The study drew on the success and failures of 1,414 U.K. babies born in the 1920s and 1930s, a population now in their seventies. The study, to be published soon in the Archives of Diseases of Childhood, suggests that the children who were breast-fed were 41 percent more likely to rise up at least one level in the social ladder compared to others who were fed cow's milk, the only alternative at the time.
A study in the Lancet, a British medical journal, suggests that breastfeeding raises a preterm babies' IQ by up to 5 points, and other studies have correlated breastfeeding with higher intelligence, but the findings contradict other research: a study from the Medical Research Council published in 2006 indicate breast-fed babies had a higher level of intelligence not from the milk but from other factors like a more active and stimulating home environment.
"One of the most consistent findings in the published literature on the long-term impact of infant-feeding is that breastfeeding is associated with improved neurocognitive development, which could influence future educational and occupational success and hence social mobility" the researchers wrote in the study.
Consumer health advocate Mike Adams said that the natural nutrients found in breastfeeding make it an optimal choice.
"Although few people will say the obvious, what's really happening here is that cow's milk impairs the intelligence of babies," Adams, author of the book Grocery Warning, said. "Human breastmilk contains the nutrition to build healthy, peak-performance nervous systems and cognitive function in human beings, and milk intended for cows simply lacks that nutrition."
"Mothers who feed their infants cow's milk are, in effect, making it more difficult for their children to succeed in life," he added.
The lead researcher of the University of Bristol study, epidemiologist Richard Martin, said one caveat is that while breast-fed babies moved up the social ladder more than their bottle-fed counterparts, both groups were capable of doing so: half of the bottle-fed babies moved up the social ladder, but nearly 6 out of 10 of breast-fed babies did the same thing.
Among British women, 76 percent do breastfeed when a baby is born, but most wean their children to bottles within the first four months.