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 Guidelines from the U.S. federal government and
recommendations from the American Heart Association call for
increased consumption of polyunsaturated fatty acids and lower
consumption of saturated fats.
But researchers found people's risk of heart disease varied little
based on how much of those fats they ate.
Polyunsaturated fats generally come from plant-based foods such as
nuts, seeds and vegetable oils. Omega-3 fatty acids, a type of
polyunsaturated fats, are found in fish.
On the other hand, most saturated fats in the American diet come
from foods of animal origin, including red meat and high-fat dairy
products.
The authors of the new review say uncertainties in evidence have led
to considerable variation in international guidelines on fat intake.
They also say the use of self-reported diet information may have
resulted in problems classifying the different fatty acids that
people eat.
"We intended to help resolve the existing uncertainties around fatty
acids and their potential association with coronary heart disease
risk," Dr. Rajiv Chowdhury told Reuters Health in an email.
Chowdhury, from the University of Cambridge in the UK, led the
review that was published in the Annals of Internal Medicine.
He and his colleagues collected data from 72 previously published
studies of more than 600,000 people from 18 countries.
Those included studies that measured the types of fatty acids people
consumed or had in their blood, as well as those that randomly
assigned people to take fatty acid supplements or not.
All of the studies followed participants to see who developed heart
problems like heart attacks, heart disease or coronary
insufficiency.
When Chowdhury and his team analyzed data on fatty acid intake, they
found that none of the types of saturated or polyunsaturated fats
had a significant impact on heart disease risk. However, consumption
of trans fat — found in some processed foods and some forms of stick
margarine — was tied to a 16 percent increase in risk. Guidelines
call for avoiding trans fats altogether.
When the researchers examined markers of fatty acids in the blood,
they also found little difference in heart risk based on levels of
saturated or polyunsaturated fats. But the results varied for
individual fatty acids.
The researchers found that higher blood levels of two forms of
omega-3 fatty acids — docosahexaenoic acid (DHA) and
eicosapentaenoic acid (EPA) — were associated with a lower risk of
heart disease.
They did not see a significant reduction in heart disease risk with
any of the fatty acids in studies that randomly assigned some
participants to take them in supplement form. Doses used in the
studies ranged from 2 to 5.5 grams per day of added oils and 0.3 to
6 grams per day when capsules were used.
"The pattern of findings from this review did not support the
current cardiovascular guidelines that encourage high consumption of
total long-chain omega-3 polyunsaturated fatty acids and suggest
reduced consumption of total saturated fatty acids," Chowdhury said.
But he said further careful research and specifically large-scale
clinical trials are required before making a conclusive judgment and
changing dietary guidelines.
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Linda Van Horn, from the Northwestern University Feinberg School
of Medicine in Chicago, told Reuters Health the study was well done
and demonstrated that some fatty acids are better than others. But
it's not enough to change current guidelines, she added.
Van Horn chaired the 2010 U.S. Dietary Guidelines Advisory Committee
which was involved in creating federal recommendations and is a
spokesperson for the American Heart Association. She was not
involved in the new review.
"People need to eat as has been recommended — this paper changes
nothing about the adverse impact of saturated fat," she said.
Van Horn pointed out that there is no biological need for saturated
fats.
"People like their burgers and their hot dogs," she said, "but
this study still doesn't make them nutritious."
"Frankly I'm really worried this will confuse consumers," Duffy
MacKay told Reuters Health of the findings.
MacKay is senior vice president of scientific and regulatory affairs
for the Council for Responsible Nutrition, a trade association in
Washington, D.C. He was not involved in the new research.
"It may possibly be used by some as a license to ignore these
decades of good advice, common sense and Grandma's advice, and go
right for the cheese breads," he said.
He said the report doesn't change what's perceived as a
heart-healthy diet.
"I think the concept of a diet high in polyunsaturated fat, low
in saturated fat and low in trans fat still holds a lot of weight
based on decades of research," he said.
MacKay also said this report does nothing to change the need to get
certain fatty acids in the diet.
"It all pointed toward the contribution of EPA and DHA as
maintaining heart health and preventing cardiovascular disease,
which to me is promising," he said.
Van Horn said the emphasis is still on choosing plant-based foods
and fish.
"It's just that now we'll have the ability to be more specific about
what the better unsaturated fats choices are," she said.
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Source: http://bit.ly/1i46lF7
Annals of Internal Medicine, online March 17, 2014.
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