Two new studies, one conducted in the U.S. and the other in Spain, came to similar conclusions but unfortunately that’s not good news: both suggest that omega-3 fatty acids may not prevent cognitive decline. Despite this unhappy result, the researchers still recommend each of us continue to include fish and nuts in our diets.

What Are Omega-3s?

Omega-3 fatty acids, also known as polyunsaturated fatty acids, are necessary to maintain your health but the body does not produce them on its own. In fact, those who are deficient in omega-3 fatty acid develop symptoms, including fatigue, poor memory, dry skin, heart problems, mood swings, depression, and poor circulation. Eating correctly is one way to get the appropriate amount each day. High amounts of omega-3s can be found in fatty fish and some nuts, including salmon, tuna, halibut, seafood, algae, walnuts, and butternuts.

Omega-3 fatty acids are highly concentrated in the brain and appear to be crucial for cognitive function (memory and performance) as well as behavioral function. Scientists have found that mothers who do not provide enough omega-3 fatty acids to their fetus during pregnancy may be at risk of delivering a baby who has or develops vision and nerve problems. Omega-3 fatty acids may reduce inflammation and help lower risk of chronic diseases, such as cancer, arthritis, and even heart disease. For these reasons, the American Heart Association recommends eating fish at least two times a week.

American Study

Researchers at the University of Iowa conducted a study involving 2,157 participants, all women between the ages of 65 and 80 who were enrolled in the Women's Health Initiative clinical trials of hormone therapy. Before the start of the study, researchers analyzed results of blood tests to measure the amount of omega-3s. Then, the women were given annual tests of thinking and memory skills for an average of six years. Among these women, some showed high levels of omega-3s in their blood, while others showed low levels, but the researchers found no difference in memory test scores at the time of the first test. Additionally, no differences emerged in how quickly their thinking skills declined over time.

"There has been a lot of interest in omega-3s as a way to prevent or delay cognitive decline, but unfortunately our study did not find a protective effect in older women," study author Eric Ammann, of the University of Iowa, stated in a press release. "However, we do not recommend that people change their diet based on these results. We know that fish and nuts can be healthy alternatives to red meat and full-fat dairy products, which are high in saturated fats."

Spanish Study

In their efforts to update and summarize any evidence related to the effect of diet and nutritional factors on the risk of Alzheimer's disease and cognitive aging, researchers conducted a search of Medline and Web of Knowledge for epidemiological and clinical studies published between Jan. 2000 and Feb. 2013. One criteria for inclusion in their study was use of combinations of the following keywords: "Alzheimer's disease," "mild cognitive impairment," "cognitive function," "dietary factors," "omega-3," "antioxidants," "B vitamins," "dietary patterns," and "Mediterranean diet."

What did they find? Data from randomized controlled trials did not show a consistent effect, even if data from observational studies pointed to a protective role for certain nutrients, such as omega-3 fatty acids, antioxidants, B vitamins, and a Mediterranean diet. In other words, true scientific evidence is lacking.

“Whether confounding factors such as age, disease stage, other dietary components, cooking processes, and other methodological issues explain the divergent results remains to be established,” the authors wrote in their study.

Although many hoped a diet rich in omega-3 fatty acids might be a way of preventing Alzheimer's disease, unfortunately the research fails to provide evidence supporting such claims. Despite such disheartening results, the fact remains that omega-3s are clearly important to developing brains as discovered in a recent study conducted by British researchers; and omega-3s remain important for ongoing brain function in adults. While continuing to eat our fish and nuts, we can all search for some other ways to save our brains.

Sources: Otaegui-Arrazola A, Amiano P, Elbusto A, et al. Diet, cognition, and Alzheimer's disease: food for thought. European Journal of Nutrition. 2013.

Ammann EM, Pottala JV, Harris WS, et al. Omega-3 fatty acids and domain-specific cognitive aging. Neurology. 2012.