Researchers at the Pasqual Maragall Foundation's research center, the Barcelonaβeta Brain Research Center (BBRC), with the support of the “la Caixa” Foundation, have led one of the largest studies to date on the possible benefits of omega-3 fatty acid intake in people carrying the genotype that confers the highest risk of developing Alzheimer’s: APOE ε4/4. The research concludes that people in this at-risk group who consume more docosahexaenoic acid (DHA), a nutrient provided by blue fish, have greater cortical preservation in areas of the brain specifically affected by Alzheimer's disease and fewer microhemorrhages.
"To the benefits that we already knew that the consumption of fatty fish has in cardiovascular health, we can now say that it also provides greater brain resilience to Alzheimer's disease in people at higher genetic risk of developing it", says Dr. Aleix Sala, first author of the research, nutrition specialist and BBRC researcher. According to Sala, "the study opens up the possibility of improving the design of dietary interventions with DHA supplementation, focusing especially on people at higher risk of developing Alzheimer’s".
The study was published in The American Journal of Clinical Nutrition, and also involved researchers from the Hospital del Mar Institute for Medical Research; the CIBER on Fragility and Healthy Aging (CIBER-FES); the CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN); the VU University Medical Center in Amsterdam; and the Aiginition Hospital in Athens.
Role of omega-3s
Omega-3s are a family of fatty acids that have a distinctive chemical structural feature and are naturally present in certain foods of animal and plant origin. The type of fatty acid analyzed in this study is DHA, which is found mainly in fatty fish: tuna, sardines, salmon, anchovies, etc. This fatty acid is very abundant in the brain, is key to cognitive function, begins to build up from the third trimester of gestation, and is shown to have a lower presence in the brains of people with Alzheimer’s.
Humans are able to "make" this acid in our body, but we do it in a very inefficient way. The best way to ensure adequate levels of DHA is through the intake of fatty fish, as the omega-3 acids we get from vegetables such as walnuts and soy are of a different type.
Alfa Study Results
The research included a sample of 340 participants aged between 45 and 75, without cognitive impairments and from the BBRC Alfa Study, promoted by the “la Caixa” Foundation. These people went to the facilities of the Pasqual Maragall Foundation to undergo clinical tests, cognition, neuroimaging, and answer questionnaires on lifestyle habits, among others.
One of these questionnaires asked about the consumption of 166 foods, which have been used to quantify regular DHA intake. Based on participants’ responses, the researchers looked for associations between reported DHA consumption, cognition, the presence of brain microhemorrhages, and cortical thickness in brain regions that atrophy in Alzheimer’s, also taking into account the APOE genotype of each participant.
We all have the APOE gene and it can occur as a result of the combination of the Ɛ2, Ɛ3 and Ɛ4 alleles. In the case of Alzheimer’s disease, individuals with two Ɛ4 alleles have a higher risk of developing the disease.
Once the tests were done, the researchers did not observe any relationship between DHA consumption for foods, intake for nutrients or compounds and cognition, but they did detect the findings described in the brain structure. As Dr. Juan Domingo Gispert, head of the Neuroimaging group at the BBRC points out, “the results of this study are in line with others that show that people at greater genetic risk of developing Alzheimer's are those who benefit most from a healthy lifestyle, in this case, in terms of diet”.
There are currently no routine tests to determine the genetic predisposition of each person to develop Alzheimer's disease, as disclosing this information does not involve any clinical benefit. Alzheimer's does not yet have any treatment available to stop or prevent it, there are multiple risk factors that contribute to its development and, in no case, being a carrier of this genotype determines having the disease in a future.
Therefore, apart from the personal genetic load, Dr. Sala emphasizes that "although our findings between fatty fish and Alzheimer's disease affect only part of the population, we must continue to recommend regular consumption (two servings per week) of salmon, sardines or anchovies, among others, as it brings cardiovascular benefits to everyone”.
The next step for BBRC researchers will be to analyze biological markers of the consumption of up to 20 types of fatty acids in a larger population of Alfa Study participants, and to study their possible relationship with other biomarkers of Alzheimer's disease detected in the blood, cerebrospinal fluid, and through various tracers in Positron Emission Tomography (PET).