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Omega-3s have a very good reputation in the medical world. Natural constituents of certain fats are said to be polyunsaturated due to their chemical structure, and essential because the human body cannot produce them. They therefore come exclusively from food, such as certain minerals and vitamins. For decades, they have been the subject of studies revealing their multiple roles in maintaining our health. Recently, U.S. researchers have shown that people who have high levels of DHA (a type of omega-3) in their blood are 49% less likely to develop Alzheimer’s disease than those who have lower levels. This discovery could revolutionize public health policies by preventing the risk of Alzheimer’s and potentially save billions in health care.
Omega-3s are part of certain vegetable oils and certain so-called “fatty” fish, but these bare sources are not equivalent. Plant products provide omega-3 alpha-linolenic acid (ALA). For their part, fatty fish (sardines, trout, mackerel, salmon, etc.) provide omega-3 EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Theoretically, we could only provide ALAs to the body, which is supposed to convert them to EPA and DHA. However, as the rate of conversion of ALA to DHA is very low to meet the new daily needs, DHA is considered essential, it must be brought through the diet.
Evidence that dietary factors may influence the risk of Alzheimer’s disease continues to accumulate. In addition, DHA is enriched in membrane phospholipids of the central nervous system and therefore plays a major role in mental and visual functions, especially in infants and adults. That’s why scientists have long suggested that it has a positive effect on maintaining mental health (depression, dementia, including Alzheimer’s disease).
Recently, a team from the Fatty Acid Research Institute (FARI), led by Aleix Sala-Vila, took an interest in this omega-3 and its link to Alzheimer’s disease. The authors found that supplemental dietary intake of omega-3 DHA could slow down the development of the disease and reduce the risk of developing it by almost half. This new study is published in the journal Nutrients.
Fatty fish against Alzheimer’s
To test their hypothesis, the researchers conducted a prospective observational study in the Framingham Offspring Cohort – comprising 1,490 participants without dementia, over the age of 65 – for an average of 7 years. They looked at the association of docosahexaenoic acid (DHA) with red blood cells with incident Alzheimer’s disease, while testing an interaction with the APOE gene allele 4 – which encodes a protein that helps carry cholesterol in the blood.
This study builds on the previous work of Aleix Sala-Vila, published in American Journal of Clinical Nutrition, in 2021. Indeed, he and his colleagues found that omega-3 levels in blood erythrocytes (or red blood cells) are very good predictors of mortality risk. Given the marginal synthesis again of DHA, the measurement of circulating or tissue levels of DHA is a valid biomarker of food intake of DHA, which helps to circumvent the uncertainties of self-reported dietary data.
In addition, Aleix Sala-Vila adds in a statement: « Having higher levels of these acids in the blood as a result of regular inclusion of fatty fish in the diet increases life expectancy by almost five years. ».
In the present study, the team found that the risk of developing Alzheimer’s disease with a high blood level of DHA (6.1%) was lower than 49% compared to a lower level (3.8%). In addition, the authors estimated that an increase in erythrocyte DHA from the first to the fifth trimester of the study provided approximately 4.7 additional years of life without Alzheimer’s disease. This latest conclusion confirms that of 2021.
Omega-3s against genetic risk factors
As a result, the authors established a definite link between a genetic factor, DHA, and the risk of Alzheimer’s disease. It is important to specify for the first time instead of the vast majority of cases of Alzheimer’s disease, which corresponds to patients for whom there is a multifactorial determinism, and includes among the early forms. The genetic part of this determinism is important and is represented by various risk factors. The first and foremost of these factors is allele 4 of the APOE gene (APOE4) encoding apolipoprotein E, which helps carry blood cholesterol.
The APOE gene exists in three “forms” called the E2, E3 (most common) and E4 alleles. While carriers of the E2 allele have a lower risk of developing Alzheimer’s disease, carriers of at least one E4 allele have a higher risk. The importance of this factor is therefore greater, both in terms of the strength of the associated risk and the significant frequency. In fact, almost 10% of carriers of an APOE4 allele who have reached the age of 75 develop the disease, compared with 33% of homozygous carriers – carriers of the same allele twice – APOE4 / E4 of the same age. At the age of 85, these figures are close to 30% and 70%, respectively, for heterozygotes – carriers of two different alleles – APOE3 / E4 and for homozygotes APOE4 / E4. In the general Caucasian population over the age of 54, the proportion of carriers of an APOE4 allele is 24%, and the homozygous APOE4 / E4 is 2%. The importance of this genetic risk factor for the individuals concerned, but also for the general population, justifies the research programs in therapeutic prevention.
Consequently, the researchers noted that increased consumption of DHA could reduce the risk of developing Alzheimer’s disease, especially in people with the APOE4 allele, suggesting that they may benefit from more level levels. Higher DHA than non-carriers.
This finding, which is consistent with a growing experimental research base, is changing the outlook for public health and prevention, as well as health care costs. The authors concluding in the study: « Given that the estimated health care spending in 2021 for all patients with Alzheimer’s disease or other forms of dementia is $ 355 billion in the United States (excluding care provided by the United States). family members and other unpaid people), the whole rental strategy for delaying the onset of Alzheimer’s disease is of major interest to public health. ». They added: “ Delaying Alzheimer’s disease for 5 years leads to an additional 2.7 years of life and an additional 4.8 years without Alzheimer’s disease, knowing that an individual who has contracted Alzheimer’s disease costs more than $ 500,000 in care ».