Alzheimer's disease, reduced risk with higher blood concentrations of DHA

 Having high amounts of DHA (docosahexaenoic acid) in the blood may protect againstAlzheimer's disease. The news comes from the pages of the scientific journal Nutrients, where a team of researchers led by William S. Harris, an expert from the Fatty Acid Research Institute (FARI) and the Sanford School of Medicine in Sioux Falls, USA, published a new study on the subject.

According to data compiled by Harris and collaborators, increasing intake of this omega-3 fatty acid could be particularly helpful for those who carry the APOE- ε4 gene, themselves at greater risk of developing Alzheimer's.   

Alzheimer's disease and DHA: the link 

According to Airalzh (the Italian Alzheimer Research Association Onlus), Italy ranks eighth in the list of countries with the highest number of people with Alzheimer's disease. The situation is set to worsen worldwide: according to estimates, 1 in 85 people will be living with this neurodegenerative disease by 2050.Diet can significantly influence Alzheimer's risk. In particular, DHA, an Omega 3 abundant in the central nervous system normally taken with food, can improve several parameters altered by this disease, such as the formation of aggregates that impair neuron function, cerebral glucose metabolism, and nerve cell inflammation. As early as 2006, a study published in Archives of Neurology associated plasma DHA levels with reduced risk of dementia from any cause. 

Its authors had estimated that, on average, taking 180 mg of DHA per day or consuming 3 servings of fish per week can reduce the risk of dementia by 47 percent compared with that run by people with low plasma DHA levels. Not only that, previously published studies have also shown an association between DHA levels in red blood cells (a parameter that better reflects long-term intake of DHA than its levels in plasma) and cognitiveperformance and brain volume. 

The new data

In this new research, Harris and collaborators divided the 1,490 individuals involved in the study (men and women aged 65 and older, none of whom had yet been diagnosed with dementia) into five groups based on the levels of DHA in their red blood cells. The participants' health was monitored for an average of 7.2 years, during which neurocognitive tests were also conducted. The data collected showed that:

• when DHA in red blood cells exceeds 6.1%, the risk of Alzheimer's disease is reduced by 49% compared to when DHA in red blood cells is less than 3.8%;
• Going from a DHA concentration below 3.8% to a concentration above 6.1% could delay the onset of Alzheimer's by 4.7 years;
• the association between DHA levels in red blood cells and dementia risk is greater in those who already run a higher risk of developing Alzheimer's because they carry the APOE-ε4 gene.

"Our results," the researchers conclude, "suggest that increasing DHA intake could be a safe and cost-effective strategy to prevent Alzheimer's disease in specific populations."   

How to increase the intake of DHA 

In food, Omega 3s may be present in the form of DHA, EPA (eicosapentaenoic acid, the other biologically active Omega 3) or their precursor, alpha-linolenic acid (ALA). 

Unfortunately, the human body's ability to synthesize DHA from ALA is poor; therefore, the best way to increase intake is to enrich one's diet with foods that abound in this Omega 3, such as salmon, sardines, and sardines. In cases of increased+to high requirements-such as in individuals carrying the APOE-ε4 gene, in whom DHA levels are lower than average-it may be useful to resort to the use of dietary supplements, even more so in light of the fact that the European Food Safety Authority (EFSA) authorizes the use of the claim that "DHA contributes to normal brain function." Beware, however: EFSA itself stresses that to exert its brain benefits, DHA must be taken in doses of at least 250 mg per day. 

Sources: Sala-Vila A et al. Red Blood Cell DHA Is Inversely Associated with Risk of Incident Alzheimer's Disease and All-Cause Dementia: Framingham Offspring Study. Nutrients. 2022. June 9;14(12): 2408. doi: 10.3390/nu14122408 Airalzh. Numbers. https://cutt.ly/ZJ3fQaV. 06/13/2022 Schaefer EJ et al. Plasma phosphatidylcholine docosahexaenoic acid content and risk of dementia and Alzheimer disease: the Framingham Heart Study. Arch Neurol. 2006 Nov;63(11):1545-50. doi: 10.1001/archneur.63.11.1545 Efsa. EU Register of nutrition and health claims made on foods. 13/06/2022