"We are seeing the potential for negative effects at really high levels of omega-3 fatty acid consumption. Because we lack valid biomarkers for exposure and knowledge of who might be at risk if consuming excessive amounts, it isn't possible to determine an upper limit at this time," Norman Hord, associate professor in OSU's College of Public Health and Human Sciences and a coauthor on the paper, said.
Omega-3 fatty acids have anti-inflammatory properties, which is one of the reasons they can be beneficial to heart health and inflammatory issues. However, the researchers said excess amounts of omega-3 fatty acids can alter immune function sometimes in ways that may lead to a dysfunctional immune response to a viral or bacterial infection.
"The dysfunctional immune response to excessive omega-3 fatty acid consumption can affect the body's ability to fight microbial pathogens, like bacteria," the researcher said.
Generally, the researchers point out that the amounts of fish oil used in most studies are typically above what one could consume from foods or usual dosage of a dietary supplement.
However, an increasing amount of products, such as eggs, bread, butters, oils and orange juice, are being "fortified" with omega-3s. Hord said this fortified food, coupled with fish oil supplement use, increases the potential for consuming these high levels.
"Overall, we support the dietary recommendations from the American Heart Association to eat fish, particularly fatty fish like salmon, mackerel, lake trout or sardines, at least two times a week, and for those at risk of coronary artery disease to talk to their doctor about supplements," he said.
Hord said their main concern here is the hyper-supplemented individual, who may be taking high-dose omega-3 supplements and eating four to five omega-3-enriched foods per day.
The study is published in journal Prostaglandins.