Page 30 - Fall2010

themselves into the fatty “foam cells” that populate below. These studies suggested that about one gram of long-chain omega-3
atherosclerotic plaques, are oxidized derivatives of fatty acids per day may prevent arrhythmia in patients prone to chronic heart
linoleic acid. failure or in patients recovering from a recent heart attack. They also sug-
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The obvious implication of these studies is gested that long-term use of fish oils for more than four years may actually
that the oxidative destruction of PUFAs in the LDL increase mortality from heart disease and all causes.
membrane, but not the concentration of cholesterol Many other groups eating traditional diets appear to be free or nearly
carried in the blood by these LDL particles, deter- free of heart disease, and a high intake of marine oils is not a universal trait
mines the development of atherosclerosis. It is no of these diets. The main source of fat for the Masai, for example, is highly
wonder, then, that trials attempting to prevent heart saturated butterfat. The inhabitants of Tokelau consume a diet based mostly on
disease with diets rich in polyunsaturated vegetable coconut and to a lesser extent on seafood, and even the seafood they prepare
oils failed so miserably. contains only two percent of its calories as long-chain omega-3 fatty acids. 76
The inhabitants of Kitava consume about two percent of their total calories
DO FISH OILS PREVENT HEART DISEASE? as omega-3 fatty acids, which is greater than the amount that Tokelauans
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Researchers in the 1970s suggested that the consume but much lower than the amount that the Inuit consume. The tradi-
high content of omega-3 fatty acids in the diet of tional diet of Crete provides most of its fat as saturated butterfat from cheese
the Greenland Inuit may have protected them from and as monounsaturated olive oil, and contains very little fish. If we are to
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heart disease by lowering their cholesterol and offer a hypothesis about what protects all these groups from heart disease,
triglyceride levels. Since then, dozens of random- we must first identify what their traditional diets share in common. The most
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ized, controlled trials have tested the effect of fish obvious place to start is the complete absence of refined foods. A very high
oil supplementation on total and cardiovascular intake of marine oils, by contrast, is a specific peculiarity of the Inuit diet.
mortality, discussed in more detail in the sidebar

FISH OILS AND HEART DISEASE: A CLOSER LOOK

Dozens of randomized, controlled trials have tested the effect of fish oil supplementation and increases in the intake
of fatty fish on total and cardiovascular mortality. Virtually all of them have been conducted in people with established
heart disease taking drugs such as statins and aspirin, and most of them have lasted fewer than two years. In 2004, the
Cochrane Collaboration published a massive review and meta-analysis of these trials. Meta-analyses pool the data of
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many studies together in an attempt to show the big picture and test whether methodological differences between trials
or random chance are more likely to account for differences in results. When the authors pooled the data from forty-eight
trials lasting longer than six months, the only effect that could be distinguished from chance was a reduced risk of heart
failure. Fish oil provided no reduction in total or cardiovascular mortality.
Trials lasting less than one year were most likely to show positive results, while the only trial lasting more than four
years—the Diet and Reinfarction 2 (DART 2) trial—showed a 15 percent increase in total mortality and a 30 percent
increase in cardiovascular mortality. DART 2 used dietary advice to increase fatty fish intake in addition to fish oil supple-
mentation, so could not be placebo-controlled or double-blind, and unfortunately funding problems led to interruptions
of the recruitment process in the middle of the trial. Nevertheless, with over three thousand participants it was one of the
largest fish oil trials ever conducted and, with over four years follow-up, it was the longest fish oil trial ever conducted.
Thus, we should not casually dismiss the findings of this trial.
A recent meta-analysis brought to light eleven trials that were placebo-controlled and lasted more than one year.
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Pooling the data from these studies together showed that fish oil reduced the relative risk of cardiovascular death by 13
percent and reduced the relative risk of all-cause mortality by 8 percent.
The Italian GISSI-Prevenzione and GISSI-Heart Failure trials were the largest included in this meta-analysis and were
responsible for most of the effect. These trials, together with the DART 1 trial, suggested that fish oil may prevent arrhyth-
mia in patients with chronic heart failure and patients who have recently survived a heart attack. Researchers provided
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participants with roughly one gram of long-chain omega-3 fatty acids per day. The GISSI trials found a long-term benefit
over the course of almost four years in heart failure patients but a much shorter-term benefit concentrated in the first year
of the study in patients who had recently undergone a heart attack. The DART 1 trial similarly found an early benefit of
fatty fish consumption and fish oil supplementation in patients who had recently suffered from a heart attack. Fish oil thus
seems likely to prevent very specific types of heart failure rather than to prevent heart disease more generally.
None of these trials provided any evidence that healthy people benefit from taking fish oil or that doses higher than
one gram of omega-3 fatty acids per day provide any benefit over smaller doses. The results of the DART 2 trial are par-
ticularly concerning because, like the results of the Wadsworth Veterans Administration Hospital Study (see sidebar on
page 29), they suggest that high intakes of PUFAs may increase the risk of morbidity and mortality when consumed over
the course of many years.

30 Wise Traditions FALL 2010