Researchers tested whether olive oil and certain animal fats could help reverse heart disease in rats fed an unhealthy diet. After 12 weeks of eating a diet designed to cause heart problems, rats received either olive oil, sheep fat, cow fat, or a heart medication. All three oils and fats significantly improved cholesterol levels, reduced harmful inflammation, and helped repair damage to heart tissue. Olive oil showed the strongest benefits. These findings suggest that the type of fat we eat—not just the amount—might play an important role in protecting our hearts from disease.

The Quick Take

  • What they studied: Whether olive oil and certain animal fats could help reverse heart disease caused by eating an unhealthy, high-fat diet
  • Who participated: Male rats that were fed a diet designed to cause heart disease and high cholesterol, then treated with different oils and fats for 12 weeks
  • Key finding: All three oils and fats—olive oil, sheep fat, and cow fat—significantly lowered bad cholesterol, raised good cholesterol, reduced inflammation, and helped repair heart damage. Olive oil worked best, followed by sheep fat and cow fat.
  • What it means for you: This suggests that certain fats might help protect your heart, but remember: this was tested in rats, not humans. The type of fat you eat may matter more than you think. Talk to your doctor before making big changes to your diet.

The Research Details

Scientists created heart disease in rats by feeding them a special diet high in cholesterol and unhealthy ingredients for 12 weeks. Then they divided the sick rats into groups and gave each group a different treatment: olive oil, sheep fat, cow fat, or a common heart medication (simvastatin). They continued this treatment for another 12 weeks while measuring changes in the rats’ blood and heart tissue.

The researchers measured several important markers: cholesterol levels (both the bad kind and good kind), inflammation markers, and damage to heart tissue. They also looked at the actual heart tissue under a microscope to see if the damage was healing. This approach allowed them to test whether these oils could not just prevent heart disease, but actually reverse damage that had already happened.

The study focused on the specific fatty acids in each oil—the building blocks that make up fats. Olive oil is high in oleic acid, while the animal fats contained more stearic acid. Understanding these differences helped explain why each oil worked the way it did.

This research approach is important because it tests whether these oils can actually reverse existing heart disease, not just prevent it from getting worse. By looking at both blood markers and actual tissue damage, the researchers could see the complete picture of how these oils affect the heart. Testing in rats first helps scientists understand if these treatments might work in humans before doing expensive and time-consuming human studies.

This study was published in Scientific Reports, a well-respected scientific journal. The researchers used multiple ways to measure results (blood tests and tissue examination), which makes the findings more reliable. However, this was an animal study, so results may not directly apply to humans. The study didn’t specify exactly how many rats were used, which would help readers understand the strength of the findings. Animal studies are important first steps, but human studies are needed to confirm these results work in people.

What the Results Show

The rats that ate an unhealthy diet developed high cholesterol, inflammation, and heart damage—similar to heart disease in humans. When treated with olive oil, sheep fat, or cow fat, these rats showed dramatic improvements. Bad cholesterol (LDL) dropped significantly, good cholesterol (HDL) increased, and markers of inflammation and oxidative stress (cellular damage) decreased substantially.

When researchers looked at the actual heart tissue under a microscope, they saw that the fatty buildup in the arteries—the hallmark of heart disease—had partially or completely reversed in the treated rats. This is remarkable because it suggests these oils don’t just stop heart disease from getting worse; they may actually help repair existing damage.

Olive oil produced the strongest healing effects, followed by sheep fat and then cow fat. Interestingly, all three oils worked almost as well as simvastatin, a powerful prescription medication commonly used to treat high cholesterol. The researchers believe the different fatty acids in each oil—oleic acid in olive oil and stearic acid in animal fats—explain why they all helped but in slightly different ways.

The study measured oxidative stress (cellular damage from harmful molecules) and found that all three oils reduced this damage significantly. They also measured C-reactive protein, a marker of inflammation in the body, and found it decreased in all treated groups. These secondary findings are important because inflammation and oxidative stress are major drivers of heart disease progression. The fact that these oils reduced both suggests they work through multiple protective mechanisms, not just by lowering cholesterol.

Previous research has shown that olive oil is heart-healthy, which this study confirms. However, this research is unusual because it also tested animal fats (tallow) and found they had protective effects too. This challenges the common belief that all animal fats are bad for your heart. The key finding is that the specific type of fat matters—the fatty acid composition determines whether a fat helps or hurts your heart. This aligns with emerging nutrition science suggesting that not all saturated fats affect the body the same way.

This study was conducted in rats, not humans, so we cannot be certain the results will apply to people. Rats’ bodies process food differently than human bodies do. The study didn’t specify the exact number of rats used, making it harder to judge how reliable the results are. The study also didn’t test these oils in combination with other treatments or in different doses, so we don’t know the optimal amount to use. Finally, this was a short-term study (24 weeks total), so we don’t know if the benefits would last longer or if any problems might develop over time.

The Bottom Line

Based on this research, olive oil appears to be a heart-protective food choice (moderate confidence, since this is animal research). The findings suggest that eating foods rich in oleic acid—like olive oil, avocados, and certain nuts—may help protect your heart. However, this single rat study is not enough to change medical recommendations. If you have high cholesterol or heart disease, continue taking prescribed medications and follow your doctor’s advice. You can discuss adding olive oil to your diet as part of a heart-healthy eating plan, but don’t use it as a replacement for medication.

People with high cholesterol, heart disease, or family history of heart problems should find this interesting. People trying to prevent heart disease may also benefit from knowing that olive oil appears protective. However, this research doesn’t apply to people with specific allergies or medical conditions that restrict fat intake—talk to your doctor first. This research is preliminary, so it shouldn’t change anyone’s current medical treatment without doctor approval.

In the rat study, improvements in cholesterol and inflammation appeared within 12 weeks of treatment. In humans, changes typically take longer—usually 4-8 weeks to see improvements in cholesterol levels, and months to years to see reversal of existing heart disease. Don’t expect overnight results; heart health is a long-term commitment.

Want to Apply This Research?

  • Track daily olive oil consumption (in tablespoons) and weekly cholesterol or inflammation markers if you have access to blood tests. Set a goal of 1-2 tablespoons of olive oil daily as part of meals.
  • Replace cooking oils with olive oil for salad dressings and low-heat cooking. Add olive oil to meals you already eat rather than trying to add new foods. Start with one meal per day and gradually increase.
  • Check in monthly on how consistently you’re using olive oil. If possible, get cholesterol levels tested every 3-6 months to see if dietary changes are helping. Track any changes in energy levels or how you feel overall.

This research was conducted in rats and has not been tested in humans. These findings should not replace medical advice or prescribed heart medications. Before making significant dietary changes, especially if you have high cholesterol, heart disease, or take medications, consult with your doctor or a registered dietitian. This study is preliminary and represents one piece of evidence; more human research is needed to confirm these results apply to people. Always follow your healthcare provider’s recommendations for managing heart health.