For people at risk for heart disease, switching from an omnivorous diet to one that includes a variety of nuts, fruits, and vegetables with light dressings is a pretty surefire way to lower fat levels in the body.
However, for some people, adding a generous amount of extra virgin olive oil may undermine healthy lifestyle choices.
A team of researchers from the University of Florida and the National Institute of Diabetes and Digestive and Kidney Diseases has investigated the health benefits of a plant-based diet for people at risk of developing atherosclerotic cardiovascular disease.
More recently, with the promotion of vegan and Mediterranean-style diets, extra virgin olive oil (EVOO) has been extolled as a means of lowering worrying cholesterol levels.
The Mediterranean diet includes fats of animal origin, and when you add in the often recommended amounts of olive oil, your fat intake can reach almost half of your body’s energy intake.
Studies have shown conflicting results about the benefits of different parts of the Mediterranean diet, and there is little evidence on whether olive oil combined with a low-fat, whole-grain plant-based diet is truly beneficial for people with risk factors for heart disease.
To investigate this, the researchers recruited 40 adults aged 18 to 79 to follow a carefully constructed vegan diet for a total of eight weeks: four weeks with an extra four teaspoons of extra virgin olive oil per day, four weeks with a low-extra virgin olive oil version of the diet without the added olive oil, with a one-week break in between.
Both low and high EVOO diets improved cardiometabolic profiles (cholesterol, blood glucose, and inflammation) compared to measurements taken before the diet began. Interestingly, the order in which the diets were started led to differences in changes in cholesterol levels compared to baseline values at the start of the study.
Participants who started their diet with relatively high amounts of olive oil and then switched to a diet that contained little or no olive oil experienced a decrease in their low-density lipoprotein (LDL) or “bad” cholesterol levels.
On the other hand, slathering on EVOO after consuming little or no oil for several weeks appears to thwart LDL reduction.
The research team believes that the small amounts of saturated fat in extra virgin olive oil may affect how the liver processes LDL, leading to increased levels of LDL in the blood and increasing the risk of stroke and heart attack.
“Reduced intake of extra virgin olive oil may have a greater lipid-lowering effect than relatively higher intake,” the researchers wrote in their published paper.
A few caveats here: Although the researchers took gender and weight differences into account in their calculations, all of the participants were assessed to be at borderline-to-high risk for atherosclerotic cardiovascular disease (ASCVD), which can result from too much artery-clogging LDL cholesterol.
Additionally, the differences in relative LDL cholesterol reduction were not that great, especially with the second-low EVOO diet. These plant-based diets, with or without olive oil, were again shown to be good for you.
“Although both diets improved the metabolic phenotype, the intervention reducing EVOO intake may have superior effects on lowering LDL-C in individuals at highest risk,” the researchers wrote.
Taken together, the researchers say, people at high risk for heart disease may want to consider cutting back on their excessive olive oil intake. Future studies could examine how this association plays out in larger groups of participants over a longer period of time, but it’s another reminder that we are what we eat.
“Adding extra virgin olive oil after small amounts consumed in a whole food, plant-based diet may counteract this risk reduction,” the researchers wrote.
“Considerations regarding optimal dietary fat sources and amounts of extra virgin olive oil in a risk-reducing vegan dietary pattern may vary depending on dietary status and risk level.”
The study was published in the Journal of the American Heart Association.