"PREDIMED: Does Eating Nuts Prevent Strokes?"
The Lyon Diet Heart Trial showed that a Mediterranean-type diet
could significantly reduce the risk of having a second heart attack,
but since many first heart attacks are fatal,
better to prevent heart attacks in the first place.
But no randomized trial had ever been conducted
to test the Mediterranean diet for this so-called 'primary prevention' until now.
The PREDIMED study, from the Spanish PREvención con DIeta MEDiterránea,
in which a whopping 7,447 patients were randomized into three groups.
These were folks at high risk for a heart attack.
About half were obese, diabetic,
most had high blood pressure, high cholesterol,
but had not yet had their first heart attack or stroke.
A third were told to eat a Mediterranean diet
and given a free quart of extra virgin olive oil every week.
The second group was told to eat a Mediterranean diet
and given a half pound of free nuts every week,
and the third group was told to follow
the American Heart Association guidelines
and reduce their fat intake.
No portion control or exercise advice was given,
and they were followed for about five years.
The results were published in the prestigious
New England Journal of Medicine.
Now the first thing you do when you look at a diet intervention trial is
you see what the groups actually ended up eating,
which is often very different from what they were told to eat.
For example, the so-called low fat group started out at 39% of calories from fat,
and ended up getting 37% of calories from fat,
which is high fat even compared
to the Standard American Diet, which comes in at 33%,
something the researchers plainly acknowledged.
In fact the control group didn't change their diets much at all over the years,
so it can be thought of as the what-if-you-don't-do-anything group,
which is still an important control group to have,
though the two Mediterranean diet groups didn't get much more Mediterranean.
They were told to eat more fruits and vegetables,
for example, less meat and dairy,
but didn't accomplish either of those goals compared to control.
The biggest changes reported were, not surprisingly,
in the consumption of the freebies.
The group that got a free jug of extra-virgin olive oil
delivered to their home every week really did start increasing their consumption,
in part by replacing some of the refined olive oil
they had been using, but of course would have to pay for.
And those that got a half pound of free nuts sent to them
every week for four years straight did start eating more nuts.
Too bad they couldn't have slipped a little free broccoli in there, too.
So basically they designed a study to test two different Mediterranean diets
versus a low fat diet, but ended up studying something very different.
In essence what happens when thousands of people switch
from consuming about three tablespoons of olive oil a day, half virgin,
to four tablespoons of all virgin, compared to thousands of people
who all the sudden go from eating about a half an ounce of nuts a day to a whole ounce,
compared to thousands of people who don't make much of a change at all.
It may not have been what they were hoping for,
but these are important research questions in and of themselves.
Let's say you're at high risk for heart disease, eating like this.
What would happen if you started to add
like an extra half-ounce of nuts to your daily diet,
or more unrefined olive oil?
We didn't know until now.
With no significant differences in meat and dairy intake,
there were no significant differences in saturated fat or cholesterol intake.
So no surprise: no significant differences in their blood cholesterol levels,
and so no difference significantly in their subsequent number of heart attacks.
In the five or so years the study ran, there were 37 heart attacks
in the olive oil group,
31 in the nut group, and 38 in the neither group.
No significant difference.
Same with dying from a heart attack or stroke, or dying from any cause.
But those in the olive oil, and especially the nut group, had significantly fewer strokes.
All three groups were eating stroke-promoting diets;
I mean, they all had strokes in them after eating these diet for years,
and so ideally, you know, we'd choose diets that can stop or reverse the disease process,
but the diet with added extra virgin olive oil caused about a third fewer strokes,
and adding nuts seemed to cut their stroke risk nearly in half.
If this worked as well in the general population,
in the U.S. alone that would mean preventing 89,000 strokes a year.
That would be like ten strokes an hour around the clock,
prevented by simply adding half an ounce of nuts to one's daily diet.