Breastfeeding and intelligence

Breastfeeding makes babies brainier is hitting the news wires again to no surprise to those working in breastfeeding and child development. Summaries of key research on this topic follow:

Breastfeeding and later cognitive development and academic outcomes
Horwood, L.J. and Ferguson, D.M. Abstract. Pediatrics, 101(1) 99. 1998 (electronic abstracts http://www.pediatrics.org/cgi/content/full/101/1/e9)

This New Zealand longitudinal study examines the association between the duration of breastfeeding, childhood cognitive ability and academic achievement from the ages of 8 to 18 years. Data was collected on breastfeeding practices from birth to 1 year and between 8 and 18 years on such things as IQ, teacher ratings of school performance, reading comprehension and math tests, and pass rates in school exams.

Results demonstrated increased duration of breastfeeding was associated with statistically significant increases in IQ assessed at the ages of 8 and 9; reading comprehension and math ability assessed at ages 10 to 13; teacher ratings of math and reading assessed at ages 8 and 12; and higher levels attained in school leaving exams.

The authors concluded that breastfeeding is associated with a small but detectable increase in child cognitive ability and educational achievement and that these effects are broad and extend into childhood and early adulthood.

Influence of breast-feeding on the infant’s intellectual development
Temboury, M.C. et al. J. Pediatr Gastroenter Nutr 18:32-36, 1994

To determine the effects of breastfeeding on the intellectual development of infants, this prospective Spanish study of 229 infants from birth to 2 years were tested using Bayley’s Scales. After controlling for confounding factors, the bottle fed group (99 infants) had lower results on the Bayley’s tests for mental development and also for motor development. The latter was only associated with lower and lower-middle social status. The study concluded that breastfeeding acts as “protective mechanisms for the mother and child in an adverse environment” and that breastfeeding itself “improves the mother-child relationship and the infant’s stimulation.”

Neurological differences between 9 year-old children fed breast-milk or formula as babies.
Lanting, C.I. et al. Lancet. 344:1319-1322, 1994

The effect of breastfeeding on the neurological development of children at age 9 is the focus of this Dutch retrospective study. A total of 135 breastfed and 391 formula fed infants, after adjustment for obstetric, perinatal, neonatal, neurological and social differences were given a follow-up neurological examination at 9 years of age.

Children fed with artificial milks exclusively or supplemented to breastmilk within the first three weeks of life were found to have twice the rate of minor neurological dysfunction as compared to children fully breastfed at least for the first 21 days of life. The authors suggest that the presence and severity of minor neurological dysfunction is related to behavioural and cognitive development at school age. Three possible mechanisms for the differences are suggested. First, the psychosocial features of breastfeeding. Second, maternal hormones, such as the thyroid stimulating hormones secreted through breastmilk may have an impact. Third, the beneficial effects of essential long chain fatty acids (arachidonic, docosahexaenoic) known to be present in breastmilk and missing in most artificial baby milks.

Breast milk and subsequent intelligence quotient in children born premature.
Lucas, A. et al. Lancet 339:261-264, 1992

This very interesting British follow-up study of premature infants reports the intelligence quotients results of 8 year olds who had been fed their own mother’s milk after birth. The children who had received their mother’s milk had a significantly higher IQ at ages 7.5 to 8 years than children who did not receive breastmilk. After adjusting for differences between the two groups, the study children had an 8.3 point advantage in IQ scores. Interestingly, this difference was not attributed to the interaction between the mother and infant because the infants had been fed by nasogastric tube.

Also the researchers were able to show a dose relationship between the amount of breastmilk fed and the subsequent IQ outcomes. They concluded that breastmilk itself conferred substantial advantages for cognitive development and that this could perhaps be explained by the presence of various factors in breastmilk necessary for the development of neural tissue such as long chain fatty acids which are completely missing in infant formulas. (DHA is uniquely high in the mother’s milk of a premature infant.)