In developing countries, millions of young children suffer from nutritional deficiencies and frequent infections. There is now a large and increasing body of evidence to indicate that nutrition and health affect children’s cognitive, motor, and behavioral development, both pre-and postnatally.
The situation is further complicated in those children who suffer from nutritional deficiencies. Infections usually come from poor socio-cultural environments and suffer from a myriad of deprivations and disadvantages that could themselves be detrimental to intellectual and behavioral development.
Cognition represents a complex set of higher mental functions subserved by the brain and includes attention, memory, thinking, learning, and perception. Cognitive development is influenced by many factors, including nutrition.
There is an increasing body of literature that suggests a connection between improved nutrition and optimal brain function. Nutrients provide building blocks that play a critical role in cell proliferation, DNA synthesis, neurotransmitter, and hormone metabolism, and are important constituents of enzyme systems in the brain. Brain development is faster in the early years of life compared to the rest of the body. It may make it more vulnerable to dietary deficiencies.
There is a link between nutritional intake in pregnancy and childhood and children’s cognitive development.
Let us discuss individual micronutrients and single aspects of diet and the role of nutrition in neurocognitive development. The understanding of the functional and structural development of the human brain has emerged from a range of methodologies.
Brain development is a temporally extended and complex process, with different parts and functions of the brain developing at different times:-
By 5 weeks after conception in humans, the anterior-posterior and dorsal-ventral axes of the neural tube have already developed.
The cortical plate and some inter-neuronal connections form from 8 to 16 weeks of gestation.
From 24 weeks of gestation until the prenatal period, the neurons in the cortical plate die and are replaced by more mature cortical neurons.
From 34 weeks post-conception until 2 years of age, peak synapse development, and significant brain growth occurs.
At preschool age, synaptic density has reached the adult level. The myelination of some parts of the brain (particularly those that control higher cognitive functions, such as the frontal lobes) continues well into adolescence.
The maturation of specific brain areas during childhood is associated with the development of specific cognitive functions such as language, reading, and memory.
The maturation of specific brain areas during childhood links with the development of specific cognitive functions such as language, reading, and memory.
The development of some subcortical structures including the basal ganglia, amygdala, and hippocampus (which are also in some mediating higher cognitive functions, including memory, executive functions, and emotion) also continues until late adolescence.
The research evidence shows that cognitive development is has a link with micro and macro-anatomical changes that take place throughout childhood. It is has the influence of environmental factors including nutrition.
Nutrition is one of the most salient environmental factors, and that nutrition can have a direct effect on gene expression.
The timing of nutritional deficiencies can significantly affect brain development. For example, it is folic acid deficiency results in malformation, called a neural tube defect. Since rapid brain growth occurs during the first 2 years of life. So we must be alerting particularly sensitive to deficiencies in the diet.
NUTRIENTS THAT EFFECT COGNITIVE DEVELOPMENT
- Omega-3 fatty acids:-
Essential fatty acids play a central functional role in brain tissue. They are not only the basic components of neuronal membranes, but they modulate membrane fluidity and volume and thereby influence receptor and enzyme activities in addition to affecting ion channels. Essential fatty acids are also precursors for active mediators that play a key role in inflammation and immune reaction.
HOW IT WORKS:-
The effect of essential fatty acids, particularly long-chain polyunsaturated fatty acids (LCPUFA), on cognitive brain development. Of the human brain’s dry weight 60% contains of lipids, of which 20% are docosahexaenoic acid (which is an omega3 fatty acid) and arachidonic acid (an omega-6 fatty acid). The supply of long-chain polyunsaturated fatty acids from food, especially the omega-3 fatty acids, including docosahexaenoic acid and eicosapentaenoic acid is frequently inadequate for children as well as for adults.
They promote neuronally and dendrite spine growth and synaptic membrane synthesis, and hence influence signal processing, and neural transmission.
Also, essential fatty acids regulate gene expression in the brain.
It has been suggested that the fast growth of the human cerebral cortex during the last two million years was strongly related to the balanced dietary intake of long-chain polyunsaturated fatty acids with an equal ratio of omega-6 and omega-3 fatty acids in the diet.
The docosahexaenoic acid component is to be one of the main reasons why breast milk may improve the cognitive performance of children. Humans can endogenously synthesize docosahexaenoic acid from precursor α-linolenic acid. However, the conversion rate varies according to genetically determined polymorphisms in two genes.
Vitamin B12, folic acid, and choline:-
There has been an increasing interest in the association between vitamin B12, folic acid, choline metabolism, and cognitive development.
HOW IT EFFECTS:
Folate affects neural stem cell proliferation and differentiation, decreases apoptosis, alters Deoxyribonucleic acid biosynthesis, and has an important role in homocysteine and S-adenosylmethionine biosynthesis.
S-adenosylmethionine is one of the main methyl donors in different metabolic methylation reactions, including Deoxyribonucleic acid methylation. Therefore, choline and folate deficiency may result in Deoxyribonucleic acid hypomethylation, thereby altering gene transcription.
Vitamin B12 has a role in axon myelination that is important for impulse conduction from cell to cell, and it also protects neurons from degeneration.
Vitamin B12 may also alter the synthesis of different cytokines, growth factors, and oxidative energy metabolites such as lactic acid.
Those adolescents who consumed a macrobiotic diet until 6 years of age had lower levels of fluid intelligence, spatial ability, and short term memory.
Vitamin B12 affects some cognitive functions only if the person is severely deficient, as can be seen in vegetarian mothers and their children.
Zinc plays an important role in the metabolism of the retina and the lens of the eye. Zinc is an essential constituent of many enzymes and so is necessary for the regulation of much of the body’s metabolism. Zinc ions are present in the enzyme superoxide dismutase, which plays an important role in scavenging superoxide radicals. The zinc concentration in the retina and choroid is normally one of the highest levels in the body.
HOW IT EFFECTS:
- zinc is a cofactor for more than 200 enzymes that regulate diverse metabolic activities in the body including protein, DNA, and RNA synthesis.
- It plays a role in neurogenesis, maturation, and migration of neurons and synapse formation.
- Also, zinc is in high concentrations in synaptic vesicles of hippocampal neurons and seems to modulate some neurotransmitters including glutamate and gamma-aminobutyric acid.
- Zinc supplementation has a positive effect on the immune status of infants and may prevent congenital malformations.
One of the most common nutritional deficiencies in both developing and developed countries is iron deficiency. In some parts of the world, such as in Sub-Saharan Africa and South-East Asia, the prevalence is more than 40%. Did you knew that iron is involved with different enzyme systems in the brain, including the cytochrome c oxidase enzyme system in energy production, tyrosine hydroxylase for dopamine receptor synthesis, delta-9 desaturase for myelination, and fatty acid synthesis, and ribonucleotide reductase for brain growth regulation. Also, iron appears to modify developmental processes in hippocampal neurons by altering dendritic growth.
Iodine deficiency is a significant worldwide public health issue, especially in children. There is a relationship between iodine and cognitive development which we usually call as cretinism. It occurs due to a lack of iodine. The clinical manifestation of cretinism depends on the severity of iodine deficiency; the features may include mental retardation, speech and hearing impairment, upper motor neuron, and extrapyramidal lesions.
Iodine is necessary for the production of thyroid hormones in the body.
Iodine deficiency manifests in hypothyroidism, causing the underproduction of thyroid hormones including triiodothyronine (T3) and thyroxin (T4). Thyroid hormones play an important role in neurodevelopment and numerous neurological processes including neuronal cell differentiation, maturation and migration, myelination, neurotransmission, and synaptic plasticity. Iodine further helps in improving fine motor skills and visual problem-solving.
Multivitamin and mineral supplementation:-
Deficiencies of nutrients rarely occur in isolation, and an inadequate diet typically causes multiple micronutrient deficiencies. It is important to investigate the association between multiple minerals and vitamin supplementation or deficiencies and cognitive development. There are multiple micronutrient supplementation in undernourished pregnant mothers resulted in improved motor development, visual attention, and spatial ability in preschoolers.
We can avoid the negative impacts on cognitive developments due to lack of nutrition by maintaining a proper dietary plan.
Dietary pattern and diet quality:-
Since individuals consume combinations of foods. It may contain other bioactive compounds that could act synergistically or antagonistically within or between food groups. Some researchers have investigated the influences of the overall diet on neurocognitive development during childhood. They considered dietary patterns in infancy concerning cognitive development and found higher full-scale IQ at 4 years of age in children who consumed higher amounts of fruit, vegetables, and food prepared at home during infancy.
This association remained significant after adjusting for a wide range of factors, including socioeconomic status, maternal IQ, and education.
These researchers found that a higher level of consumption of fish at 7 years of age and bread and cereals at 3½ years of age was associated with higher IQ scores, whereas those children at the age of 3½ who consumed margarine every day scored significantly lower on IQ. Higher scores on the health-conscious dietary pattern included more salad, rice, pasta, and fruits at 3 years of age. Therefore, the type of breakfast children eat can potentially have a long-term influence on cognitive development. It is observed that carbohydrate-rich, low-glycemic food for breakfast that provides a continuous supply of glucose is known to facilitate better cognitive performance.
The majority of studies have investigated the association between nutrition and cognitive development. They focused on individual micronutrients, including omega-3 fatty acids, vitamin B12, folic acid, zinc, iron, and iodine. The evidence is more consistent from observational studies. It suggests these micronutrients play an important role in the cognitive development of children. However, the results from intervention trials of single nutrients are inconsistent and inconclusive, prompting the need for better controlled and more adequately powered studies in the future.
It is plausible that children living in poor countries may encounter more multiple micronutrient deficiencies.
However, as opposed to children living in rich countries who are reasonably well-nourished and where a small deficiency in one nutrient may not result in measurable, long-term change in cognitive outcomes. This is due to compensation over time.
These are important considerations because nutrients do not act alone, they have in some contexts synergistic and in other contexts antagonistic effects with each other. Individuals consume combinations of food and a poor overall diet can cause multiple macros and micronutrient deficiencies and imbalances.
If an overall healthy diet synergistically enhances cognitive development in children, then public health interventions should focus on the promotion of overall diet quality rather than isolated micronutrients or dietary components consumed by children and adolescents.
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