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The Minnesota Coronary Survey was particularly
interesting. It included both men and women,
and both groups ate diets in which fat provided
about 40% of the calories. The diet of one group,
however, was high in cholesterol and heavy in
unsaturated fats: just 9% of the calories came from
saturated fat. The diet of the other group contained
much less cholesterol and twice the proportion of
unsaturated fat. When the study ended, researchers
found no difference among the cardiovascular
events, deaths from heart disease, or mortality
from any cause experienced by the two groups.
Because the intervention studies on saturated
fat consumption and heart health have shown no
clear association, a group of epidemiologists at
Harvard School of Public Health and Children’s
Hospital in Oakland, California, performed a
meta-analysis to summarize the overall findings
to date of all the prospective studies published by
2009. Their analysis, published in early 2010,
included data on almost 350,000 subjects
gathered during more than 20 years of observation.
The authors determined that “there is no
significant evidence for concluding that dietary
saturated fat is associated with an increased risk
of coronary heart disease or cardiovascular
disease.” In another 2009 study that looked at
dairy foods (including milk, cheese, and butter),
the authors found that “there is no clear evidence
that dairy food consumption is consistently
associated with higher risk” of cardiovascular
disease. In yet another meta-analysis, published
in 2010, investigators looked at the relation
between red meat and heart disease, diabetes,
and stroke. They found no increased risk. Interestingly,
they did find increased risk associated
with processed-meat consumption.
Not Better than Butter
If any kind of fat truly is very dangerous to eat, it
may be trans fat, the manufactured variety that
includes margarine and hydrogenated shortenings
and cooking oils. In the Nurses’ Health Study,
those women in the highest range of margarine
consumption had a 35% higher risk of heart
disease. And the Framingham study of men found
a strong risk of heart disease associated with
margarine but not with butter.
This is quite ironic because for many years,
margarine was recommended as a healthier
alternative to butter! The prejudice against butter’s
saturated animal fat was strong. Although there
was no proof that margarine’s polyunsaturated fats
were more healthful, they seemed like a perfect
substitute. Now that the studies are in, we know
that the trans fat modification applied to the
polyunsaturated fats made them deadly, whereas
butter is probably harmless despite being rich in
saturated fats and cholesterol.
The confusion over margarine illustrates how
leaping to conclusions based on preliminary data is
not just bad scienceit can actually mislead people
into an early grave. Many diet advocates, when
pressed, will admit that full proof is not yet in for
their favorite theory, but they argue that the answer
is too important to wait for the years of testing.
“What if people die in the meantime?” they ask.
“Let’s go ahead with what we think is healthier for
now,” they reason. The case of trans fat and margarine
shows that “doing good” is not so simple.
Promotion of margarine likely did shorten lives;
the fears of butter were overblown, and trans fat is
more dangerous than first appreciated. Burkitt’s
fiber theory caused people to waste a lot of money
on fiber-enhanced processed foods, but thankfully,
it hurt only their pocketbooks. Pushing margarine
over butter had far more lethal effects.
Are Some Fats Good for You?
Browse the oils or chips aisles at the supermarket,
and you’re bound to see products touting the
supposedly healthful properties of omega-3 fats or
olive oil. Researchers grew interested in these
particular forms of fat when they learned rates of
heart disease seem to be lower in regions where
people eat a lot of these oils.
Omega-3 fats, for example, are found in coldwater
fish, as well as in animals, like seals, that eat
cold-water fish. People native to the Arctic and
other regions with few vegetables largely eat fat
TIMELI NE
Fat and Heart Disease: Advice and Evidence
SCIENCE POLICY
1961 The American Heart
Association issues an alert
that dietary fat is a dangerous
substance
1977 The U.S. government
issues diet advice for the first
time, recommending that fat
consumption be reduced to
30% of total calories
1950s Ancel Keys, M.D., publishes early
results of the Seven Countries study,
a post-WWII, cross-cultural evaluation of
the link between consuming a rich diet and
developing heart disease
1977 The Framingham Heart
Study finds no link between total
1981 The Framingham, Puerto Rico,
and Honolulu heart studies all find that
subjects having heart disease ate no
more or less fat than healthy peers did
1989 The Minnesota Coronary
Survey serves diets greatly reduced in
cholesterol and saturated fat to hospital
patients for one to two years but finds
no change in risk of cardiovascular
illness or death compared to subjects
fed more cholesterol and twice as
much saturated fat
cholesterol levels in the blood and
risk of heart disease
1982 The MRFIT study shows that men who eat
less fat have at best a slightly reduced risk of heart
disease after six to eight years
1997 The Nurses’ Health Study
finds no strong association tying
total fat or saturated fat consumption
to heart disease
2005 The U.S. updates dietary guidelines to
state that “high intake of saturated fats, trans fats,
and cholesterol increases the risk of unhealthy
blood lipid levels, which, in turn, may increase the
risk of coronary heart disease”
2006 The Women’s Health
Initiative trial finds no reduction
of the incidence of heart disease
among women who reduced the
fat and increased the fruits and
vegetables in their diet
2009 The American Heart Association
advises limiting total fat to 24%–35% of
total energy consumed, trans fat to less
than 1%, and saturated fat to 7%
2010 A meta-analysis of all prospective cohort
studies published before September 2009 finds no
significant evidence linking saturated fat consumption
to cardiovascular disease. Another metaanalysis
finds no clear evidence that dairy food
consumption is consistently associated with
cardiovascular disease. A third meta-analysis shows
no evidence of increased risk with red meat
consumption (but does find increased risk with
processed meat consumption)
230 VOLUME 1 · HISTORY AND FUNDAMENTALS
FOOD AND HEALTH 231