Omega-3 intake linked to lower levels of protein associated with Alzheimer’s

A diet rich in omega-3 fatty acids might help slow the surge of new Alzheimer’s disease cases expected in the next few decades as the nation’s elderly population grows, a study suggests.

People who consume the most omega-3 have the lowest blood levels of beta-amyloid, a protein fragment associated with Alzheimer’s, according to the study published online May 2 in Neurology. But the cause of this relationship is not yet clear, said first study author Yian Gu, PhD.

The most common sources of omega-3 among study participants were fish, margarine, nuts, poultry and salad dressing.

“This is not a clinical trial,” said Gu, associate research scientist at Columbia University Medical Center in New York. “It’s an epidemiological study, so we have to be very cautious about making recommendations [for health professionals based on the results]. But physicians should stay tuned and see what we find in our follow-up study.”

An estimated 5.4 million Americans, including 200,000 people younger than 65, have Alzheimer’s disease, according to the Alzheimer’s Assn. By 2050, as many as 13.2 million people could have the condition, which is the leading cause of dementia. The projected uptick is largely due to the growing elderly population, which is expected to more than double in the next 40 years, the U.S. Census Bureau said.

Researchers for the Neurology study examined the health and diet of 1,219 people 65 and older who lived in northern Manhattan in New York and did not have dementia. The individuals were part of the Washington Heights/Hamilton Heights Columbia Aging Project.

Participants reported their average food consumption during the past year by completing the 61-item version of Willett’s semiquantitative food frequency questionnaire. Researchers focused on 10 nutrients that are most commonly thought to be related to Alzheimer’s disease or cognitive function. Those nutrients are: omega-3, omega-6 fatty acids, monounsaturated fatty acids, saturated fatty acids, beta-carotene, vitamin C, vitamin E, vitamin B12, folate and vitamin D (link).

Blood samples were collected from participants an average of one year after the dietary survey and were assessed for their level of beta-amyloid 40 and 42. In Alzheimer’s disease, those protein fragments are thought to accumulate in the brain and form plaque, Alzheimer’s experts say. The plaque contributes to nerve cell damage in the brain and leads to the symptoms of Alzheimer’s.

Changes in beta-amyloid 42 levels in a person’s blood over a period of time might reflect the presence of beta-amyloid in his or her brain, the study said.

Data show that consuming one gram of omega-3 fatty acids each day (equivalent to eating about half a filet of salmon) is associated with 20% to 30% lower blood beta-amyloid levels, according to the study authors.

There was no association between beta-amyloid levels and the other studied nutrients.