CORVALLIS, ORE. — Effective modern drug therapies for heart disease may be one reason for conflicting findings on the benefits of omega-3 fatty acids, according to an analysis appearing in the December issue of theJournal of Lipid Research.

Fish oils and their omega-3 fatty acids may have positive effects on virtually all the same cardiovascular risk factors as such drugs as statins for high cholesterol, fibrates for high triglycerides, anti-thrombotics to thin blood, and other drugs with anti-inflammatory or anti-arrhythmia effects, said Donald Jump, author of the analysis from the Linus Pauling Institute at Oregon State University in Corvallis.

“Some of the early studies done on fish oil were prior to so many effective medications being widely available and heavily used,” said Dr. Jump, a principal at the Institute and a professor in O.S.U.’s College of Public Health and Human Sciences. “And people forget that nutrients, like fish oils, are less potent than prescription drugs and often have their best value when used for extended periods.

“When so many people in these studies are taking a regimen of medications to address the same issues that fish oil might also affect, it’s easy to understand why any added benefit from the fish oils is more difficult to detect.”

Studies in the 1970s involved Inuit Eskimos in Greenland who ate large amounts of fish and had low levels of cardiovascular disease. Since then, hundreds of studies have produced conflicting results.

“After decades of studying omega-3 fatty acids, it’s clear that they have value in primary prevention of heart disease,” Dr. Jump said. “It’s less clear how much impact fish oils have in preventing further cardiovascular events in people who already have heart disease. The studies done several decades ago showed value even for the patient population, but the more recent studies are less conclusive. We believe that one explanation is the effectiveness of current state-of-the-art treatments now being offered.”

The analysis also found it’s difficult to be certain of the amount of omega-3 fatty acids in farm-raised fish because they require dietary omega-3 fatty acid supplementation. Plant-derived sources of omega-3 fatty acids, such as those from flaxseed or chia seeds, have less benefit than omega-3 fatty acids from cold-water fish because of differences in how humans’ bodies process the nutrients.

Other research, according to the analysis, has shown omega-3 fatty acids may have benefits in improving visual acuity, improving cognitive function, reducing dementia and reducing inflammation. They may have benefits in relation to some types of cancer, such as colon cancer.

The U.S. Department of Agriculture and the National Institutes of Health supported the research. The Linus Pauling Institute studies micronutrients and their role in promoting health or preventing and treating disease.