According to Gram Research analysis, people with heart disease who show high levels of harmful bacterial substances in their blood after eating have a 42% higher risk of experiencing another heart event within 7 years. A Mediterranean diet—rich in vegetables, fish, and olive oil—reduced this risk more effectively than a low-fat diet, suggesting that the type of food you eat influences how your gut responds to meals and affects heart health.
Researchers studied 1,002 people with heart disease to understand how their bodies react to food. They discovered that when certain harmful bacterial substances enter the bloodstream after eating, it’s linked to future heart problems. The good news? A Mediterranean diet—rich in vegetables, fish, and olive oil—was better at preventing this harmful reaction than a low-fat diet. This finding suggests doctors might one day use simple blood tests after meals to help predict and prevent heart disease in people who’ve already had heart problems.
Key Statistics
A 2026 randomized controlled trial of 1,002 people with heart disease found that those with higher postprandial endotoxemia (harmful bacterial substances in blood after eating) had a 42% increased risk of major cardiovascular events over 7 years.
In the same CORDIOPREV study, people eating a low-fat diet with moderate increases in postprandial endotoxemia had a 45% higher risk of heart problems compared to those following a Mediterranean diet.
Both the low-fat and Mediterranean diets reduced harmful bacterial substance levels over time, but the Mediterranean diet created a gut bacterial profile more strongly associated with preventing these harmful substances from entering the bloodstream.
The Quick Take
- What they studied: Whether the body’s reaction to food—specifically harmful bacterial substances that leak into the blood after eating—can predict future heart problems in people with existing heart disease.
- Who participated: 1,002 adults with coronary heart disease (existing heart problems) who were randomly assigned to eat either a low-fat diet or a Mediterranean diet for 7 years.
- Key finding: People whose blood showed higher levels of harmful bacterial substances after eating had a 42% higher risk of experiencing another heart event within 7 years. The Mediterranean diet reduced this risk more effectively than the low-fat diet.
- What it means for you: If you have heart disease, the type of diet you eat matters for preventing future problems. A Mediterranean diet appears to be more protective than simply eating low-fat foods. Talk to your doctor about dietary changes, especially if you’re at risk for heart disease.
The Research Details
This was a large, carefully controlled study called the CORDIOPREV trial. Researchers followed 1,002 people with heart disease for 7 years, randomly assigning them to eat either a low-fat diet or a Mediterranean diet. At the start and after 3 years, participants ate a test meal, and researchers measured how much of a harmful bacterial substance (called LPS) entered their bloodstream after eating. The researchers also analyzed the bacteria living in participants’ digestive systems to understand how diet changes the gut environment.
The study tracked whether participants experienced major heart problems (like heart attacks or strokes) during the 7-year period. Researchers used statistical analysis to determine if the amount of bacterial substance in the blood after eating could predict who would have heart problems later.
This approach is valuable because it looks at what happens in real time when people eat—not just what they eat—and connects it to actual health outcomes over many years.
Most research on heart disease focuses on cholesterol or blood pressure, but this study examines a different mechanism: how food affects the barrier in your gut, allowing harmful bacterial substances to leak into the bloodstream. This ’leaky gut’ response may be a hidden risk factor that doctors currently don’t measure. Understanding this connection could lead to better ways to predict and prevent heart disease in people who’ve already had problems.
This study is highly reliable because it’s a randomized controlled trial—the gold standard in medical research. It involved over 1,000 participants followed for 7 years, which is a long time and large group. The researchers measured actual health outcomes (heart attacks and strokes), not just blood markers. However, the study measured LPS levels at only two time points, so we don’t know if the pattern stayed consistent throughout the 7 years. The study was published in a peer-reviewed medical journal, meaning other experts reviewed the methods before publication.
What the Results Show
The main discovery was striking: people whose blood showed a larger increase in harmful bacterial substances (LPS) after eating at the beginning of the study were 42% more likely to experience a major heart event (heart attack, stroke, or cardiac death) over the next 7 years. This association held true even after researchers accounted for other known heart disease risk factors.
When researchers compared the two diets, they found that people eating a low-fat diet who had moderate increases in LPS after meals had a 45% higher risk of heart problems compared to people eating a Mediterranean diet. This suggests the Mediterranean diet provided extra protection beyond just reducing overall fat intake.
Both diets reduced LPS levels over time and changed the composition of gut bacteria in ways associated with lower LPS responses. However, the Mediterranean diet appeared to create a more favorable gut environment. The study suggests that the type of food matters—not just the amount of fat—in determining how your gut responds to meals.
The research showed that gut bacteria composition changed differently depending on which diet people followed. The Mediterranean diet created a gut bacterial profile that was better at preventing harmful bacterial substances from entering the bloodstream. This finding is important because it suggests the Mediterranean diet works partly by improving gut health, not just by being lower in fat. The study also found that the protective effect of the Mediterranean diet was consistent across different groups of participants, suggesting it may work for many people with heart disease.
Previous research has shown that ’leaky gut’—where harmful substances cross from the digestive system into the bloodstream—is linked to inflammation and heart disease. This study is one of the first to show that measuring this leakage after eating can predict future heart problems in people who already have heart disease. Earlier studies suggested the Mediterranean diet is heart-healthy, but this research provides a new explanation for why: it may work by keeping the gut barrier stronger and preventing harmful bacterial substances from entering the blood.
The study measured LPS levels at only the beginning and after 3 years, so researchers couldn’t track how levels changed throughout the 7 years. The study included mostly people of European descent, so results may not apply equally to other populations. Researchers couldn’t determine whether the LPS increase directly caused heart problems or was simply a marker of other underlying issues. The study measured LPS using a specific lab test that may not capture all types of harmful bacterial substances. Finally, people in the study knew which diet they were assigned to, which could have influenced their behavior or how carefully they followed the diet.
The Bottom Line
If you have heart disease or are at high risk, consider adopting a Mediterranean diet (emphasizing vegetables, fruits, whole grains, fish, and olive oil) rather than simply eating a low-fat diet. This diet appears to reduce harmful bacterial substances in your blood after eating and may lower your risk of future heart problems. Discuss dietary changes with your doctor or a registered dietitian. The evidence for this specific benefit is moderate to strong based on this large, long-term study.
This research is most relevant to people who have already experienced heart disease or have significant risk factors. If you’ve had a heart attack, stroke, or been diagnosed with coronary heart disease, these findings apply to you. The results may also be relevant to people with multiple heart disease risk factors (high cholesterol, high blood pressure, diabetes, or family history). If you’re generally healthy with no heart disease history, the Mediterranean diet is still a healthy choice, but this specific research doesn’t directly address your situation.
The study followed people for 7 years, so benefits likely develop over months to years, not days or weeks. You might expect to see improvements in blood markers (like LPS levels) within weeks to months of dietary changes, but protection against future heart events takes longer to develop. Stick with dietary changes for at least several months before expecting major health improvements.
Frequently Asked Questions
Can what I eat after meals affect my heart disease risk?
Yes. Research shows that how your body reacts to food—specifically whether harmful bacterial substances leak into your blood after eating—is linked to future heart problems. A Mediterranean diet appears to reduce this harmful reaction better than a low-fat diet.
Is the Mediterranean diet better than a low-fat diet for heart disease?
For people with existing heart disease, this study found the Mediterranean diet provided better protection against future heart events. People on a low-fat diet with certain gut responses had 45% higher risk of heart problems compared to those on a Mediterranean diet.
How long does it take for diet changes to protect my heart?
This study followed people for 7 years, suggesting benefits develop over months to years. Blood markers may improve within weeks to months, but protection against future heart events takes longer—likely several months to years of consistent dietary changes.
What exactly is a Mediterranean diet and why does it help?
A Mediterranean diet emphasizes vegetables, fruits, whole grains, fish, and olive oil. Research suggests it works by improving gut health and preventing harmful bacterial substances from entering your bloodstream, which reduces inflammation and heart disease risk.
Should I get tested for this bacterial substance in my blood?
This study suggests measuring postprandial endotoxemia could help predict heart disease risk, but this test isn’t yet standard medical practice. Discuss with your cardiologist whether this testing might be useful for your specific situation.
Want to Apply This Research?
- Track daily adherence to Mediterranean diet components: servings of vegetables, fruits, whole grains, fish, and olive oil consumption. Set a goal of 5+ servings of vegetables/fruits daily and fish 2-3 times weekly. Log these specific foods to monitor consistency over weeks and months.
- Use the app to build a Mediterranean diet meal plan with specific recipes and shopping lists. Set reminders for meal prep on weekends. Track which Mediterranean foods you enjoy most to increase adherence. Create a ‘favorite Mediterranean meals’ list to rotate through regularly.
- Monitor weekly diet adherence scores and monthly trends. Track any symptoms or health markers your doctor measures (like cholesterol or blood pressure) to see if dietary changes correlate with improvements. Set quarterly check-ins to assess how well you’re maintaining the diet and adjust recipes or strategies if needed.
This research provides important insights for people with existing heart disease, but it should not replace personalized medical advice from your doctor or cardiologist. The study measured associations between blood markers and heart disease risk, but cannot prove that the bacterial substances directly cause heart problems. Before making significant dietary changes, especially if you take medications or have other health conditions, consult with your healthcare provider or a registered dietitian. This information is for educational purposes and should not be used for self-diagnosis or self-treatment of heart disease.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.