The Importance of DHA and AA as Neuroprotective Nutrients
The brain is the most complex organ in the human body, and controls breathing, emotion, hunger, memory, motor skills, temperature, thought, touch and vision. Furthermore, it controls every process that regulates our body.
It has become apparent that certain nutrients are required to safeguard various aspects of brain health, including mental performance, psychological function and the working of the nervous system.
What are Docosahexaenoic and Arachidonic Acids?
Docosahexaenoic acid (DHA) is a long-chain polyunsaturated omega-3 fatty acid that is present throughout the body. It belongs to a group of unsaturated fats that is required to maintain a healthy heart and blood circulation. It is a major structural fat in the brain and also a key component of the heart. DHA is not produced by the body endogenously in adequate amounts, therefore, it needs to be consumed from dietary or supplement sources. Oily fish, such as sardines, salmon and mackerel, egg yolk, chia, flax and hemp seeds are some predominant sources of DHA.
Arachidonic acid (AA) is a long-chain polyunsaturated omega-6 fatty acid that is an essential component of biological cell membranes. It is required for the functioning of all cells, especially in the nervous system, skeletal muscle, and the immune system. Similarly, to DHA, AA is not produced endogenously in adequate amounts and needs to be consumed from dietary or supplement sources. AA can be found in foods such as meat, eggs, fish, milk, and algae.
The Role of DHA and AA in Brain Health
A review has been published in Nutrients investigating the role of DHA and AA in neurogenesis and brain development. DHA and AA are both required for brain development in infants. DHA in particular has been shown to be important for infant brain, eye and nervous system development and has been shown to support long-term heart health. Furthermore, DHA and AA are important throughout pregnancy, especially in the third trimester and throughout the first two years of life when significant brain growth occurs.
DHA and AA in Early Brain Development
The human brain begins to develop with the formation of the primitive neural tube during the first four weeks of gestation. Studies show that during the last trimester of pregnancy and the first two years of life, a rapid build-up of both DHA and AA happens in the developing brain. Furthermore, during the second year of life, brain growth continues rapidly and the grey matter of the brain, which accumulates the greatest amount of DHA, increases in volume until the fifth year of life.
Research has shown that supplementation of DHA during childhood has long-lasting effects on brain structure, function, and neurochemical concentrations.
Dr Verónica Sambra, from the Faculty of Medicine, University of Chile, Santiago, Chile, and lead author concluded that 'the relevance of DHA and AA during the first months of life is widely accepted because these [nutrients] play a fundamental role in neural development'.
DHA and AA in Dementia
Dr Sambra also analysed the neurological role of DHA and AA in a context of age-related neurodegenerative disease prevention due to their role in neuroprotection against neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease.
Clinical trials in healthy people have shown that DHA supplementation preserves cognitive abilities, such as learning, memory and verbal fluency.
Mechanisms have been described by which DHA could exert a neuroprotective effect and research shows that populations with a higher intake of DHA show a lower risk of developing cognitive impairment or Alzheimer's disease. Further research is required into the dose-response relationship for DHA in the treatment of patients with Alzheimer's disease and Parkinson's disease since the review concludes that the use of DHA could be an alternative or a complement to the pharmacological treatment of these diseases in the early stages.
However, even though DHA in advanced stages of life is associated with neuroprotective effects, both in healthy humans and in patients with Alzheimer's disease and Parkinson's disease, the role of AA in these disorders is still controversial. Hence Dr Sambra advices that future research should be directed towards understanding the role of AA in ageing and neurodegenerative pathologies.
Both DHA and AA may be selective and promising nutrients for the prevention of premature brain ageing and its associated pathologies. There is an unmet need to increase our knowledge of the bioavailability, pharmacodynamics, pharmacokinetic and metabolic effects of DHA and AA and towards the development of personalised medicine to garner neuroprotection throughout the life cycle.
Sambra V, et al (2021). Docosahexaenoic and Arachidonic Acids as Neuroprotective Nutrients throughout the Life Cycle. Nutrients. Mar; 13(3): 986. Available at https://doi.org/ 10.3390/nu13030986.