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Heart studies add to fish-oil controversy.

Heart studies add to fish-oil controversy

As consumers rush to buy fish-oil capsules as a protection against coronary artery disease, scientists are mulling over equivocal results presented last week at the American Heart Association meeting in Washington, D.C.

In the past decade, studies have shown that fish-oil fatty acids seem to protect against atherosclerosis, a fatty buildup on artery walls. That evidence suggested a role for fish oil in treating coronary angioplasty patients, who are at high risk of vessel reclosure. The angioplasty procedure opens clogged blood vessels but injures them in the process. Up to 40 percent of angioplasty patients experience arterial renarrowing, which can lead to a heart attack or stroke. Drugs such as aspirin have failed to prevent vessel closure after angioplasty, but researchers had high hopes for fish oil. However, scientists studying the treatment offer mixed reviews.

Weighing in with positive evidence, Mark R. Milner of the Washington (D.C.) Hospital Center and his colleagues report that large fish-oil doses can "dramatically improve" the results of angioplasty. Milner and other scientists suggest the omega-3 fatty acids in fish oil protect angioplasty patients by minimizing vessel inflammation and scarring. Angioplasty often tears the vessel wall, possibly leading to a buildup of platelets, blood fats and scar tissue that later close the artery.

Milner's team looked at 194 angioplasty patients who were randomly assigned to treatment or control groups. Those in the fish-oil group took nine capsules containing 4.5 grams of omega-3 fatty acids per day for six months -- the daily equivalent of that found in about two cans of sardines. Controls received conventional care but no fish oil. Both groups were advised to eat a low-fat, low-cholesterol diet.

After six months, Milner and his colleagues evaluated their patients. "Our results showed a significant reduction in the clinical restenosis [closure] rate," Milner says. "The control group had a 35.4 percent reocclusion rate and the fish-oil group had only a 19 percent reocclusion rate."

That finding echoes an earlier study published in the Sept. 22 NEW ENGLAND JOURNAL OF MEDICINE. Gregory J. Dehmer of the Dallas Veterans Administration Medical Center and his colleagues found that 82 male patients treated with 5.4 grams of fish oil daily had a 16 percent rate of vessel renarrowing, compared with a control-group rate of 36 percent (SN: 9/24/88, p. 197).

Fish oil gets a very different report card from Gregg J. Reis and colleagues at the Beth Israel Hospital in Boston. These researchers studied 186 randomly assigned angioplasty patients. Those in the treatment group got 6 grams of omega-3 fatty acids per day, while control patients received olive-oil placebo capsules. The researchers found that fish-oil patients had a 35 percent reocclusion rate, compared with 24 percent for controls. "We concluded that fish oil offered no protective effect in restenosis," Reis says.

Reis suggests Milner and Dehmer's results may be tainted by a defect in study design. In both of those studies, he notes, patients knew they were being given fish oil and researchers evaluating the vessel occlusion may have been unintentionally biased, tending to observe less vessel closure in fish-oil patients. In contrast, researchers and patients in the Beth Israel effort were unaware of who received the fish oil and who took the olive oil.

On the other hand, Reis' group may have introduced problems of its own by using olive oil as a placebo. Milner points out that olive oil is an unsaturated fat that may help prevent plaque buildup on artery walls.

Most researchers agree on the need for further study and a cautious approach to fish-oil treatment. Fish oil has drawbacks ranging from its "fishy taste" to possible bleeding complications. As for the current consumer craze, most experts say people are better off simply eating more fish dinners.
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Author:Fackelmann, Kathy A.
Publication:Science News
Date:Nov 26, 1988
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