January 11, 2019
Bottle feeding infants is associated with left-handedness, according to findings of a study conducted at the University of Washington and released on January 7.
The study found that the prevalence of left-handedness is lower among breastfed infants, as compared to bottle-fed babies. This finding was identified in about 60,000 mother-infant pairs and accounted for known risk factors for handedness.
The results provide further insight into the development of complex brain functions which ultimately determine which side of the batter box the infant likely will choose.
“We think breastfeeding optimizes the process the brain undergoes when solidifying handedness,” said Philippe Hujoel, the study’s author, a professor at the UW’s School of Dentistry and an adjunct professor of Epidemiology at the School of Public Health. “That’s important because it provides an independent line of evidence that breastfeeding may need to last six to nine months.”
The study does not imply, however, that breastfeeding leads to right-handedness, Hujoel said. Handedness, whether it be right- or left-handed, is set early in fetal life and is at least partially determined by genetics. The research does sheds light on when the region of the brain that controls handedness localizes to one side of the brain, a process known as brain lateralization. Possibly, the research shows, breastfeeding optimizes this lateralization towards becoming right- or left-handed.
According to Scientific American magazine, about 15% of people are left-handed—and males are more than twice as likely to be left-handed as females. How does that match up with statistics for breastfeeding and bottle feeding? Based on data released by the Centers for Disease Control and Prevention , among U.S. children born between the years 2009 and 2015, 10% were exclusively bottle-fed for the first six months of life; while 30% were bottle-fed exclusively up to the age of three months.
The good news, according to Daily Infographic, is that left-handers are more likely to be geniuses and left-handed men are, on average, 15% more affluent than their right-handed peers.
Interestingly enough, statistically, the older a mother is, the more likely she is to give birth to left-handed children. But we don’t know how likely older mothers are to bottle-feed versus breastfeed.
Research contact: @UWMedicine