OMEGA-3 CLAIMS fail to pass smell test
New analysis finds that taking fish-oil dietary supplements containing omega-3 fats does not reduce the risks of all-cause mortality, cardiac death, sudden death, heart attack or stroke, Joe Schwarcz writes.
It’s
a pretty common scenario. An observational study suggests that some food or beverage is associated with some aspect of health. A hypothesis is forged about the effect being due to some particular component. The component is isolated and tested in cell cultures and animals with some intriguing results. A few small-scale human studies follow and generate optimism.
Supplement manufacturers gear up and begin to flood the market with pills containing the supposed active ingredient. Their ads are supported by references to cherrypicked data, their hype couched with many a “may.” Personal testimonials of benefit pour in and profits mount. The results of randomized, controlled, double-blind trials (RCTs) begin to emerge with contradictory results. Marketers highlight the positive results and dismiss contradictory research as “flawed.” Sales continue to increase, with various producers claiming that their product is superior to that of competitors.
As controversy mounts, researchers undertake “meta analyses,” pooling data from the best available studies. Results suggest that the initial optimism cannot be supported but call for more studies. Sales begin to slump as manufacturers and their industry associations scramble to punch holes in the meta-analysis and issue news releases that reference the studies with positive findings. Regulatory agencies walk a fine line, having to take into account business interests, freedom of choice and public health. Consumers are left bewildered, not knowing whom to believe or trust.
In recent years, we have seen such scenarios unfold with vitamin E, calcium, beta-carotene, ginkgo biloba and, now, omega-3 fats.
The omega-3 saga can be traced back to the early 1970s, when Danish researchers discovered a surprisingly low incidence of heart disease in Inuit tribes despite a diet dominated by fatty fish. They wondered: Could this be due to the specific type of fat found in fish? After all, the molecular structure of these fats differed from the fats found in meat and most vegetables. Perhaps these polyunsaturated fats that feature a double bond on the third carbon from the end of the molecule, the so-called “omega carbon,” had some special cardioprotective property. This was a reasonable guess, given that other populations around the world consuming a fish-rich diet, such as the Japanese, also have a low incidence of heart disease.
Laboratory studies soon revealed that the omega-3 fats have antiinflammatory properties and reduce the clotting tendency of blood, both observations meshing with theories of reduced cardiac risk. There were also implications of reduced blood pressure and a slowing of the progression of arteriosclerosis. Then came evidence of a lowered incidence of abnormal heart rhythms in those who consume fish, and a decrease in trigly- cerides in their blood — both established risk factors for heart disease.
By the 1980s, supplement manufacturers were capitalizing on the tantalizing studies, filling capsules with various mixtures of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the two dominant fatty acids in fish oils. Recommended dosages were no more than educated guesses. The U.S. Food and Drug Administration essentially endorsed the supplements, allowing labels to state that “supportive but not conclusive research shows that consumption of EPA and DHA may reduce the risk of coronary heart disease.” Furthermore, the FDA approved a high-dose prescription mixture of EPA/DHA derived from fish oil for the treatment of high levels of triglycerides.
Before long, claims of protection against heart disease were joined by a plethora of others. Omega-3 fats were said to reduce the risk of cancers of the colon, breast and prostate, as well as that of macular degeneration and gum disease. They were also said to be useful in the treatment of depression and anxiety. There were claims of a slowing of cognitive decline in the elderly and improvement in attention-deficit hyperactivity disorder in children. Moms consuming fish oils supposedly gave birth to children with higher IQs. Even pets benefited from fish-oil supplements, sporting shinier coats. We were swimming in a sea of claims about the wonders of omega-3 fats, hooked on fish oil.
And then the double-blind studies started to appear and the scales began to fall from our eyes. Suddenly, we were confronted with headlines such as: Fish oil disappoints versus cancer, Fish oil won’t fix abnormal heart rhythms and Omega3s of No Added Benefit to Heart Attack Patients.
The highly respected j ournal Circulation featured a study demonstrating that among heart-attack survivors, 1,000 milligrams of purified omega-3 oils a day for one year was no better than olive oil at preventing sudden cardiac arrest, death, heart attack, stroke or the need for bypass surgery or angioplasty. The British Medical Journal published a study that found survivors of a heart attack or ischemic (clot-caused) stroke, or those with unstable angina (chest pain at rest), taking 600 milligrams of omega-3s a day for almost five years to be no better off than with a placebo when it came to reducing non-fatal heart attacks, strokes or deaths from cardiovascular disease.
Still, business was going along swimmingly for the fish oil-supplement industry until the publication of a recent meta-analysis in the Journal of the American Medical Association. It pooled the results of 20 high-quality randomized trials involving 68,000 people and found that supplementation with omega-3 fats did not reduce the risks of all-cause mortality, cardiac death, sudden death, heart attack or stroke. The researchers conclude that their findings “do not justify the use of omega-3 as a structured intervention in everyday clinical practice or guidelines supporting dietary omega-3 fat administration.”
The industry responded by claiming the analysis was flawed because many of the studies were on people already ill, and therefore might not apply to maintaining health. Furthermore, most studies, they said, didn’t control for the amount of fish people were already eating.
Given the size and number of the trials embodied in the metaanalysis, these seem to be weak counter-arguments. The analysis did, however, provide some comfort for people taking omega-3 supplements, in that no harmful effects were noted. It turns out, as it almost always does, that eating the whole food is better than some supplement shortcut.