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 Over time, cutting back on saturated fat was tied to a drop of up to
25 percent in heart disease risk - unless people used refined
carbohydrates like white bread or pasta as replacements. In that
case, there was no benefit.
"The saturated fats look benign when you compare them to the refined
carbohydrates, but when you compare them to something else they’re
not benign," said Adela Hruby from the Harvard T.H. Chan School of
Public Health in Boston, a coauthor of the study.
For decades, people have been told to stay away from foods high in
saturated fat, such as fatty meats, butter and cheese. Saturated fat
increases the amount of LDL or "bad" cholesterol in the blood, which
is linked to heart disease.
Currently, the American Heart Association recommends that saturated
fats comprise no more than 6 percent of a person's daily diet. The
2010 U.S. Dietary Guidelines for Americans suggest that a maximum of
10 percent of daily calories come from saturated fats.
But recent analyses of data from past studies found no link between
saturated fats and heart disease, Hruby's team writes in the Journal
of the American College of Cardiology.
And other studies have found no differences when saturated fats were
replaced by carbohydrates - but that lack of an association might be
explained by researchers not distinguishing between types of
carbohydrates, the study team believes.
Their new results are based on data from nearly 130,000 people who
were asked about their diets every four years, in studies conducted
from the 1980s to 2010. At the start, participants were free of
diabetes, cancer and heart disease. Over 24 to 30 years of
follow-up, there were about 7,500 cases of heart disease.
People who replaced 5 percent of saturated fat calories in their
diet with an equivalent amount of polyunsaturated fats - like those
in fatty fish and flax seeds - had a 25 percent decreased risk of
heart disease compared to those who didn’t.
Those who replaced 5 percent of saturated fat with monounsaturated
fats like olive or peanut oil, or whole nuts, had a 15 percent
reduced risk of heart disease.
Replacing 5 percent of saturated fat calories with an equal amount
of whole grains was tied to a 9 percent reduced risk of heart
disease.
But there was no difference in heart disease risk when people
substituted refined carbohydrates for saturated fats.
The study's main point is that it’s about the swaps people make in
their diet for saturated fats, Hruby said.
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"Use some olive oils instead of butter or eat a few handfuls of nuts
instead of a few handfuls of potato chips," she said. "These are not
complex swaps."
One limit of the study, the authors acknowledge, is that errors are
possible when people are asked to estimate what foods they ate.
Dr. Steven Nissen, chair of cardiovascular medicine at the Cleveland
Clinic, who wasn't involved in the study, doesn't think anyone
should make clinical decisions based on its results.
"As a society we need to do prospective randomized trials to answer
these questions," he said.
Nissen cited the Prevention with Mediterranean Diet (PREDIMED)
trial, which followed people who were randomly assigned to a
Mediterranean diet with added olive oil or nuts, or a low-fat diet.
Those on the Mediterranean diet had about a 30 percent lower risk of
cardiovascular disease over five years.
In a follow-up email to Reuters Health, Hruby and colleagues pointed
to the PREDIMED trial as an example of a prospective randomized
trial that supports their finding.
Dr. David Seres, director of medical nutrition at Columbia
University Medical Center in New York, said the controversy over
saturated fat “will continue to rage on until we’re able to do an
actual and effective randomized trial, which will take hundreds of
millions of dollars and decades to do.”
Seres, who was not involved with the new study, believes patients
are still going to advised by their doctors to limit saturated fats.
"It’s my opinion that that’s going to turn out to be correct, but
again I wish I had better data to be sure of my advice," he said.
SOURCE: http://bit.ly/1hbbBZx Journal of the American College of
Cardiology, online September 28, 2015.
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