Is Fish Oil Good for What Ails You?

Grapefruit & breast cancer, p. 9 Spices...or medicine? p.10 How to pick the best pasta sauce, p. 13 OCTOBER 2007 VOLUME 34 / NUMBER 8 CENTER FOR SCIENCE IN THE PUBLIC INTEREST $2.50 Is fi sh oil good for what ails you? BY BONNIE LIEBMAN t fi rst, the omega-3 fats in fi sh oil were only sup- “In the nutrition world, it’s one of the biggest success posed to prevent sudden death heart attacks. stories in decades,” says heart expert William Harris of the University of South Dakota. “The downsides are so But in the last few years, experts have looked at minimal that the burden of proof for a benefi t doesn’t omega-3s and asthma, cancer, the aging brain, demen- have to be that high.” tia, neurological diseases, diabetes, infl ammatory bowel disease, rheumatoid arthritis, kidney disease, lupus, But that doesn’t justify the unfounded promises on osteoporosis, eye health, mental health, and more. some food and supplement labels, says Harris. “We don’t want people hawking fi sh oil and raking in a lot of So far, the evidence is too skimpy to say that omega-3s money based on sloppy data.” matter for most health problems other than heart disease. But the sheer number of potential benefi ts makes Here’s the latest on what omega-3s can—and can’t— you wonder if you’re getting enough. do. Photos:fotolia.com/© zampa (background), LimJerry(fish),© Paul© Maguire (stethoscope). Photo Illustration:Jorge Bach. C o n t i n u e d on page 3. COVER STORY Is fi sh oil good for what ails you? reyers Smart! Yogurt claims to “boost your brain” and “helps support a healthy heart.” Silk Plus Omega-3 DHA Soy Milk “helps support heart, brain & eye health” (see “Omega-3 Madness,” p. 7). USA Today called omega-3 fats “one of 2007’s hottest food additives.” Of course, you can also get them in pills or good old-fashioned fi sh. Are omega-3s miracle fats or a money-making fad? Here’s the evidence so far. Heart Disease artery that brings oxygen to heart muscle Harris. “Researchers have recognized that gets blocked.) people with an ongoing fi brillation prob- In Australia and Britain, government Sudden death usually occurs when the lem are not a good model to answer the experts now advise healthy people to ventricles—the major pumping cham- question of whether omega-3s are good eat enough fi sh to get 400 to 600 mil- bers of the heart—lose their normal for general heart health.” ligrams a day of the long-chain omega-3 rhythm. Instead of one strong, synchro- Most people who have a sudden death fats—DHA (docosahexaenoic acid) plus nized heartbeat that pushes blood out heart attack, he explains, “have a normal EPA (eicosapentaenoic acid). of the heart, the heart muscle goes into heart rhythm until a lack of oxygen Although the U.S. government has no ventricular fi brillation, a series of rapid, throws them into ventricular fi brillation.” similar recommendation, the American irregular, and unsynchronized contrac- In contrast, “people who need a defi - Heart Association advises people who tions that are too weak to send blood brillator have structural heart disease or have heart disease to take a daily supple- throughout the body. Without a defi bril- a heart that’s so damaged by a previous ment with 1,000 mg (1 gram) of DHA plus lator to shock the heart back into rhythm, heart attack that they can easily fl ip into EPA. And it recommends that healthy the person dies. fi brillation. Their problem is not driven people eat fi sh (preferably fatty fi sh like So scientists decided to test fi sh oil by lack of oxygen and blood fl ow but by salmon) at least twice a week. in people who had had a defi brillator electrical problems.” “I can’t think of a nutrient that’s more implanted in their chest because they Overall, he says, “these results don’t important for heart disease prevention than had episodes of ventricular fi brillation or hurt the advance of omega-3s. They’re omega-3s,” says William Harris of the Uni- ventricular tachycardia kind of a hiccup.” versity of South Dakota’s Sanford School of (fast heartbeat). What about trials that Medicine. (Harris is a consultant to several But in one randomly assign companies that sell omega-3 pills.) European and people without In most studies, people who report one U.S. tri- defi brillators to eating more fi sh are less likely to die of a al—involving take—or not heart attack than those who eat less fi sh. a total of 600 take—fi sh One meta-analysis pooled 13 studies that people—patients oil? tracked more than 220,000 people for an who took fi sh oil The largest, average of 12 years.1 Compared to people (800 or 1,200 mg of an Italian study who ate no fi sh, “those who ate fi sh at DHA plus EPA a day) called GISSI, ran- least fi ve times a week had a 40 percent had no fewer episodes of Experts recommend two servings a week domly assigned lower risk of death from heart disease,” ventricular fi brillation or of fatty fish like salmon. more than 11,000 notes Harris. tachycardia than those people who had At fi rst, researchers found that fi sh eat- who took a placebo.2,3 And in the U.S. recently suffered a heart attack to take ers had a lower risk of sudden death heart study, those fi sh oil takers who got their either fi sh oil (850 mg of DHA plus EPA a attacks, which account for half of all defi brillators because of tachycardia had day) or to see their doctor as usual. After deaths from cardiovascular disease. (Most more arrhythmias.3 3½ years, the fi sh oil takers were half other deaths are due to myocardial infarc- Did those studies quash the theory that as likely to have died of a sudden death tions—heart attacks that occur when an fi sh oil prevents arrhythmia? No, says heart attack.4 Photos: © Elvin/fotolia.com ©Photos: (right), see cover (top). > > > > > NUTRITION ACTION HEALTHLETTER ■ OCTOBER 2007 3 COVER STORY But the study wasn’t from 35,000 to 88,000 people for 6 to 14 “It’s not that omega-6 fats are bad,” top-notch. It didn’t years, those who ate more fi sh or omega-3 says Chen. “We can’t survive without compare fi sh oil to a fats had no lower risk.7 them. It’s a question of balance.” placebo so it wasn’t double-blind “It’s not surprising that these epide- Before industrialization, some 200 —that is, both researchers and patients miological studies are inconsistent,” says years ago, he says, we used to eat equal knew who was taking fi sh oil. Yong Q. Chen of the Wake Forest Univer- amounts of omega-6 and omega-3 fats. Several new studies are under way. “A sity School of Medicine in Winston- Now we eat far more omega-6s than bigger, double-blind, placebo-controlled Salem, North Carolina. “Most studies omega-3s. Why? “Vegetable oils became study is being done in Europe,” says Har- don’t have ways to verify how much readily available and most are concen- ris. “And GISSI is doing a trial to prevent omega-3 fats people actually eat.” trated in omega-6,” says Chen. heart failure in people who already have The evidence for prostate cancer is Nor is Chen enthusiastic about ALA, heart disease and a prevention trial in also mixed. For example, in a study that the omega-3 fat in fl ax, soy, and canola healthy people.” followed 47,000 U.S. health profession- oils. “DHA is highly concentrated in the How might omega-3s make a differ- als for 12 years, those who ate fi sh more sperm, eye, and brain,” explains Chen. ence? “We know that high doses of fi sh than three times a week had a 45 percent “The body can convert ALA to EPA or oil—about 3 or 4 grams a day—lower tri- lower risk of metastatic prostate cancer DHA, but it’s very ineffi cient.” glycerides,” says Harris. But the dose used than those who ate fi sh less than twice a He recommends eating more fatty fi sh in GISSI wasn’t high enough to do that. month.8 But some studies found no link or taking fi sh oil. “What’s the worst out- Another possibility: “We found that at all.7 come?” he asks. “That it’s good for your omega-3s slowed heart rate by about Still, researchers are chasing clues that heart?” fi ve beats per minute,” notes Harris. That might explain how omega-3s may infl u- could make irregular heartbeats (arrhyth- ence cancer risk. For example, a recent Eye Disease mias) less likely. study fed high or low levels of omega-3 You don’t have to look far to see why “If you polled most experts, they’d fats (including DHA and EPA) to mice scientists think the omega-3 fat DHA may probably say that omega-3s work by that are missing a gene—called Pten— be good for eyes. reducing the risk of arrhythmia,” says that suppresses tumors.9 “Structurally, the retina is made of Harris. “Pten is a frequent abnormality in DHA,” says Emily Chew, deputy director He’s not so optimistic about ALA human prostate cancer,” says Chen.

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