Scientists at the University of Florida, USA, have conducted a randomized crossover trial to investigate the cardiometabolic effects of extra virgin olive oil within a whole-food, plant-based vegan diet.
The trial report is published in the Journal of the American Heart Association.
Study: Recipe for Heart Health: A Randomized Crossover Trial on Cardiometabolic Effects of Extra Virgin Olive Oil Within a Whole‐Food Plant‐Based Vegan Diet. Image Credit: luigi giordano / Shutterstock
Background
An unhealthy lifestyle, including poor dietary habits and physical inactivity, is a leading cause of cardiometabolic diseases worldwide. Plant-based diets, including Mediterranean and vegetarian or vegan diets, have shown promising outcomes in cardiometabolic risk reduction. Both dietary patterns focus on reducing saturated fats and increasing the intake of fruits, vegetables, and whole grains.
Low-fat, whole-food, plant-based diets primarily include whole-food and unrefined food products and restrict heavily processed products, refined grains, added sugar, and oils. Similar to vegan diets, this dietary pattern often excludes animal-based foods and recommends restricting vegetable oil fat intake to less than 10% to 15% of energy intake.
Mediterranean diet also focuses on consuming plant-based foods. However, this diet recommends extra virgin olive oil (EVOO) as the primary source of dietary fat, with moderate consumption of seafood, poultry, and dairy products and low intake of red meat and animal‐derived fats. Dietary fat intake from vegetable oils can be up to 35% to 40% of energy intake in the Mediterranean diet.
To compare the cardiometabolic effects of extra virgin oil within a low-fat, whole-food, plant-based diet, scientists at the University of Florida have designed a randomized crossover trial named “The Recipe for Heart Health trial.”
Study design
The study recruited 40 adults aged 18 to 79 with a 5% or higher cardiovascular disease risk. They were randomly assigned to follow one of two whole-food, plant-based dietary patterns for four weeks.
One dietary pattern included four tablespoons of uncooked extra virgin olive oil per day (high-EVOO diet), and the other included less than one teaspoon per day (low-EVOO diet). The participants alternatively followed these two dietary patterns for four weeks, with a washout period of one week in between.
Participants received weekly virtual group culinary medicine classes led by a dietitian/chef to support dietary adherence. Participant’s age, sex, and body weight changes were considered in the analysis as covariates to determine the effects of two dietary patterns on low-density lipoprotein-cholesterol (LDL-C) and other cardiometabolic markers, including blood lipids, glycemic measures, and inflammatory mediators.
Important observations
The measurement of blood metabolite levels after each 4-week period showed that both dietary patterns caused a significant reduction in blood LDL-C level, with no significant differences between the high-EVOO diet and low-EVOO diet.
Both dietary patterns also caused comparable reductions in total cholesterol, apolipoprotein B, high-density lipoprotein-cholesterol (HDL‐C), glucose, and high-sensitivity C-reactive protein (CRP) levels compared to baseline values.
Sensitivity analyses considering diet-sequence interactions (carryover effects) revealed that the low-EVOO diet caused a significantly higher reduction in LDL-C level than the high-EVOO diet during the first 4-week period, which was diminished over the second 4-week period.
The low-EVOO diet also caused a significantly higher reduction in total cholesterol, HDL-C, apolipoprotein B, and glucose levels than the high-EVOO diet during the first 4-week period.
Differences in LDL-C levels between the two diets were observed depending on which diet was followed first. While the high to low EVOO diet sequence caused a significant reduction in LDL-C level, a significant increase was observed for the low to high EVOO diet sequence.
The low to high EVOO diet sequence also caused a significant increase in total cholesterol, HDL-C, and glucose levels.
Regarding anthropometric measurements, both dietary patterns caused a significant reduction in body weight. However, the reduction was significantly more pronounced during the low-EVOO diet period.
Study significance
The study findings reveal that both high-level and low-level EVOO intake is associated with a reduction in blood LDL-C levels, despite total fat intake comprising 48% and 32% of total energy during the high and low EVOO diet periods, respectively.
The low-EVOO diet used in the study has shown higher efficacy in reducing LDL-C levels than the high-EVOO diet. The study findings also highlight that the addition of EVOO after following a low intake may impede further reduction in LDL-C levels.
Saturated fatty acids are known to downregulate hepatic LDL receptor activity, which induces circulating LDL-C levels. The intake of saturated fat during the high-EVOO diet period was slightly higher than that during the low-EVOO period. This could be a reason behind the observed difference in LDL-C levels between high- and low-EVOO diets.
Furthermore, during the low-EVOO diet period, unrefined whole plant‐based fats, such as avocados, nuts, seeds, and olives, comprised most of the dietary fat. This type of dietary fat retains inherent dietary fiber and intact phytochemicals, known to have cholesterol-lowering and cardioprotective effects.
The researchers noted that although both diets improved the cardiometabolic risk profiles, the low-EVOO diet had a more pronounced effect on reducing LDL-C levels, particularly when followed first. As mentioned by the scientists, future studies are required to determine the long-term cardiometabolic benefits of low-EVOO dietary interventions.
Overall, the study indicates that a whole-food, plant-based diet with low-level EVOO might be beneficial for improving cardiometabolic health in adult individuals at risk of developing cardiovascular disease.
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