Breastfeeding during early childhood is associated with positive life outcomes, ranging from improved metabolic health to greater cognitive ability. Researchers believe this effect stems from human breast milk being particularly rich in indigestible sugars, many of which are exclusive to the human species and known as human milk oligosaccharides (HMOs). Now, a new study reports that a particular class of HMOs may be uniquely crucial – at least when it comes to cognitive development.

The researchers conducted their study in piglets, whose anatomical and cognitive development resembles that of human children. Starting at two weeks of age, piglets were randomly selected to receive one of four milk replacement formulas: a control formula mimicking the oligosaccharide composition of pig milk, and three others containing various types of HMOs.

Eight weeks later, piglets were transitioned to a solid diet and trained on a challenging memory task that required them to remember which four out of 16 possible locations in a large arena contained hidden food rewards. For an extra challenge, they started each new trial from a different drop-off point, which meant that they had to actively engage with their surroundings to navigate to the rewarded spots.

Then the animals completed a test of cognitive flexibility – the ability to adapt to changing environments and rules. The researchers baited a new set of four locations with the food rewards and watched how quickly piglets reacted to the change. They found that the piglets that had consumed formula containing sialylated HMOs (HMOs containing a special sugar called sialic acid) were better learners than their peers, especially those whose formula mimicked pig milk. This last group were slowest to learn the new reward locations and more likely to accidentally re-visit spots where they had already collected a reward – a sign of short-term memory lapse.

These results suggest that sialylated HMOs are a particularly crucial component of breast milk for the development of flexible cognition. This effect might be underpinned by the oligosaccharides' high content of sialic acid, which is found in brain cell membranes and implicated in regulating cellular communication, developmental gene activity, and myelination, (the process of coating neuronal axons in fatty tissue that speeds up signaling). Learn more about HMOs and other beneficial components of breast milk in this episode featuring Dr. Rhonda Patrick.

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