Re Rachael Hamlet's request for citations: In the most well-known of his
papers on this subject, Lucas et al (Lancet 339:261-264, 1992) cite several
studies that related breastfeeding to IQ based on earlier periods when the
correlation was the opposite (wealthier families were the ones that bottle
fed). They mention that one of these studies from 1946 seems to provide
this kind of support--improved IQ in spite of lower SES for the breast-fed
group. I have ordered one of the really old studies (1929) to see what they
came up with.

Lucas et al do a good job of controlling for SES and mother's education but
did not measure mother's IQ, known to be a big factor associated with
baby's IQ (ie genetic). Wright and Deary criticize them for this (Lancet
339:612-613, 1992) but Lucas and Cole do a good job on the second page of
that reference in answering this criticism. Lucas et all were studying
premature babies who received breast or regular (not special premature)
formula by tube. Thus they were measuring an effect of breast milk, not
breastfeeding. This effect might not hold for full term babies, since
prematures might be more sensitive, especially in their ability to
synthesize long chain fatty acids in the presence of inadequate DHA or an
imbalance in fatty acids. Lucas, et al also found that babies of mothers
who wanted to breast feed but could not did no better than the ones who
never intended to breast feed, supporting the hypothesis that it was an
effect of breast milk, not a bias caused by the fact that a different type
of mother wants to breast feed.

Another group found that differences were due to breastfeeding, not breast
milk (Doyle et al, Breastfeeding and intelligence, Lancet 339:744-5, 1992).
Still others (Jacobson and Jacobson, Lancet 339:926, 1992) found that,
while SES and maternal education did not "wipe out" the effects of
breastfeeding, maternal IQ and a measure of parenting skills did.

Later Lucas et al (Arch of Dis in Child 70:F141-F146, 1994) found that
breast milk worked just as well as special preterm formula, even though the
breast milk seemed to be deficient in several nutrients. They write that
this adds "significant support to the view that breast milk promotes
neurodevelopment."
Ted Greiner, PhD
Senior Lecturer in International Nutrition
Uppsala University
75185 Uppsala
Sweden

phone +46 - 18 511598
fax   +46 - 18 515380

e-mail  [log in to unmask]