[Heart disease experts
said the study was a triumph because it showed that a diet is powerful in
reducing heart disease risk, and it did so using the most rigorous methods.
Scientists randomly assigned 7,447 people in Spain who were overweight, were
smokers, had diabetes or other risk factors for heart disease to follow the Mediterranean
diet or a low-fat one.]
By Gina Kolata
About
30 percent of heart attacks, strokes and deaths from heart disease can be
prevented in people at high risk if they switch to a Mediterranean diet rich in
olive oil, nuts, beans, fish, fruits and vegetables, and even drink wine with
meals, a large and rigorous new study found.
The
findings, published on the New England Journal of Medicine’s Web site on
Monday, were based on the first major clinical trial to measure the diet’s
effect on heart risks. The magnitude of the diet’s benefits startled experts.
The study ended early, after almost five years, because the results were so
clear it was considered unethical to continue.
The
diet helped those following it even though they did not lose weight and most of
them were already taking statins, or blood pressure or diabetes drugs
to lower their heart disease risk.
“Really
impressive,” said Rachel Johnson, a professor of nutrition at the University of
Vermont and a spokeswoman for the American Heart Association. “And the really
important thing — the coolest thing — is that they used very meaningful end
points. They did not look at risk factors like cholesterol of hypertension or
weight. They looked at heart attacks and strokes and death. At the end of the
day, that is what really matters.”
Until
now, evidence that the Mediterranean diet reduced the risk of heart disease was
weak, based mostly on studies showing that people from Mediterranean countries
seemed to have lower rates of heart disease — a pattern that could have been
attributed to factors other than diet.
And
some experts had been skeptical that the effect of diet could be detected, if
it existed at all, because so many people are already taking powerful drugs to
reduce heart disease risk, while other experts hesitated to recommend the diet
to people who already had weight problems, since oils and nuts have a lot of
calories.
Heart disease experts
said the study was a triumph because it showed that a diet is powerful in
reducing heart disease risk, and it did so using the most rigorous methods.
Scientists randomly assigned 7,447 people in Spain who were overweight, were
smokers, had diabetes or other risk factors for heart disease to follow the Mediterranean
diet or a low-fat one.
Low-fat
diets have not been shown in any rigorous way to be helpful, and they are also
very hard for patients to maintain — a reality born out in the new study, said
Dr. Steven E. Nissen, chairman of the department of cardiovascular medicine at
the Cleveland Clinic Foundation.
“Now
along comes this group and does a gigantic study in Spain that says you can eat
a nicely balanced diet with
fruits and vegetables and olive oil and lower heart disease by 30 percent,” he
said. “And you can actually enjoy life.”
The
study, by Dr. Ramon Estruch, a professor of medicine at the University of
Barcelona, and his colleagues, was long in the planning. The investigators
traveled the world, seeking advice on how best to answer the question of
whether a diet alone could make a big difference in heart disease risk. They
visited the Harvard School of Public Health several times to consult Dr. Frank
M. Sacks, a professor of cardiovascular disease prevention there.
In
the end, they decided to randomly assign subjects at high risk of heart disease
to three groups. One would be given a low-fat diet and counseled on how to
follow it. The other two groups would be counseled to follow a Mediterranean
diet. At first the Mediterranean dieters got more intense support. They met
regularly with dietitians while the low-fat group just got an initial visit to
train them in how to adhere to the diet followed by a leaflet each year on the
diet. Then the researchers decided to add more intensive counseling for them,
too, but they still had difficulty staying with the diet.
One
group assigned to a Mediterranean diet was given extra virgin olive oil each
week and was instructed to use at least 4 tablespoons a day. The other group
got a combination of walnuts, almonds and hazelnuts and was instructed to eat
about an ounce of them each day. An ounce of walnuts, for example, is about a
quarter cup — a generous handful. The mainstays of the diet consisted of at
least 3 servings a day of fruits and at least two servings of vegetables.
Participants were to eat fish at least three times a week and legumes, which
include beans, peas and lentils, at least three times a week. They were to eat
white meat instead of red, and, for those accustomed to drinking, to have at
least 7 glasses of wine a week with meals.
They
were encouraged to avoid commercially made cookies, cakes and pastries and to
limit their consumption of dairy products and processed meats.
To
assess compliance with the Mediterranean diet, researchers measured levels of a
marker in urine of olive oil consumption — hydroxytyrosol — and a blood marker
of nut consumption — alpha-linolenic acid.
The
participants stayed with the Mediterranean diet, the investigators reported.
But those assigned to a low-fat diet did not lower their fat intake very much.
So the study wound up comparing the usual modern diet, with its regular
consumption of red meat, sodas and commercial baked goods, to a diet that
shunned all that.
Dr.
Estruch said he thought the effect of the Mediterranean diet was because of the
entire package, not just the olive oil or nuts. He did not expect, though, to
see such a big effect so soon. “This is actually really surprising to us,” he
said.
Not
everyone is convinced, though. Dr. Caldwell Blakeman Esselstyn Jr., the author
of the best-seller “Prevent and Reverse Heart Disease: The Revolutionary,
Scientifically Proven, Nutrition-Based Cure,” who promotes a vegan diet and
does not allow olive oil, dismissed the new study.
His
views and those of another promoter of a very-low-fat diet, Dr. Dean Ornish,
have influenced many to try to become vegan. Former President Bill Clinton,
interviewed on CNN, said Dr. Esselstyn’s and Dr. Ornish’s writings helped
convince him that he could reverse his heart disease in that way.
Dr.
Esselstyn said those in the Mediterranean diet study still had heart attacks
and strokes. So, he said, all the study showed was that “the Mediterranean diet
and the horrible control diet were able to create disease in people who
otherwise did not have it.”
Others
hailed the study.
“This
group is to be congratulated for carrying out a study that is nearly impossible
to do well,” said Dr. Robert H. Eckel, a professor of medicine at the
University of Colorado and a past president of the American Heart Association.
As
for the researchers, they have changed their own diets and are following a
Mediterranean one, Dr. Estruch said.
“We
have all learned,” he said.