the results might not apply to people in other countries or those who haven’t been diagnosed with heart disease. Some participants dropped out during the four-year study, which means the final group was smaller than the starting group. The study measured diet quality using questionnaires about what people remembered eating, which can be less accurate than other methods. Additionally, the researchers couldn’t prove that diet changes directly caused the reduction in heart events—other lifestyle changes or medications might have played a role.

The Bottom Line

If you have heart disease, focus on improving your overall diet quality by eating more whole foods, vegetables, fruits, and whole grains while reducing processed foods. This appears to help prevent future heart problems, but you should expect to maintain these changes for at least three years to see real benefits. Work with your doctor or a dietitian to create a personalized eating plan. This recommendation has moderate confidence based on this study, and should be combined with other heart-healthy habits like exercise and taking prescribed medications.

This research is most relevant for people who have already been diagnosed with heart disease or who are at high risk for heart problems. If you have had a heart attack, stroke, or have been told you have heart disease, improving your diet quality may help prevent future events. People without heart disease should also eat well for prevention, though this study doesn’t directly address that group. If you have other serious health conditions, talk to your doctor before making major diet changes.

Based on this research, you should expect to follow a healthier eating pattern for at least 2-3 years before seeing significant benefits in terms of preventing heart events. However, you may notice other improvements sooner, such as better energy levels, improved cholesterol numbers, or weight loss. Don’t get discouraged if you don’t see dramatic changes in the first few months—the real benefits appear to build up over time.

Want to Apply This Research?

  • Track your daily diet quality score by logging meals and calculating a weekly average. Specifically, count servings of vegetables, fruits, whole grains, and processed foods. Aim to increase your score by 10-15% every three months and monitor this trend over a full year to see progress.
  • Use the app to set a goal of adding one new whole food to your diet each week while removing one processed food. For example, replace sugary breakfast cereal with oatmeal, or swap soda for water. Log these swaps daily to build awareness and maintain consistency.
  • Create a long-term tracking dashboard that shows your diet quality improvements over months and years. Include quarterly check-ins where you review your progress, celebrate improvements, and adjust goals. Connect with your doctor or dietitian through the app to share your progress and get feedback on whether your diet changes are helping your heart health.

This research suggests that improving diet quality may help people with existing heart disease prevent future heart events, but it is not a substitute for medical treatment. If you have heart disease, continue taking all prescribed medications and follow your doctor’s recommendations. Before making significant changes to your diet, especially if you take blood thinners or have other health conditions, consult with your healthcare provider or a registered dietitian. This study was conducted in Brazil and results may vary in other populations. Individual results depend on many factors including genetics, exercise, stress, and overall lifestyle.