Eating foods like fish, chicken, nuts and salad dressings – all high in the heart-healthy fats known as omega-3’s – are linked to lower blood levels of beta-amyloid, a toxic protein that builds up in the brains of those with Alzheimer’s disease. The findings, reported in the medical journal Neurology, add to a growing body of evidence linking dietary omega-3s to a reduced risk for Alzheimer’s.
“While it’s not easy to measure the level of beta-amyloid deposits in the brain in this type of study, it is relatively easy to measure the levels of beta-amyloid in the blood, which, to a certain degree, relates to the level in the brain,” said study author Dr. Nikolaos Scarmeas of Columbia University Medical Center in New York.
Increasing evidence suggests that diet may play an important role in preventing or delaying the onset of Alzheimer’s disease. Other studies have shown that a Mediterranean-style diet, rich in fish, fresh fruits and vegetables and olive oils, for example, is associated with a lower risk of Alzheimer’s and memory problems.
For the current study, researchers looked at 1,219 seniors, all of whom were free of dementia. They completed surveys about what they ate for an average of 1.2 years before their blood was tested for beta-amyloid.
The scientists looked at a variety of nutrients in addition to omega-3s. They include saturated fats (the kinds found in fatty meats), omega-6s (polyunsaturated fats found in many vegetable oils), vitamins C and E and beta-carotene (antioxidants), and vitamin B12 and folate (B vitamins linked to nervous system health).
The more omega-3s someone ate, the lower their blood levels of beta-amyloid. Eating just 1 gram of omega-3s per day – equal to the amount found in just half a salmon fillet per week – reduced blood beta-amyloid levels by 20 to 30 percent compared to those who ate less omega-3s. The benefits persisted, even after controlling for other known Alzheimer’s risk factors like age, education levels, calories consumed and the presence of the APOE-E4 gene. Other nutrients did not have a similar effect on beta-amyloid levels.
In the study, those who had the highest omega-3 blood levels tended to get the nutrient from salad dressings, fish, poultry, margarine and nuts.
High levels of beta-amyloid in the brain have been linked to formation of brain plaques, a hallmark of Alzheimer’s. The more plaque in the brain, in general, the worse someone’s memory. While the relationship between beta-amyloid blood levels and brain levels remains uncertain, studies suggest that high levels of beta-amyloid in the brain will be linked, over time, to high levels in the blood. Conversely, low blood levels of the toxic protein are thought to be linked to low brain levels.
Animal studies, for example, consistently show that animals fed diets rich in omega-3s have reduced levels of beta-amyloid in the brain and fewer plaques than those fed normal diets. Other scientists have shown that taking fish oil supplements rich in omega-3s may be associated with a reduced Alzheimer’s risk and a more robust brain.
Sources: Y. Gu, N. Schupf, S.A. Cosentino, et al: “Nutrient Intake and Plasma Beta-Amyloid.” Neurology Vol 78: 1:1, 2012.