Brain development

Brain development starts in utero, and while the cognitive, social and emotional parts of the brain will continue to development across the lifespan, a great deal of the brain’s ultimate structure and capacity is shaped early in life before 3 years of age [1].

From birth to 6 months of age, the brains prefrontal cortex has a growth spurt. This area of the brain is involved in complex processing behaviours, attention and multitasking. The hippocampus is also growing at a rapid rate, developing baby’s recognition and memory.

Myelination is a process that helps the brain develop the flexibility needed for electrical impulses involved in neurotransmission. This process accelerates around 32 weeks gestation and continues during the first 2 years of life.

DHA from omega-3 fatty acids is a critical nutrient needed for myelination and healthy neurosignaling, and while breastmilk contains DHA, levels are dependent on mother’s dietary intake. Western countries such as Australia, USA and the UK have shown lower levels of breastmilk DHA compared to countries with high fish consumption such as Japan [2].

Key nutrients for brain development

Nutrient	Function	Dietary Sources
DHA	Brain development and function: structural component of grey matter, development and function of myelin.	Breastmilk or Infant Formula
ARA	Developing brain and nerve pathways.
Choline	Needed for cell division & growth particularly in the foetal brain & continuing until 3-5 years of age. Provides structural integrity of membranes and neurotransmission [3].
Iron	Brain development, neurotransmitter production & red blood cells.
Folate	Brain development, neurotransmitter production & cell division.
Zinc	Brain development, neurotransmitter production & myelination. Behaviourally, early life zinc deficiency results in poorer learning, attention, memory and mood [4].
Vitamin D	Deficiency may cause behavioural, memory, and learning disorders later in life [5].
Vitamin B12	Brain development & nervous system function.

Eye development

A baby is not born with perfect vision, in fact it takes a few months for baby’s eyes and vision to properly develop. Newborn babies primarily focus on objects 8 to 10 inches from their face, roughly the distance to the parent’s face.

By 2 months of age, babies can focus their eyes better on the object or person in front of them, and by 3 months they can follow and reach for objects. As baby’s brain is making new connections and the eyes and vision are improving, baby will start noticing his own hands, turn his head towards a sound and reach for and hold toys [6].

The ability for babies to see colour develops over the first 6 months of life. When babies are born, they can only see shades of colour, but by about 5 months babies generally have good colour vision [7].

Key nutrients needed for eye development

Nutrient	Function	Dietary Sources
Vitamin A	Required for vision and retina development. Infants accumulate stores in the 3rd trimester of pregnancy and rely on breast milk for continued supply until the introduction of solid foods [8].	Breastmilk or Infant Formula
Lutein	A carotenoid that accumulates in the retina where it prevents damage from reactive oxygen species.
DHA	Needed for the growth and development of the brain and retina, where it accumulates [9].

Bone and teeth development

Babies are born with 20 baby teeth (also known as primary teeth) which stay under the gums until about 6 months of age when baby’s first teeth begin to appear. Teeth can start moving under the gums causing teething symptoms as early as 2 months of age.[10].

Babies are born with soft, flexible bones, and spaces between the bones on the skull, known as fontanelles (soft spots) which help delivery through the birth canal. The newborn skeleton contains a lot of cartilage, which begins to harden into bone at around 3 months of age.

Sufficient vitamin D stores passed on from the mother during gestation are critical for bone development. Preterm babies and babies born to mothers with vitamin D deficiency are usually given infant vitamin D drops to prevent Rickets and support normal bone development.

Key nutrients needed for bone and tooth development

Nutrient	Function	Dietary Sources
Calcium	Mineralization and growth of bones and teeth as cartilage is replaced with solid bone	Breastmilk or Infant Formula
Vitamin D	Needed for normal bone formation, absorption of calcium from the diet, and prevention of Rickets.	Breastmilk, Infant Formula or infant supplement
Vitamin K	Absorption of calcium within bone during development and elongation.	Administered at birth. Breastmilk or Infant Formula
Phosphorus	Maintain bone mineralisation	Breastmilk or Infant Formula
Manganese	Bone formation	Breastmilk or Infant Formula

Intestinal, gut microbiota and immune development

While scientists have always believed that babies are born with a sterile gut [11], this topic is being debated [12]. Whether or not the infant gut is sterile, babies are born with a very limited microbiome, which begins to develop rapidly after birth.

Babies born vaginally acquire bacteria passed on through the birth canal which begins colonization of the infant microbiome. Colostrum and early breastmilk contain high levels of beneficial bacteria, prebiotic sugars and immune stimulating compounds deigned to begin the microbiome and immune system development.

Newborns have a permeable gut, sometimes referred to as an ‘open gut’. The gaps in between the cells of the intestine allow for the transfer of immunoglobulins passed on from breastmilk to stimulate early immune system development. Intestinal permeability gradually decreases over the first 2 months of life and is complete by the time solids are introduced (not before 4 months of age) [13].

Key nutrients needed for digestive and immune development

Nutrient	Function	Dietary Sources
Vitamin A	Formation and maintenance of mucous membranes (intestines), immune system development and function.	Breastmilk or Infant Formula
Zinc	Formation and maintenance of mucous membranes (intestines), immune system development and function.
Vitamin C	Formation of collagen and connective tissue, immune system development and function.
EPA & DHA	Immune system development and function.
Galacto-oligosaccharides (GOS), Human milk oligosaccharides (HMO)	Prebiotics – help to feed beneficial bacteria that colonize and reside in the gut.
Lactoferrin	Stimulates the immune system, promotes growth of gut microbes; antibiotic properties.
Nucleotides	Immune system development, growth, development and repair of the gut.

Developmental milestones birth to 6 months:

Gross motor skills: lift head, straighten legs on flat surface, roll on tummy, sit briefly unsupported.

Fine motor skills: hold object, reach for dangling objects, notice own hands and play with fingers, pass toy from one hand to another.

Self-help skills: open mouth when see breast or bottle, bring toy to mouth, place both hands on breast or bottle during feeds.

Cognitive skills: looks at people’s faces, eyes follow moving object, focus eyes on sound, find toy partially hidden under cloth [6].

References

Fox SE, et al. Child Development. 2010; 81:28–40.
Mosca F, et al. Pediatr Med Chir. 2017; Jun 28;39(2).
Derbyshire E, Obeid R. Nutrients. 2020 Jun 10;12(6):1731.
Cusick SE, Georgieff MK. The Journal of Pediatrics. 2016 Aug;175:16-21.
Cerdó T, at al.Curr Opin Clin Nutr Metab Care. 2019 Nov;22(6):434-441.
http://www.childrensmn.org/references/pfs/rehabpublic/developmental-milestones-birth-6-months.pdf
https://www.aoa.org/healthy-eyes/eye-health-for-life/infant-vision?sso=y
https://www.rch.org.au/immigranthealth/clinical/Vitamin_A/
Huang HL, et al. Lipids Health Dis. 2013 Mar;12:27.
Http://www.pregnancybirthbaby.org.au/how-your-babys-teeth-develop
Khan S, et al Archives of Disease in Childhood. 2015;100:A50-A51.
Willis KA, et al. FASEB J. 2019 Nov;33(11):12825-12837.
Castellaneta, et al. Journal Pediatric Gastro Nutr: 2005 May;40(5):632.