PhotoConsumers can be excused if they're frustrated by all the competing studies. This thing is good for you, one study declares. Not it's not, declares another.

Well, here we go again.

No less an authority than the National Institutes of Health (NIH) has declared that a diet high in omega-3 fatty acids has not been shown to slow cognitive decline in older people, based on a large five-year study.

“Contrary to popular belief, we didn’t see any benefit of omega-3 supplements for stopping cognitive decline,” said Emily Chew, M.D., deputy director of the Division of Epidemiology and Clinical Applications and deputy clinical director at the National Eye Institute (NEI), part of NIH.

Part of an eye study

The study began when researchers were testing whether a combination of nutritional supplements could slow age-related macular degeneration (AMD), a major cause of vision loss among older Americans. It later added omega-3 and found it made no difference, either in AMD progression or in warding off dementia.

We reported as recently as May on a University of Illinois study that found omega-3 may help aging minds stay sharp. That study found that older adults who consumed a diet with lots of omega-3s did better than their peers on tests measuring cognitive flexibility – the ability to efficiently switch between tasks or areas of focus.

Brain scans also revealed they had a bigger anterior cingulate cortex, the part of the brain that contributes to cognitive flexibility.

Health claims

Health claims associated with omega-3 have been the source of controversy since the Food and Drug Administration (FDA) approved them in 2004. Back in 2007, the Center for Science in the Public Interest urged the FDA to stop seven egg producers from promoting omega-3 content in their eggs as a source of heart health.

The NIH researchers say they aren't prepared to rule out omega-3's contribution to brain health, just that their test didn't uncover it. That's not to say that future trials might not prove that connection.

Alzheimer’s disease, which is the most common cause of dementia and affects as many as 5.1 million Americans age 65 and older in the U.S., is predicted to explode over the next four decades. Some research has examined the potential benefits of DHA, a component of omega-3, for Alzheimer’s.

NIH says animal studies found that DHA reduces beta-amyloid plaques, abnormal protein deposits in the brain that are a hallmark of Alzheimer’s. However, it notes a clinical trial of DHA showed no impact on people with mild to moderate Alzheimer’s disease.

“The data adds to our efforts to understand the relationship between dietary components and Alzheimer’s disease and cognitive decline,” said Lenore Launer, Ph.D. senior investigator in the Laboratory of Epidemiology and Population Science at the National Institute on Aging. “It may be, for example, that the timing of nutrients, or consuming them in a certain dietary pattern, has an impact.”

She says more research might reveal if dietary patterns or taking the supplements earlier in the development of diseases like Alzheimer’s would make a difference.

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