Skimping on omega-3 fatty acids -- nutrients found in certain oils, beans and seafood -- may take a toll on brain volume and memory, according to a new study. In it, researchers used MRIs and other markers to help show that adults with lower levels of omega-3 may actually have smaller brains, as well as certain signs of cognitive impairment.
In the study, published Monday in the journal Neurology, researchers looked at the levels of omega-3s in the red blood cells of more than 1,500 dementia-free adults, whose average age was 67. The researchers also conducted MRI brain scans and administered tests measuring cognitive function.
They found that participants whose levels of DHA -- a particular type of omega-3 -- were low enough to put them in the bottom 25 percent had substantially lower brain volume than those with higher levels of DHA. The difference was equivalent to approximately two years of structural brain aging.
In addition, participants in the bottom quartile of overall omega-3 levels performed worse on tests measuring visual memory, abstract thinking and executive function, which includes processes such as organizing, planning and recalling details.
"What does it mean? Well, the areas of the brain that are affected are more indicative of vascular disease," said Dr. Zaldy Tan of the Easton Center for Alzheimer's Disease Research at UCLA and one of the study's authors. He explained that the current study does not make clear what constitutes normal levels of red blood cell fatty acids.
"It fits in with other studies looking at the beneficial vascular effects," he added.
Indeed, the authors reference past research suggesting that omega-3s can reduce blood pressure and inflammation, as well as lower triglyceride levels. (According to the American Heart Association, triglycerides, or "blood fats," are a key measure of metabolic health. High levels of triglycerides are linked with heart disease and diabetes, among other things.)
Many such vascular risk factors have been linked with an increased risk of developing dementia, prompting the authors to write that omega-3s "may delay cognitive and structural brain aging by some combination of these mechanisms."
"I think we can say that omega-3s are important for brain function, specifically DHA," said Elaine Pelc, who is a clinical dietitian at the University of Maryland Medical Center and was not associated with the study.
"DHA is actively present in the brain, and higher intakes are associated with memory, brain function and cognition," she added.
Pelc explained that the most beneficial omega-3s are found in cold-water fatty fish, including salmon, makerel, halibut, sardines, tuna and herring. Alpha-linolenic acid or ALA -- another omega-3 -- is found in sources like flaxseeds and flaxseed oil, canola oil, soybeans and walnuts.
Because of the metabolic benefits of omega-3 consumption, the American Heart Association recommends eating at least two, 3.5-ounce servings of cooked (or three-quarters cup flaked) fish per week, adding that people with coronary artery disease may want to talk with their doctor about adding supplements.
"A lot of cardiologists routinely recommend that patients take fish oils, because they seem to confer beneficial effects to the heart," Tan said. "The question from this study is, can this benefit your brain at all?"