A Mediterranean diet rich in virgin olive oil may
enhance the cardioprotective benefits of high-density lipoproteins (HDL -- the
"good" cholesterol) compared to other diets, according to new
research in the American Heart Association's journal Circulation.
High levels of low-density lipoproteins (LDL -- the
"bad cholesterol") and triglycerides, a type of blood fat, are
associated with an increased risk of heart and blood vessel diseases. HDL
cholesterol is associated with a lower risk because these lipoproteins help
eliminate the excess cholesterol from the bloodstream.
"However, studies have shown that HDL doesn't
work as well in people at high risk for heart attacks, strokes and other
cardiovascular diseases, and that the functional ability of HDL matters as much
as its quantity," said senior study author Montserrat Fitó, M.D., Ph.D.,
and coordinator of the Cardiovascular Risk and Nutrition Research Group at the
Hospital del Mar Medical Research Institute in Barcelona and at the Ciber of
Physipathology of Obesity and Nutrition (CIBEROBN), Spain. "At the same
time, small-scale trials have shown that consuming antioxidant-rich foods like
virgin olive oil, tomatoes and berries improved HDL function in humans. We
wanted to test those findings in a larger, controlled study."
Researchers randomly selected 296 people at high
risk of cardiovascular disease participating in the PREDIMED (PREvención con
DIeta MEDiterránea) study. Blood samples were taken from the participants at
the beginning of the study and again at the end. Participants, average age 66,
were randomly assigned to one of three diets for a year: a traditional
Mediterranean diet enriched with virgin olive oil (about 4 tablespoons) each
day, a traditional Mediterranean diet enriched with extra nuts (about a
fistful) each day, or a healthy "control" diet that reduced
consumption of red meat, processed food, high-fat dairy products and sweets. In
addition to emphasizing fruit, vegetables, legumes, such as beans, chickpeas
and lentils, and whole grains, both Mediterranean diets included moderate
amounts of fish and poultry.
The study found that only the control diet reduced
total and LDL cholesterol levels. None of the diets increased HDL levels
significantly, but the Mediterranean diets did improve HDL function. The
improvement in HDL function was much larger among those consuming an extra
quantity of virgin olive oil.
Fitó and her team found that the Mediterranean diet
enriched with virgin olive oil improved key HDL functions, including:
Reverse cholesterol transport, the process by which
HDL removes cholesterol from plaque in the arteries and transports it to the
liver where it is used to produce hormonal compounds or eliminated from the
body.
Antioxidant protection, the ability of HDL to
counteract the oxidation of LDL, which has been found to trigger the
development of plaque in the arteries.
Vasodilator capacity, which relaxes blood vessels,
keeping them open and blood flowing.
Researchers said they were surprised to find that
the control diet, which like the Mediterranean diets was rich in fruits and
vegetables, had a negative impact on HDL's anti-inflammatory properties. A
decrease in HDL's anti-inflammatory capability is associated with
cardiovascular disease. Participants on the Mediterranean diets did not
experience a decline in this important HDL function, the authors wrote.
Researchers said the differences in results between
the diets were relatively small because the modifications of the Mediterranean
diets were modest and the control diet was a healthy one. They added that study
results are mainly focused on a high cardiovascular risk population that
includes people who can obtain the most benefits from this diet intervention.
Still, Fitó said, "following a Mediterranean
diet rich in virgin olive oil could protect our cardiovascular health in
several ways, including making our 'good cholesterol' work in a more complete
way."
Story Source:
Materials provided by American Heart Association.
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