Modernist-Cuisine-Vol.-1-Small

4
Trials of Omega-3 Fats and Heart Disease
The three largest randomized, controlled clinical studies of omega-3 fats to date all studied people
who already had suffered heart attacks, which limits the applicability of their results to the general
population. A pooled analysis of 48 randomized clinical trials, however, found no reduction in
mortality or major cardiovascular problems among people who increased their intake of omega-3.
Trials of Dietary Fat and Cancer
Cancer is as much a public health priority as heart disease, so researchers have also investigated with
some rigor whether eating fat is connected to cancer risks. So far, however, science has established no
such link. The randomized, controlled clinical trials summarized below found that lowering fat
consumption does not decrease the incidence of cancer.
Study 1: DART 1
Studied outcome: death from any cause
among men who had already suffered a heart
attack
Study duration: two years
Intervention group: advised to eat oily fish or
given omega-3 supplements
Participants: 1,015
Deaths: 93 (9.16%)
Control group: regular diet
Participants: 1,018
Deaths: 131 (12.86%)
Comparative risk: lower
Study 2: DART 2
Studied outcome: death from any cause
among men who had already suffered a heart
attack
Study duration: three to nine years
Intervention group: advised to eat oily fish or
given omega-3 supplements
Participants: 1,571
Deaths: 283 (18.0%)
Control group: regular diet
Participants: 1,543
Deaths: 242 (15.7%)
Comparative risk: not significantly different
Study 3: GISSI-Prevenzione
Studied outcome: death, stroke, or heart
attack among subjects who had already
suffered a heart attack
Study duration: 3.5 years
Intervention group: daily omega-3
supplements, half with vitamin E and half
without
Participants: 5,665
Deaths or events: 556 (9.8%)
Control group: no daily supplements or
vitamin E supplement alone
Participants: 5,658
Deaths: 621 (11.0%)
Study 1: Women’s Healthy Eating
and Living
Studied outcome: new or recurring breast
cancer
Study duration: seven years
Intervention group: repeated counseling and
classes to promote low-fat (15%–20%) diet
Participants: 1,537
Participants with disease: 256 (16.7%)
Control group: cursory, one-time advice
Participants: 1,551
Participants with disease: 262 (16.9%)
Comparative risk: not significantly different
Study 2: Women’s Health Initiative
Studied outcome: new breast cancer
Study duration: eight years
Intervention group: low-fat (24% fat) diet
Participants: 19,541
Participants with disease: 655
(0.42% per year)
Control group: regular (35% fat) diet
Participants: 29,294
Participants with disease: 1,072
(0.45% per year)
Comparative risk: not significantly different
Study 3: Women’s Health Initiative
Studied outcome: ovarian cancer
Study duration: eight years
Intervention group: low-fat (24% fat) diet
Participants: 19,541
Participants with disease: 0.036% per year
Control group: regular (35% fat) diet
Participants: 29,294
Participants with disease: 0.043% per year
Comparative risk: not significantly different
Study 4: Polyp Prevention Trial
Studied outcome: prostate cancer
Study duration: four years
Intervention group: low-fat (24%), high-fiber
(34 g/d) diet
Participants: 627
Participants with disease: 22 (3.5%)
Control group: regular diet (34% fat, 19 g/d)
Participants: 603
Participants with disease: 19 (3.2%)
Comparative risk: not significantly different
Comparative risk: lower
−50% −29% 0
+50%
−50% 0 +15% +50%
−50% −20% 0
+50%
−50% −4%
+50%
−50% −9% 0
+50%
−50% −17% 0
+50%
−50% 0 +12% +50%
Lower risk for
intervention group
Equal
risk
Higher risk for
intervention group
Lower risk for
intervention group
Equal
risk
Higher risk for
intervention group
(−61%)
(+210%)
and fatty meat from fish or marine mammals yet
seem to have lower rates of heart disease than
people who eat a “Western” diet.
But, as we have seen with fiber, the “French
paradox,” and other cases, ecological studies alone
can be very misleading. Several randomized
clinical trials have examined whether adding
omega-3 fats to the diet has any substantial effect
on heart disease risks. So far, the answer seems to
be that any benefits are small at best. One short
trial, the Diet and Reinfarction Trial (DART 1),
reported a significant reduction in mortality rates
among heart attack victims advised to start eating
more fatty fish. But when the study was repeated
with more subjects for a longer period, the benefit
did not appear again. So far, no trials have lasted
long enough to provide a truly reliable answer that
can be applied to the healthy population (see
charts above).
Olive oil has been hailed in some quarters as
a “miracle” fat that explains a lower incidence of
heart disease among people in Spain, Italy,
Greece, and other regions where a so-called
Mediterranean diet is common. Ancel Keys
speculated that the Mediterranean diet was low in
total fat and was healthful for that reason. The
latest theory, ironically enough, is that high
consumption of olive oiland of extra-virgin
olive oil in particularis responsible.
Unfortunately, as of this writing, no randomized,
controlled studies have been reported that
test whether eating olive oil separatelyrather
than as part of the Mediterranean diet as a
wholecan lower the risk of disease. The best
data available instead come from meta-analyses of
observational studies and case–control studies in
people who already had heart disease or were at
high risk. These “studies of studies” suggest that
a Mediterranean diet might reduce risks of heart
disease and other chronic ailments. But the
meta-analyses cannot attribute those effects to
olive oil in particular.
One small study of 200 males who consumed
olive oil with varying amounts of phenolic acids
a group of chemicals with antioxidant and antiinflammatory
effectssuggested that the higher
the phenolic content, the more HDL cholesterol
increased and the more markers of oxidative stress
fell. What does this small study tell us about the
benefits of olive oil? Not much more than this:
perhaps, among the more than 230 chemical
compounds in olive oil, polyphenols are beneficial
THE CHEMIST RY O F
What’s in a Fat
First we were told that all fat was bad, then that all saturated
fat was bad. Now a closer look at the individual fatty
acids of which all fats are composed reveals that “good”
and “bad” fats really have similar chemical compositions.
Olive oil, which has a reputation as a healthful fat, is
mostly oleic acid, which does not raise LDL cholesterol. But
Not So Different
The graphs below show the total fat (left) and palmitic, oleic, and stearic fatty acids (in
purple, blue, and orange, respectively, at right) in 100 grams of olive oil, cooked bacon,
and cooked steak.
Total fat (g)
100
80
60
40
20
0
Olive oil
Bacon
Porterhouse steak
the fat in cooked steak is also nearly half oleic acid. And the
majority of bacon’s fat is oleic acid, too.
The principal other fats in cooked bacon and steak are the
saturated fats palmitic acid, which has been found to raise
LDL cholesterol (yet is also present in olive oil), and stearic
acid, which the body rapidly metabolizes into oleic acid.
Relative proportions (%)
100
Stearic acid
80
60
Oleic acid
40
20
Palmitic acid
0
Olive oil
Bacon
Porterhouse steak
232 VOLUME 1 · HISTORY AND FUNDAMENTALS
FOOD AND HEALTH 233