Fish oil reduces heart attack and blood vessel disease

Fish oil can help reduce deaths from heart disease, according to new evidence reports announced today by the Agency for Healthcare Research and Quality. The systematic reviews of the available literature found evidence that long chain omega-3 fatty acids, the beneficial component ingested by eating fish or taking a fish oil supplement, reduce heart attack and other problems related to heart and blood vessel disease in persons who already have these conditions, as well as their overall risk of death. Although omega-3 fatty acids do not alter total cholesterol, HDL cholesterol, or LDL cholesterol, evidence suggests that they can reduce levels of triglycerides—a fat in the blood that may contribute to heart disease.

The review also found other evidence indicating that fish oil can help lower high blood pressure slightly, may reduce risk of coronary artery re-blockage after angioplasty, may increase exercise capability among patients with clogged arteries, and may possibly reduce the risk of irregular heart beats—particularly in individuals with a recent heart attack.

“These findings will help health care professionals and the public understand which benefits of omega-3 fatty acids have been scientifically proven and pinpoint areas where additional evidence is needed,” said Carolyn M. Clancy, M.D., AHRQ director. "Translating scientific evidence into information that can be used to improve health and heath care is key to AHRQ’s mission."

The evidence reports of the health effects of omega-3 fatty acids are part of a series conducted by AHRQ-supported Evidence-based Practice Centers at the request of the National Institutes of Health’s Office of Dietary Supplements, which plans to use the findings to develop research agendas on the issues. Five reports are currently being issued, and an additional six reports will be issued next year.

Paul M. Coates, Ph.D., director of NIH’s Office of Dietary Supplements, said, “The reports describe some positive findings as well as a number of areas where data are insufficient to draw conclusions about the efficacy and safety of omega-3 fatty acids. The Office of Dietary Supplements, in collaboration with other NIH institutes, will use these reports to develop appropriate research agendas for omega-3 fatty acids that will fill these gaps in knowledge.”

Findings from the three other AHRQ evidence reviews indicate that:

• Omega-3 fatty acids do not affect fasting blood sugar or glycosylated hemoglobin in people with type II diabetes, nor do they appear to affect plasma insulin levels or insulin resistance.

• Alpha-linolenic acid (ALA), a type of omega-3 fatty acid from plants such as flaxseed, soybeans, and walnuts, may help reduce deaths from heart disease, but to a much lesser extent than fish oil.

• Based on the evidence to date, it is not possible to conclude whether omega-3 fatty acids help improve respiratory outcomes in children and adults who have asthma.

• Omega-3 fatty acids appear to have mixed effects on people with inflammatory bowel disease, kidney disease and osteoporosis, and no discernible effect on rheumatoid arthritis.

The evidence reports and Evidence-based Practice Centers that produced them are: Effects of Omega-3 Fatty Acids on Cardiovascular Disease, Effects of Omega-3 Fatty Acids on Cardiovascular Risk Factors and Intermediate Markers for Cardiovascular Disease, and Effects of Omega-3 Fatty Acids on Arrhythmogenic Mechanisms in Animal and Isolated Organ/Culture Studies (Tufts-New England Medical Center EPC, Boston); Health Effects of Omega-3 Fatty Acids on Asthma (University of Ottawa EPC, Ottawa, Ontario); Health Effects of Omega-3 Fatty Acids on Lipids and Glycemic Control in Type II Diabetes and the Metabolic Syndrome, and on Inflammatory Bowel Disease, Rheumatoid Arthritis, Renal Disease, Systemic Lupus Erythematosus, and Osteoporosis (Southern California-RAND EPC, Santa Monica).

Summaries of evidence reviews are available on AHRQ’s Web site at http://www.ahrq.gov/clinic/epcindex.htm#dietsup, and on the National Guideline Clearinghouse Web site at http://www.guideline.gov (select “EPC reports”). Free printed copies are available from the AHRQ Publications Clearinghouse by calling 1-800-358-9295 or sending an e-mail to [email protected].