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| Kalaöljy kapseleita Fish oil capsules (Photo credit: Wikipedia) |
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By ANAHAD O’ CONNOR
While sales of fish oil have been doubling worldwide, trials have shown it has no effect on health.
Fish oil is now the third most widely used dietary supplement in the United States, after vitamins and minerals, according to a recent report from the National Institutes of Health. Consumers believe the omega-3 fatty acids in the supplements will protect their cardiovascular health.
But the vast majority of clinical trials have found no evidence that fish lowers heart attack and stroke rates. From 2005 to 2012, at least two dozen studies of fish oil were published, most of which looked at whether fish oil could prevent heart disease in high-risk groups. All but two of the studies found that compared with a placebo, fish oil showed no benefit.
Most fish oil supplements are rich in two omega-3 fatty acids that can have a blood-thinning effect, much like aspirin, that may reduce the likelihood of clots. Omega-3s can also reduce inflammation, which plays a role in atherosclerosis. And the United States Food and Drug administration has approved at least three prescription types of fish oil – Vascepa, Lovaza and a generic form – for the treatment of very high triglycerides, a risk factor for heart disease.
Some of the earliest enthusiasm for fish oil goes back to research carried out in the 1970s by the Danish scientists Dr. Hans Olaf Bang and Dr. Jorn Dyerberg. They determined that Inuits living in northern Greenland had remarkably low rates of cardiovascular disease, which they attributed to an omega-3 rich diet consisting mainly of fish, seal and whale blubber. Dr. George Fodor, a cardiologist at the University of Ottawa, outlined flaws in much of this early research, and he concluded that the rate of heart disease among the Inuit was vastly underestimated. But the halo effect around fish oils persists. Several studies from the 1990s, including an Italian study that found that heart attack survivors who were treated with a gram of fish oil daily had a drop in mortality, bolstered the case for fish oil.
Dr. James Stein, the director of preventive cardiology at University of Wisconsin Hospital and Clinics, said the early fish oil studies took place in an era when cardiovascular disease was treated very differently than it is today, with far less use of statins, beta blockers, blood thinners and other intensive therapies. So the effect of fish oil, even if it had been minor, he said, would have been more noticeable.
Dr. Stein also cautions that fish oil can be hazardous when combined with aspirin or other blood thinners.
But some experts say the case for fish oil remains open. Dr. JoAnn Manson, the chief of preventive medicine at Brigham and Women’s Hospital in Boston, said the clinical trials had focused on people who already had heart disease or were at very high risk. Fish oil has also been promoted for the prevention of a variety of other conditions, including cancer and Alzheimer’s and depression.
“But I do think people should realize that the jury is still out,” she said, “and that they may be spending a lot of money on these supplements without getting any benefit.”
Taken from TODAY Saturday Edition, The New York Times International Weekly, April 11, 2015
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