The analysis of 72 previous studies showed insufficient support for nutritional recommendations that advocate high consumption of polyunsaturated fats like omega-3 and omega-6, which is found in corn and sunflower oils, as well as some nuts and seeds.
Thee findings, published in the Annals of Internal Medicine, are the latest to show that supplements and vitamins may not work as well as purported to help patients prevent diseases. While past studies showed fish oil can lower unhealthy blood fats, blood pressure and reduce the risk of a second heart attack, research in recent years contradicted those findings, suggesting it has limited heart benefits.
“The current guidelines should reflect the most recent evidence that show that their apparent benefit for reducing coronary risk is potentially low,” Rajiv Chowdhury, the lead study author and a cardiovascular epidemiologist in the Department of Public Health and Primary Care at the University of Cambridge in the U.K., said in an e-mail.
A study presented at the heart association’s 2012 meeting found that taking fish oil, a form of omega-3 fatty acid, after cardiac surgery did not prevent a form of irregular heartbeat that can cause blood clots and strokes. That year also saw a review of 20 trials over 24 years published in the Journal of the American Medical Association find that fish oil supplements failed to lower the risk for a range of illnesses, including heart attacks, strokes or death. A study in 2010 published in JAMA found fish oil did not prevent recurrences of atrial fibrillation.
Separate research published in JAMA Internal Medicine found that daily omega-3 supplements was not associated with a lower risk for heart attack, stroke or cardiovascular death in older patients with age-related macular degeneration, an eye disease.
Current heart association guidelines recommend people consume about two servings of fatty fish each week. They also recommend that 5-10% of total daily calories come from omega-6 sources. The guidelines suggest replacing saturated fats, found in meat, full-fat dairy products and coconut and palm oils with polyunsaturated fats.
In addition to salmon, omega-3 fatty acids are found in halibut, sardines, trout and tuna. They also added to other foods and packaged products such as eggs, cereal, pasta and margarine.
Researchers in the most-recent report analyzed 72 studies that looked at more than 600,000 patients from 18 countries. Of those, 40 involved initially healthy people; 10 recruited people with elevated cardiovascular risk factors; and 22 recruited people with cardiovascular disease.
In 17 studies of more than 75,000 patients, they found no evidence that supplementation with omega-3 fatty acids can reduce heart disease risk. More studies though are needed to see if omega-3 fats work to prevent heart disease in people who are initially healthy.
The analysis supported current guidelines restricting consumption of foods high in trans fats. The study did not, however, find evidence that saturated fats pose a heart risk.