Eating foods such as chicken, fish and nuts may help lower blood levels of a protein strongly associated with Alzheimer's disease and memory problems, according to new research.
In the Columbia University study, people who consumed diets rich in omega-3 fatty acids had significantly lower levels of a protein called beta-amyloid in their blood than those who did not consume as much of the nutrient.
According to the research, eating one more gram of omega-3s than average per week was associated with 20 to 30 percent lower levels of beta-amyloid. One gram is approximately equal to half a fillet of salmon.
However, study author Dr. Nikolaos Scarmeas, a neurologist at Columbia University Medical Center in New York and a member of the American Academy of Neurology, recommended not focusing on eating particular quantities of omega-3s, but rather, simply incorporating as much of the nutrient into one’s diet as possible.
"It was a continuous association. More and more intake of omega-3s was associated with lower and lower levels of beta-amyloid in the blood. There was no threshold effect," Scarmeas said.
The association between omega-3 consumption and beta-amyloid was unaffected by whether or not a person took supplements - meaning if two people consumed the same amount of omega-3s, one through food and the other through supplements, the person who consumed more omega-3 rich foods typically had lower blood levels of beta-amyloid.
It is believed that the build-up of beta-amyloid in the brain, not the blood, is a precursor for Alzheimer's. However, past studies have indicated there may be a relationship between blood levels and brain levels of the protein.
“There is complex, conflicting literature; we do not understand very well biologically how levels of beta-amyloid in the blood, brain and spinal fluid are related exactly,” Scarmeas said. "In some studies, higher levels of beta-amyloid in the blood relate to higher levels of beta-amyloid in the brain. Other studies have suggested the opposite."
Scarmeas added that his own lab had observed that people with higher blood levels of beta-amyloid were more likely to develop dementia, while people with lower levels tended not to.
“Some of these [participants] have already been followed up on,” he said. “We know those with lower levels of beta-amyloid in the blood were less likely to develop dementia.”
The beneficial impact of omega-3 on brain health would fall in line with past studies of the nutrient, according to Scarmeas. Omega-3s have long been associated with positive benefits for memory and cognition.
Scarmeas speculated that omega-3s may be able to reduce oxidative stress on the brain and the resulting vascular damage, or even have some kind of impact on beta-amyloid in the brain. Though, there is not enough support yet to suggest the nutrient and protein are directly related, he added.
"Previous studies have suggested that omega-3s and other aspects of diet may be related to brain function," he said. "Here we demonstrate one possible mechanism could be through amyloid, the main biological mechanism that relates to Alzheimer's disease. There have been animal studies suggesting omega-3s could relate to amyloid brain biology. We've demonstrated this association may also be present in humans."
The study was published Wednesday in the journal Neurology.