left-handed

A recent study explored breastfeeding in comparison to bottle-feeding. Specifically, researchers looked into breastfeeding duration and its impacts on infants becoming right or left-handed.

Breastfeeding and bottle-feeding concerning infants’ neurodevelopment continues to be a strong conversation. Infants’ intelligence levels, speech, and head circumference are often analysed in association with breastfeeding and bottle-feeding. Does the length of time a mother breastfeeds influence whether or not her infant will become right or left-handed?

A study published in Laterality: Asymmetries of Body, Brain and Cognition explored and obtained results from previous surveys about breastfeeding. A total of seven surveys were assessed for risk of bias, participant data, and IPD meta-analysis. Around 60,000 mother-infant duos were examined from previous studies and surveys.

The study suggests that bottle-feeding may be correlated with left-handedness. The findings showed that when compared to bottle feeding, breastfeeding for less than one month presented a 9% decreased prevalence in left-handedness. One to six months of breastfeeding showed a 15% decrease, while more than six months showed a 22% decrease. Breastfeeding for more than nine months did not reveal any further decreases.

It is important to note that these findings do not indicate that breastfeeding results in right-handedness. However, they do suggest that breastfeeding duration may have a strong impact on an infant’s brain lateralization, especially within the first nine months of life.

The authors note that handedness may or may not be related to nutrition. What may be more strongly associated is the sense of nurture that is associated with mother-infant bonding. Therefore, handedness may be strongly connected to the amount of nurture an infant receives. However, it is important to keep in mind that handedness is somewhat influenced by genetics.

Larger randomized studies (approximately 1 million women) are suggested for further understanding of breastfeeding and bottle-feeding and their possible associations with right or left-handedness.

Written by Laura Laroche, HBASc, Medical Writer

References:

  1. Hujoel, Philippe P. “Breastfeeding and Handedness: A Systematic Review and Meta-Analysis of Individual Participants Data.” Laterality: Asymmetries of Body, Brain and Cognition. 2019. 1-19. Online.
  2. Long-term breastfeeding sheds light on whether an infant becomes right- or left-handed. 2019, https://www.eurekalert.org/pub_releases/2019-01/uow-lbs010719.php, assessed 17 Jan. 2019.
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