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How breast milk promotes newborn brain development

A study reflects the differences between girls who were exclusively breastfed, exclusively bottle-fed, or mixed-fed during their first six months of life

Baby Being Breastfed
Breast milk contains nutritional substances that promote the development and general health of the newborn.Igor Alecsander (Getty Images)
Ignacio Morgado Bernal

Breast milk contains nutritional substances that promote the development and general health of the newborn. But it’s less known whether these substances can affect their brain development and future intelligence. For this reason, a recent study by researchers at Imam Abdulrahman Bin Faisal University in Saudi Arabia attempted to assess whether breastfeeding had affected the general and social intelligence of girls aged between seven and nine. They compared the results of girls who were exclusively breastfed, exclusively bottle-fed, or mixed-fed during their first six months of life.

The results showed that babies fed exclusively with breast milk had a higher body mass index when they reached the age of seven or nine, compared to the other two groups. Likewise, babies who only received breast milk in their first six months of life had higher general and social intelligence quotients than those who were exclusively bottle-fed. While these last results lack statistical significance — bigger studies with a higher number of participants are needed — they open the door to the possibility that breast milk and its ingredients may also specifically contribute to brain development and the future intelligence of newborns.

This summer, a new study from the University of California in San Diego published in the prestigious journal PNAS showed how breast milk could play that role. The key seems to be myo-inositol, a sugar that is very abundant in breast milk and early lactation. Researchers have observed that this sugar intensely promotes the formation of synapses — i.e. the connections between excitatory neurons in the brain. In rat neuron cultures, they observed that the greater the amount of this sugar, the greater the amount of connections between the neurons. In other words, the more myo-inositol, the greater the capacity of neurons to form new synapses. In human brain tissue cultures, this sugar shows equally powerful biological activity, increasing the number and size of postsynaptic specializations and the density of excitatory synapses — a biological revolution capable of promoting the brain development of the newborn.

Ascertaining whether breast milk’s ability to modify brain wiring can be linked to a baby’s future intelligence will require new research, but everything indicates that there is a connection. As we have previously explained, intelligence — as understood as the ability to process cognitive information — lies primarily in the cerebral cortex. Here, humans have 16.3 billion neurons, each of which can in turn relate to several thousand other neurons, i.e. several thousand synapses, thus giving rise to a multiple and intricate network of brain interconnections, which is what differentiates our brain and intelligence from those of other animals such as elephants who, even with a brain much larger than ours, only have 9.1 billion neurons in their cerebral cortex.

Although neuronal interconnections, i.e. synapses, can continue to develop or disappear throughout life, particularly at the end of childhood and the beginning of adolescence, it cannot be ruled out that newborns — who establish a high neuronal connection in the first months of their life thanks to breast milk — start off with greater advantages. In other words, their experience, as shaped by their present and future life conditions, leads them to develop higher analytical and social intelligence skills — as suggested by the study from Saudi Arabia.

In addition to breast milk, myo-inositol — a carbohydrate with a composition similar to glucose — is also present in numerous foods such as black beans, lentils, peas, rice, whole grains, melon, bananas and nuts. Among other functions, it facilitates the effect of the powerful hormone insulin, which can reduce gestational diabetes in pregnant women. Given its presence in such a wide number of foods and the studies that suggest it promotes the development of the newborn’s brain by expanding neuronal connections, it is a good dietary supplement for pediatric nutrition, especially when a mother is unable to breastfeed or is experiencing difficulties.

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