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In the debate over whether babies should be on the breast or bottle, few points may prove as persuasive as the results of a new study indicating that breastfeeding is associated with detectable increases in child cognitive ability and educational achievement.
The study was reported in the January 1998 issue of the journal Pediatrics that is published by the American Academy of Pediatrics. The report is by L. John Horwood and David M. Fergusson from the Christchurch School of Medicine in Christchurch, New Zealand.
The study looked at the relationships between the duration of breast feeding --- how long children were on the breast -- and their cognitive ability and academic achievement over a period of 8-18 years. The data were collected in the course of an 18-year longitudinal study beginning at birth of over 1000 children.
From birth to a year of age, information was collected on maternal breast feeding practices. Then, over the years the children were tested on a range of measures of cognitive and academic performance. These included "measures of child intelligence quotient; teacher ratings of school performance; standardized tests of reading comprehension, mathematics, and scholastic ability; pass rates in school leaving examinations; and leaving school without qualifications."
Longer breastfeeding was found to be associated with consistent and statistically significant increases in:
- Intelligence quotient of the children tested at age 8-9 years
- Reading comprehension tested at age10-13 years
- Mathematical ability tested at age10-13 years
- Scholastic ability tested at age10-13 years
- Teacher ratings of reading and mathematics at 8-12 years and
- Higher levels of attainment in school final examinations.
There were differences between the mothers who breast fed and those who bottle fed. The mothers who chose to breast feed as a group tended to be older, to be better educated and from upper socioeconomic status families. They tended to be in a two-parent family, did not smoke during pregnancy and enjoyed above average income and living standards. The rates of breast feeding also increased with increasing birth weight.
To take these various factors into account, statistical regression adjustments were made for maternal and other factors associated with breast feeding. Nonetheless, the duration of breast feeding remained a significant predictor of later cognitive or educational outcomes.
Breast feeding, it is concluded, is associated with small but detectable increases in the cognitive ability and educational achievement children. These effects are reflected in a range of measures including standardized tests, teacher ratings, and academic outcomes in high school. The beneficial effects of breast feeding in the New Zealand study were long-lived and extended throughout childhood into young adulthood.
The New Zealand study is not alone in suggesting that breast feeding helps children's cognitive abilities and academic achievement. Longitudinal studies have consistently shown that breast fed babies do better in these respects than bottle-fed babies.
What makes the difference? Is it the experience of being on the breast? Or is it the breast milk itself? Data from an experimental study of pre-term (premature) babies show that children whose mothers elect to express their own breast milk later have higher developmental scores and higher intelligence quotients. Thus, the breast milk itself appears beneficial.
What is in breast milk that is so good for the brain? Research has suggested that the helpful factors may be long-chain polyunsaturated fatty acids including, in particular, docosahexaenoic acid (DHA). When DHA was added to infant formulas, pre-term babies appeared to show better visual acuity and cognitive abilities.
The New Zealand investigators observe that their findings "underwrite the need to encourage breast feeding and/or to continue to develop improved infant formulas with properties more similar to those of human milk...." They do believe that their results most likely "reflect the effects of polyunsaturated fatty acid levels and, particularly, DHA levels on early development.
The Nutrition Information Center of New York Hospital-Cornell Medical Center and Memorial Sloan-Kettering Cancer Center recently advised that DHA is "included in infant formulas worldwide, but not in the U.S." (underlined in the advisory). Assuming DHA is required for optimal brain development -- a reasonable conclusion at this time -- the question arises. Why are infant formulas in the United States not supplemented with DHA?