New research, presented at the Experimental Biology 2014 meeting, finds that low dietary intake of long-chain polyunsaturated fatty acids can predict cognitive decline.

Previous studies have shown that long-chain polyunsaturated fatty acids (PUFAs) are important for good brain health. Researchers from Tufts University in Medford, MA, wanted to see whether the PUFAs alpha-linolenic acid, eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) are risk factors for cognitive decline.

Conducting a longitudinal, observational study using the Boston Puerto Rican Health Study cohort, the researchers put 895 participants through "an intensive series of cognitive tests."

These included an attention test to repeat lists of numbers forward and backward, and tests of organization and planning that involved copying complex figures. The tests were repeated as part of a 2-year follow-up.

The participants also gave details of their dietary intake via questionnaires. The researchers found that the study group had low intake of omega-3 PUFAs. Only 27% of the participants were meeting the 2010 US Dietary Guidelines' recommended weekly intake of 8 or more ounces of seafood - primarily from eating canned tuna.

This dietary recommendation is to ensure that people receive an adequate amount - about 1,750 mg per week - of the long-chain omega-3 fatty acids EPA and DHA.

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Only 27% of the participants were meeting the 2010 US Dietary Guidelines' recommended weekly intake of 8 or more ounces of seafood.

The researchers found that the participants who were in the lowest four quintiles of EPA and DHA intake were the most likely to show signs of cognitive decline over the 2-year study period.

Lead author Tammy Scott, PhD, a scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, thinks that these results demonstrate a link between long-chain fatty acids are essential and good cognitive health but that many Americans do not have an adequate intake of PUFAs.

She says:

"While more research is needed to determine whether intake of fatty fish such as salmon, tuna and trout can help prevent against cognitive decline, our preliminary data support previous research showing that intake of these types of fish have health benefits."

Are PUFAs also beneficial for heart health?

In 2012, Medical News Today reported on a systematic review of 20 studies looking at the health benefits of PUFAs. Published in JAMA, that review - which included a total of 70,000 participants - found no statistically significant evidence that omega-3 PUFAs are linked to a lower risk of heart attack, stroke or premature death.

These findings were rebutted by the National Lipid Association, who told Medical News Today that "the totality of published evidence supports the use of both fish and fish oil supplementation to reduce the risk for cardiovascular disease and that this paper does not alter that perspective."

The results of the review also contradict the stance of the Food and Drug Administration (FDA) and some European regulators who approve omega-3 PUFAs for reducing cardiovascular risk.

Acknowledging that "the controversy stemming from the varying labeling indications causes confusion in everyday clinical practice about whether to use these agents for cardiovascular protection," the authors conceded that some groups may benefit from omega-PUFAs in the form of fish oil supplements.