Optimizing a Child’s Intellectual Potential
Why nutrients in the first three years of life are mission critical—for smarts and more.
By Hara Estroff Marano published July 5, 2022 - last reviewed on July 5, 2022
Few things in life generate as much joy as the arrival of a newborn infant. Universally, babies excite our deepest dreams and are the bearers of our highest hopes. That is likely because early development is nothing if not the elaboration of possibility. That is especially true of the human brain.
Infants arrive in the world with a full complement of brain cells, about 100 billion neurons. Yet from birth to adulthood, their brains quadruple in size. Most of the growth occurs in the first few years of life: The brain doubles in size the first year and reaches about 90 percent of adult size by age 5.
If the neurons are all there, what accounts for the phenomenal growth? Mostly it is the wiring that connects these neurons, enabling nerve signals to travel from one cell to the next, from synapses to circuits. At birth, the number of synapses per neuron is 2,500, but by age 2 or 3, it’s 15,000 per neuron—the literal embodiment of connective possibility. The explosive growth of synaptic junctures between nerve cells relies on the exponential proliferation of dendrites, the neural tendrils that receive impulses from the outgoing axons of other nerve cells.
Neuron creation begins in week 7 of gestation. Once a neuron is created, it migrates to its place in the brain where it then grows axons and dendrites projecting out from its cell body. While neuron creation is mostly completed at birth, axonal and dendritic projections grow most actively after birth.
In remarkably complex ways still under study, groups of neurons form pathways and circuits to efficiently carry out the brain’s work. The process is heavily based on input from the child’s environment—that is, the child’s early experience. One of the most important sources of input is human interaction. Supportive care and stimulation early in life literally wire the brain, accounting for the degree of dendritic branching, or arborization—provided, of course, that nutrients are also available to build the brain.
The structural and functional foundation established by early care, and especially by the caregiver-infant bond, is one reason why early experiences have an enduring impact on behavior. Early interactions literally pave the paths for future interactions. But so full of possibility is early brain development that synapses are produced with profligacy—and later eliminated if they are not activated. Half of all cells produced in the brain are pruned away throughout childhood and adolescence.
Synaptogenesis is one thing. Another early process underlying later brain capacity is myelination. Myelin is fatty matter that covers axons, serving as insulation that speeds transmission of impulses and gives the brain’s white matter—largely made of nerve projections—its appearance.
Humans are born with a central nervous system virtually unmyelinated; myelination occurs in tandem with development of the brain’s circuitry, most intense in the first few years. Myelination of brain frontal lobes begins at 6 months of age and continues into adolescence. Myelination consistently correlates with the development of childhood cognitive processes and brain processing speed.
In the beginning, breast milk supplies the specific nutritional, hormonal, and other constituents needed for growth, especially brain growth, and the act of breastfeeding sets the stage for social engagement and stimulation. Breast milk is especially rich in nutrients involved in myelin synthesis. But even mothers who breastfeed may become short on some nutrients, as babies’ neural-linked nutrient needs quickly evolve.
The Importance of Vitamins and Fatty Acids
At the very beginning, even before neuron creation, the brain begins as the embryonic neural tube. B vitamins are essential for formation of the neural tube—most notably vitamin B9 (folic acid) and B12 (cobalamin). Severe deficiencies in B nutrition during pregnancy disrupt development of the emerging brain, the reason why grains are now fortified with folate. Deficiencies in early life are also thought to compromise dendrite formation and myelination.
Overall nutrition matters, too, for brain as well as body growth. Inadequate growth leads to smaller brains with less RNA and DNA content, fewer neurons, simpler dendritic trees, and low levels of neurotransmitters and brain growth factors.
Specific nutrients needed for brain growth are long-chain polyunsaturated fatty acids, notably docosahexaenoic acid (DHA) and arachidonic acid (ARA). They promote neuronal growth and white matter development, are structural components of myelin, and abet the maturation of synapses and neural transmission across them.
The frontal lobes of the brain—seat of higher-order cognitive activities as well as emotion regulation—are particularly rich in DHA. Further, DHA is a major constituent of nerve cell membranes and, in that role, facilitates all cell functions. As if that’s not enough, DHA also protects brain tissue from oxidative injury.
Intake of DHA—found in fatty fish—is low among young children. A number of studies show that supplementation improves some facets of cognition and school performance.
The Role of Iron
The mineral iron is another standout among nutrients, and delivery must be carefully timed. It’s essential to the enzyme that regulates division of all cells in the central nervous system and particularly influences growth of the hippocampus, important for learning and memory. Early deficiencies in iron stunt dendrite development, impair myelin synthesis, and limit hippocampus efficiency—deficits that can’t be remedied by later mineral repletion. Synthesis of dopamine and other neurotransmitters also requires adequate iron.
Iron deficiency, however, is the number-one nutritional problem in the world. In the U.S., it is believed to affect 30 percent of children between the ages of 1 and 2. Breast milk contains little iron, and breastfed infants are at risk of iron deficiency after 4 months of age.
Human development unfolds on a schedule that nature has devised. There are critical periods and sensitive periods for growth of major brain structures. A lifetime of cognitive functioning rests on the adequate provision of nutrients at the right time in the first few years of life.
The Brain at Birth
- The brain has its start as the neural tube, which begins forming in the embryo 22 days after conception.
- The neurons of the brain and their supporting glial cells begin proliferating 7 weeks after conception.
- Myelin is produced by the brain’s glial cells.
- Myelination of axons occurs first in areas involved in vision and hearing, then in areas supporting the emergence of language development.
- Linear growth in the first 12 months of life, along with infant birth weight before 4 months of age, significantly predicts children’s I.Q. at 9 years of age.
- Intense as it is in the first few years, synapse formation between axons and dendrites actually continues throughout the lifespan.
- Synapse formation is the major mechanism of brain plasticity, allowing the brain to organize and reorganize itself in response to the environment at any age.