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Breast-Feeding
Linked to IQ Gain
Supporting
the conclusion that breast-feeding improved intelligence, researchers found a
strong "dose effect" -- a gradual improvement based on the number of
months of breast-feeding up to nine months, when the effect ended. Results
from the study, of more than 3,000 young men and women from Copenhagen, Denmark,
strongly support the long suggested, but unproved, conclusion that
breast-feeding makes babies not only healthier, but smarter. As
the first study to measure the effects of breast-feeding into the subjects' late
teens and twenties, it could become an authoritative statement in the emotional
debate over how to encourage nursing. Today, the practice is most common among
white and wealthier women and least common among minority and poorer women. "We
are really quite certain that what we are seeing here is the effect of the
duration of breast-feeding on an individual's intelligence," said June
Machover Reinisch of the Kinsey Institute for Research in Sex, Gender and
Reproduction, one of the study's authors. "The question that remains is
what exactly is the aspect of breast-feeding that results in the greater
intelligence." "The
evidence is growing that breast-feeding is among the most important lifelong
benefits a mother can give to her child," she said. Although
public health officials, and even infant formula producers, recommend
breast-feeding as the best way to nourish an infant for the first six to 12
months, most American babies are bottle-fed during much of their infancy. The
proportion of mothers who begin breast-feeding has been increasing in recent
years to almost 70 percent, but a study by the infant formula industry found
that only 31 percent of all infants are still being breast-fed at 6 months.
Because of previously studied health effects, the American Academy of Pediatrics
recommends one year of breast-feeding as optimal. Studies
have shown that many women never breast-feed or stop quickly because of a wide
range of ambivalent or negative signals from society. Researchers have
identified cultural biases against the practice, serious difficulties
experienced by some mothers when they return to work, limited availability of
training in how to breast-feed, and the sometimes aggressive advertising and
promotion of the infant formula industry. About half of all the formula used in
the United States is purchased for poor women through the federal Women, Infants
and Children program (WIC). The
JAMA findings could also have an impact on the infant formula industry. A new
type of formula, supplemented with two beneficial compounds found in breast milk
but not in traditional formula, has recently come onto the market. Makers of the
new formula believe their studies have shown the added ingredients could be
responsible for some of the benefits of breast milk on intelligence, although
the Food and Drug Administration did not evaluate that issue when it approved
the formula. While
some previous studies have suggested an association between breast-feeding and
improved intelligence, the new study appears to provide the strongest indication
of an effect. The
research, funded primarily by the National Institutes of Health, used two large
groups of Danish men and women who had been studied since their mothers were
pregnant with them between 1959 and 1961. When the children were one year old,
the mothers were questioned about how long they breast-fed their babies. One
group of 973 men and women was given a Wechsler Adult Intelligence Scale test,
an intensive one-on-one assessment, while the other sample of 2,280 men received
intelligence tests when they entered the Danish military. Testing of both groups
occurred in the 1970s and 1980s. In a recent analysis of the data for the JAMA
study, researchers found that in both groups, those breast-fed nine months
scored significantly higher than those breast-fed for less than one month. Other
studies have shown a correlation between breast-feeding and scores on
intelligence tests, but some of that relationship disappeared when complicating
factors were taken into account. For instance, the children of mothers who are
better educated and wealthier would be expected to be healthier and to score
higher on intelligence tests however they were fed as infants. Their mothers
would be statistically less likely to smoke, to be overweight and to have large
families -- all associated with less healthy children who do less well on
intelligence tests. But
the new Danish study took into account 13 similar factors related to the
mother's health, wealth and behavior when analyzing the difference between the
scores of more breast-fed and less breast-fed young adults. The differences held
up after they were factored in. Some
experts yesterday cited one possible weakness in the study, in its reliance on
the mothers' recollections of how long they had breast-fed their children. Those
recollections, these experts said, may not be entirely accurate. Researchers
said the results were potentially more meaningful than earlier studies that
looked at intelligence in young children, which is less stable and more
difficult to measure with confidence. Nonetheless,
some of the earlier studies also showed significant results. A recent study, led
by Malla Rao of the National Institute of Child Health and Human Development,
found that babies born small but at term and breast-fed for six months scored an
average of 11 points higher on intelligence tests than those breast-fed for 3
months. The IQ tests were given when the children were 5. The
JAMA report offers three possible explanations for the association between
breast-feeding and higher scores. The first is that two fatty acids associated
with the development of nerve cells and the brain are present in breast milk but
absent from infant formula and cow's milk. The two, docosahexaenoic acid (DHA)
and arachidonic acid (ARA), have been shown in some experiments to improve
eyesight and some motor responses in infants and young children. According
to author Reinisch, these two compounds are among hundreds found in breast milk
but not in substitutes. Other substances found in breast milk have been shown to
improve a child's respiratory and gastrointestinal health as well. The
authors also suggest that the mother-infant bond can be deepened through
breast-feeding, and that that contact may affect the child's intellectual
development. They report as well the hypothesis that how long a mother
breast-feeds is an "indicator of the interest, time and energy that the
mother is able to invest in the child during the whole upbringing period."
© 2002
The Washington Post Company |