BETHESDA, Md., Aug. 25 (UPI) -- A five-year study by the National Institutes of Health found omega-3 supplements had no effect on cognitive decline, contrary to long-held beliefs by the medical community.
The study is the second in a month to question the efficacy of omega-3 supplements as part of health treatments. The supplements are a concentrated version of fish oils -- which can be found naturally in fish and marine algae -- that differs slightly from the naturally occurring version.
"Contrary to popular belief, we didn't see any benefit of omega-3 supplements for stopping cognitive decline," Dr. Emily Chew, deputy director of the Division of Epidemiology and Clinical Applications and deputy clinical director at the National Eye Institute, part of the NIH, said in a press release.
Researchers followed about 4,000 patients from 2006 to 2012 as part of the Age-Related Eye Disease Study 2. The average age of people in the study was 72, and 58 percent of them were female.
In addition to eye exams as part of the primary function of the study, participants were given cognitive tests every two years during the study. The eight-part tests were designed to measure immediate and delayed recall, attention and memory, and processing speed
The participants were split into four groups: one received omega-3; one received lutein and zeaxanthin, both of which are found in green vegetables; one was given omega-3, as well as lutein and zeaxanthin; and the other received a placebo.
Over the course of the study, published in the Journal of the American Medical Association, the participants all experienced some level of cognitive decline. The declines, researchers said, showed that none of the supplements made a difference.
"It may be, for example, that the timing of nutrients, or consuming them in a certain dietary pattern, has an impact," said Dr. Lenore Launer, a researcher at the National Institute on Aging. "More research would be needed to see if dietary patterns or taking the supplements earlier in the development of diseases like Alzheimer's would make a difference."
The NIH study follows one conducted by the University of Pennsylvania, which found no evidence of health benefits in people who take fish oil supplements.
Researchers in that study suggested the reason might have to do with molecular differences between fish oils found in actual fish, and those that are concentrated for supplemental pills.