Whether you bottle feed or breastfeed your child could play a role in what hand they prefer to use later in life, according to a new survey from the University of Washington. In a review of more than 60,000 mothers and their newborns, the researchers determined that bottle feeding babies was associated with a higher prevalence of them being left-handed even when accounting for known risk factors that may influence which hand a child favors.
To determine how feeding an infant may influence their dominant hand, researchers gleaned data on the duration of breastfeeding as reported by the mother through seven national surveys in five countries. They found that breastfeeding for more than six months was associated with 3 percent less left-handed babies than those that were bottle-fed, with about one in five left-handed bottle-fed babies perhaps being attributable to a lack of breastfeeding for more than six months.
“We belief breastfeeding optimizes the process the brain undergoes when solidifying handedness, ” said investigate writer Philippe Hujoel in a statement. “That’s important because it renders an independent line of evidence that breastfeeding may need to last six to nine months.”
Writing in the journal Laterality: Asymmetries of Body, Brain and Cognition , the scientists say their study sheds light on when areas of the brain, such as those that control handedness, localize to one side in a process known as brain lateralization. Breastfeeding, they write, may optimize this lateralization toward becoming right- or left-handed during a critical window of hour during the first nine months of infancy.
“[ Our] current findings thus suggest that the critical period of cerebral lateralization, the time window wherein brain lateralization is susceptible to fostering, starts sometime before the 3rd month in utero. The developmental origins of laterality and ends in infancy before the age of 9 months, ” said Hujoel.
According to the paper, previous learns have found that “breastfed babies have been reported to have increased righthandedness, increased intelligence, increased brain circumference, decreased speech troubles, and lessened multiple sclerosis, ” while other studies have interpreted these associations as causal based on evidence that breastfeeding leads to more grey matter volume in the brain. However, these studies don’t always accurately account for socio-economic factors and health awareness( among other factors) due to the difficulty in parsing out baffling factors.
The study does not indicate that breastfeeding alone dictates what hand small children will favor later in life, as this is determined during fetal life and at least partly by genetics. Further, it’s important to note that although they used a random sample to reduce selection bias, use trained examiners to reduce datum bias, and that public availability of the data allowed for independent verification of reporting biases, the researchers had pointed out that farther, broader research is needed.