Remarkable Heart Benefits From
Canola Oil
For: Wellness Made Easy, February 2002
The debate continues about what exactly the "Mediterranean
diet" is and why it might help prevent heart attacks. Is it
the red wine, as that famous segment on 60
Minutes suggested? Olive oil? High intake of fruits and vegetables?
Or perhaps something else about the life-style, such as moderate
serving sizes or vigorous daily activities? A recent study from
Lyon, France, has shifted the focus to another, surprising element
in the diet of some Mediterranean lands, something Morley Safer
probably never heard of—a polyunsaturated fatty acid called
alpha-linolenic acid.
This news comes from the final report of the Lyon
Diet Heart Study, published in the journal Circulation
in February. The 600 men and women (average age 53, all having had
a heart attack in the six months before the study began) were divided
into two groups. The "control" group continued to eat
a diet typical of that part of France (33% of daily calories came
from fat, and 12% from saturated fat), which was healthier than
the average American diet, though fairly rich in butter, cream,
and sausages. The "experimental" group ate more fruit,
vegetables, bread, chicken, and fish; they also ate less cheese
and much less meat, ham, and sausage (still, 30% of their daily
calories came from fat, but only 8% from saturated fat). Probably
most important, they were told to eat a margarine made from canola
(rapeseed) oil instead of butter and cream, whenever possible.
Canola oil is nutritionally similar to olive oil, except that it
is much richer in alpha-linolenic acid. Both groups consumed similar
amounts of wine.
Over the course of nearly
four years, this diet cut the risk of a second heart attack—and
the overall death rate—by as much as 70%. The researchers
attributed this to the change in fats in the diet, largely due to
the canola-oil margarine. It's impressive that a cardio-protective
effect was seen starting after only about two months. And it's likely
that this diet would also cut the risk of a first heart attack.
Why canola oil?
The study gave canola oil such a central role for
good reason. It's well known that the people living on the Greek
island of Crete have in recent decades had one of the lowest rates
of heart attacks in the world and thus a long life expectancy. It's
also known that Cretans had a very healthy diet, rich in fruits,
vegetables, and bread and low in meat. And, interestingly, blood
tests revealed that they consumed lots of alpha-linolenic acid,
probably from walnuts and the leafy green called purslane. As the
Cretans have prospered in recent years, however, their diet has
become less healthful and their life-style has changed—and
their rate of heart disease has risen dramatically. The Japanese,
who also have a very low rate of heart disease, have a high intake
of alpha-linolenic acid, too, but they get it from soy and canola
oils.
Alpha-linolenic acid is a "short-chain"
omega-3 fatty acid, related to the longer-chain omega-3s found in
fish. Not many foods are rich in alpha-linolenic acid—only
canola, soybean, and flaxseed oils, along with purslane, walnuts,
and a few other foods. (An article on flaxseed will appear in an
upcoming issue of the WELLNESS LETTER.) Omega-3s may help protect
the heart in several ways. For instance, they are believed to reduce
the risk of blood clotting and potentially deadly heart rhythm abnormalities,
and may also have an anti-inflammatory effect in blood vessels.
This is not to say that canola oil or alpha-linolenic acid is a magic bullet against heart attacks. Remember, the people in this study also had a diet rich in fruits, vegetables, beans, and whole grains, which are good sources of vitamins, minerals, and other protective plant compounds. Their intake of saturated fat (primarily from meat and other animal products) was low, as was their intake of other polyunsaturated fatty acids (notably linoleic acid, found in other vegetable oils).
The bottom line: Most
Americans need to eat not only less fat, but different fats. The
most important thing is to limit your intake of saturated fat, which
means your diet should be semi-vegetarian or vegetarian. In addition,
based on this new research, we now suggest that you consume more
alpha-linolenic acid. No one knows precisely how much of it is needed
to reduce the risk of heart disease. Simply consume some canola
or soybean oil occasionally, as well as some flaxseed and walnuts,
if you like.
UC Berkeley Wellness Letter, May 1999
