By Matt McMillen
MONDAY, February 27, 2012 (Health.com) — Eating a diet rich in omega-3 fatty acids—healthy fats found in abundance in oily fish such as salmon—may protect against premature aging of the brain and memory problems in late middle age, according to a study published today in the journal Neurology.
Fish has long had a reputation as a brain food. The new study, however, is the first to link blood levels of omega-3s with brain shrinkage, mild memory loss, and declines in cognitive function, all of which are associated with a higher risk of developing Alzheimer's disease and other forms of dementia.
The study included 1,575 people between the ages of 58 and 76 who underwent MRI brain scans, blood work, and various mental-function tests. Compared to those with the highest blood levels of omega-3s, men and women with the lowest levels had smaller brain volumes and performed more poorly on tests of visual memory and abstract reasoning.
"The lower the omega-3s, the poorer the performance," says lead author Zaldy Tan, MD, an Alzheimer's researcher at the University of California, Los Angeles. "We factored in the participants' age, gender, education, body mass index, smoking, et cetera—and even after that, the relationship was still there."
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Previous studies have found a similar link between omega-3s and dementia, but those relied on food surveys in which the participants were asked to recall what they ate over a given week or month, a method that can be inaccurate. Blood tests, on the other hand, show precisely how much of the healthy fats a person's body has absorbed.
"This is the very first time this has been correlated, so this is very exciting," says Gisele Wolf-Klein, MD, the director of geriatric education at the North Shore–LIJ Health System, in New Hyde Park, N.Y., who was not involved in the research. "This study will generate a lot of further research."
A smaller brain isn't necessarily cause for concern, since the brain naturally shrinks with age. But the study participants with the lowest levels of omega-3s had brain volumes typical of people two years older, Tan says. On cogntive tests, meanwhile, their average scores matched those of people nearly three years older.
In addition, people with low levels of omega-3s also tended to have greater buildup of white matter in their brains. These so-called white matter hyperintensities have been linked to a higher risk of dementia and stroke.
The findings don't mean that people should stock up on fish or fish-oil supplements, the other main source of omega-3s. "Don't read this study and run to the store to get omega-3 tablets," Wolf-Klein says. "This was not an intervention study that can be translated into clinical recommendations."
Federal dietary guidelines currently recommend eight ounces of seafood per week for the prevention of heart disease. (Flax seeds and walnuts also are excellent sources of omega-3s.) Tan says that intake is "probably adequate" for most people, although he notes that research has yet to determine what constitutes a normal, healthy amount of omega-3s in the bloodstream.
"Will supplements get you to where you need to be? We don't know. We don't have established recommendations, so we don't know what to aim for," he says. "But what's good for the heart appears to be good for the brain as well."
Brian Appleby, MD, a psychiatrist at the Cleveland Clinic's Lou Ruvo Center for Brain Health, says that observation is the study's biggest take-home message.
"Cardiovascular health is linked to cognitive health," says Appleby, who did not participate in the research. "This study strengthens the need to tell people that."