Researchers at Tufts University's Jean Mayer USDA Human Nutrition Research Centre on Ageing (HNRCA) suggested that micronutrients in human breast milk have considerable positive effects on newborns' growing brains.
The finding provides new information on the connection between nutrition and brain health and could advance infant formulas used in instances where breastfeeding is not an option.
The findings of the study published in the Proceedings of the National Academy of Sciences (PNAS), also pave the way to study what role this micronutrient might play in the brain as we age.
The micronutrient, a sugar molecule known as myo-inositol, was shown to be most prevalent in human breast milk during the early months of lactation, when synapses, or connections between neurons, are rapidly forming in the developing brain.
The researchers profiled and analysed human milk samples gathered across sites in Mexico City, Shanghai, and Cincinnati by the Global Exploration of Human Milk study, which comprised healthy mothers of term singleton infants.
This was true regardless of the mother's ethnicity or origin.
Further testing using rodent models as well as human neurons showed that myo-inositol increased both the size and the number of synaptic connections between neurons in the developing brain, indicating stronger connectivity.
“Forming and refining brain connectivity from birth is guided by genetic and environmental forces as well as by human experiences,” said Thomas Biederer, senior scientist on the Neuroscience and Ageing Team at the HNRCA, senior author on the study, and faculty member at the Yale School of Medicine, where he leads a research group in the Department of Neurology.
Diet is one of the environmental forces that offers many opportunities for study.
In early infancy, the brain may be particularly sensitive to dietary factors because the blood-brain barrier is more permeable, and small molecules are taken in as food can more easily pass from the blood to the brain.
“As a neuroscientist, it’s intriguing to me how profound the effects of micronutrients are on the brain,” said Biederer.
“It’s also amazing how complex and rich human breast milk is, and I now think it is conceivable that its composition is dynamically changing to support different stages of infant brain development.”
Similar levels of myo-inositol across women in very different geographic locations point to its generally important role in human brain development, he observed.
Research by others has shown that brain inositol levels decline over time as infants develop.
In adults, lower than normal brain inositol levels have been found in patients with major depressive disorders and bipolar disease.
Genetic alterations in myo-inositol transporters have been linked to schizophrenia.
In contrast, in people with Down’s syndrome and patients with Alzheimer’s disease and Down’s syndrome, higher than normal accumulations of myo-inositol have been identified.
“The current research does indicate that for circumstances where breastfeeding is not possible, it may be beneficial to increase the levels of myo-inositol in infant formula,” Biederer added.
However, Biederer says it is too soon to recommend that adults consume more myo-inositol, which can be found in significant quantities in certain grains, beans, bran, citrus fruits, and cantaloupe (but which is not present in great quantities in cow’s milk).
“We don’t know why inositol levels are lower in adults with certain psychiatric conditions, or higher in those with certain other diseases,” he said.