(RxWiki News) You may have heard that "breast is best" when it comes to feeding a baby. The benefits of breastfeeding are significant, but it has not always been clear how they extend to a baby's brain development.
Now, a recent study found that being breastfed longer was linked to higher IQ scores for kids at ages 3 and 7.
The increases in the scores were relatively small, but they did not appear to be explained by other factors that the researchers considered.
Babies who were exclusively breastfed saw higher scores than those who had never been breastfed or partially breastfed.
"Ask your OB/Gyn about how long you should breastfeed."
This study, led by Mandy B. Belfort, MD, MPH, of Boston Children's Hospital and Harvard Medical School, dug deeper into the effects of breastfeeding on a child's brain development, including the diet of the mother.
In analyzing the breastfeeding mothers' diets, the researchers focused on any possible effects on the children whose mothers ate two or more servings of fish each week.
The researchers tracked 1,224 children from before they were born (while their mothers were pregnant) through age 3. Of these, they tracked 1,037 through age 7.
The researchers gathered data from the mothers on how long the children had been exclusively breastfed through age 1.
Overall, the children had been breastfed for an average of 6.4 months, including an average 2.4 months of exclusive breastfeeding.
The children underwent several assessments at 3 and 7 years old to measure their language abilities and intelligence.
The children underwent a Peabody Picture Vocabulary Test at age 3, an assessment of their motor skills at age 3 and 7, a memory and learning test at age 7 and an IQ test at age 7.
Then the researchers analyzed the test results along with how long the children had been breastfed, taking into account the mother's IQ and the family's income, social background and home environment.
The researchers also took into account the child's age, sex, race/ethnicity, growth while in the womb and the week of pregnancy when the child was born.
Further, the researchers also looked at the mother's age, the number of children she had, her educational level, her marital status, whether she smoked, whether she was employed, what kind of child care her child received at 6 months old and whether she had had depression.
The researchers found that children who had been breastfed longer had higher scores on the picture vocabulary test at age 3.
For every additional month the child was breastfed at all, their score on this test was 0.21 points higher. For every additional month the child was exclusively breastfed (no formula or other foods except breastmilk or water) through 6 months old, the score was 0.5 points higher.
This test is scored like an IQ test, with 100 being the average. A score of 115 is one statistical notch above average, and 85 is a notch below; about two-thirds of all people will have an IQ score between 85 and 115.
The difference was more significant when comparing children who had only been breastfed with those who had never breastfed.
"Compared with children fed breast milk only, the Peabody Picture Vocabulary Test score at age 3 years was approximately three points lower for children never breastfed and approximately two points lower for weaned children and those receiving mixed feedings [before 6 months old]," the authors wrote.
Similarly, children who had been breastfed longer scored higher on the IQ test when they were 7 years old.
For every additional month a child had been breastfed before age 1, the child scored an average 0.35 verbal points higher and an average 0.29 nonverbal points higher on the IQ test.
Among children exclusively breastfed through 6 months old, each additional month of breastfeeding translated to an average 0.8 verbal points higher and an average 0.58 nonverbal points higher.
Again, the researchers compared children who had never been breastfed with those who had ever been breastfed (regardless of how long or whether they also had formula), taking into account the other factors that might influence children's scores.
"Compared with children who were never breastfed, the fully adjusted Peabody Picture Vocabulary Test score at age 3 years was [an average] 1.45 points higher for children who were ever breastfed, and the [IQ] verbal score at age 7 years was [an average] 3.75 points higher," the researchers wrote.
However, the researchers did not find any differences among the children on the memory and learning test the children took at age 7, regardless of how long they had or hadn't been breastfed.
No differences were observed among children, regardless of how long they were breastfed, for the motor skills tests except among 3-year-olds whose mothers had eaten at least two servings of fish each week while breastfeeding.
On the motor skills test at age 3, children of moms who ate two fish servings a week had average scores about 0.24 points higher for each additional month they were breastfed.
This study was published July 29 in JAMA Pediatrics.
The research was funded by the National Institutes of Health. The authors declared no conflicts of interest.