A new study suggests that the consumption of walnuts, seeds andnuts, foods rich in ALA, can contribute to improve sustained attention and fluid intelligence, while decreasing symptoms of ADHD in adolescents.
The brain, consisting of 50-60% lipids, contains 40% omega-3 polyunsaturated fatty acids (PUFAs). The three main types of omega-3 are: docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and alpha-linolenic acid (ALA), the latter being the precursor of the previous ones. Omega-3 fatty acids are extremely important as they are essential components in the biotransformation of lipids in mammals.
DHA accounts for more than 40 % of total omega-3 polyunsaturated fatty acids in neural tissue, especially grey matter [2,3]. It is in the last stages of pregnancy and the first 18 months of life when DHA accumulates rapidly in the brain [1,3], being indispensable in both visual development and cognitive growth  in fetuses and newborns.
Nutrition during childhood is particularly important, as brain development is relatively rapid and it is during this period that nutrients help the brain to create new synaptic connections during learning processes at school and at home . While the structural components of the brain and the foundations of the basic systems of sensation and perception are fully developed when children reach kindergarten age, other systems, such as those related to memory, decision making and emotions, continue to develop well into childhood.
Consumption of omega-3 has been shown to improve learning, memory ability, cognitive well-being and blood flow in the brain. While omega-3 supplementation therapies are beneficial, well tolerated, and have very low risk , most researchers suggest that natural omega-3 intake be encouraged through foods such as fatty fish, nuts, and seeds.
Nuts and seeds, such as chia, are among the richest sources of alpha-linolenic acid (ALA), the precursor of EPA and longer-chain DHA [7,8]. Although there is controversy that ALA becomes a smaller proportion in EPA and DHA , clinical and animal studies have shown that ALA per se has positive effects on brain function and brain membrane plasticity [10,11].
Walnuts, nuts and seeds, in addition to omega-3, have a high content of fiber, vitamins, antioxidants, minerals, phytosterols, polyphenols and other bioactive compounds capable of improving brain health [12,13]. Indeed, it has been suggested that its components, in particular polyphenols, act synergistically with ALA by promoting brain health .
A recent study, published in The Lancet, shows an improvement in attention performance and fluid intelligence, and a reduction in ADHD symptoms for a group of adolescents who included walnuts, as a source of ALA, in their daily diet.
Although the relationship of dietary PUFAs to ADHD is still controversial, many studies have found that plasma PUFAs fractions are lower in children with ADHD. In addition, several trials have shown that, after a few weeks of supplementation with PUFAs, there is a positive response where ADHD symptoms tend to decrease [14, 15]. Symptoms of ADHD include deterioration in the development of attention in relation to structural and functional brain changes, specifically the deficit in sustained attention [14,15].
The findings of the study may not only help improve basic dietary recommendations for the adolescent population in order to ensure optimal intake of omega-3 polyunsaturated fatty acids for healthy brain development, but also show that regular consumption of omega-3 ALA through the intake of nuts and seeds can positively affect the neuropsychological development of adolescents, particularly in attention and fluid intelligence, in addition to reducing ADHD-related symptoms.
Although the results should be interpreted with caution, they are statistically significant if only the participants who adhered most to the intervention are considered. This means that regular consumption (> 3-4 servings per week) of nuts, nuts and seeds such as chia may result in improved cognitive function.
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