Does breastfeeding make your child smarter?

by Rhona Mahony

Mothers can make breastmilk, but fathers can't. Does that difference impose a limit on how much responsibility for baby care fathers can take, or should take? Whether it does depends how beneficial breastmilk is for babies and whether fathers can deliv er it.

As most readers know, special pumps, baby bottles, and refrigeration make it possible for mothers in developed countries to express their milk and store it safely. In several nontraditional families I interviewed in 1993, the mother worked for pay full- time to support her family while the father stayed home to take care of their baby. The mother pumped milk several times during the day at her office, stored the bottles in a refrigerator, and brought them home in the evening. The father fed the milk to the baby the next day. One father called the bottles "TV dinners." The parents went to this extra trouble because they strongly believed that breastmilk conferred benefits on their baby that formula couldn't provide. Modern technology, then, makes it possible for a father who is the primary parent to nourish his baby exclusively with breastmilk.

Still, pumping isn't for everyone. Mothers living in poor countries or under unhygienic conditions may not have the clean equipment and reliable refrigeration necessary. Mothers who travel on business, who work under rough physical conditions (such as park rangers), who have no privacy at work, or who have no refrigerator at work (anyone who drives a car or truck all day) will find pumping very inconvenient. Moreover, some women find it hard to get milk into one of those darned plastic bottles even un der the best of circumstances. Milk comes out after the mysterious "let down" reflex occurs. A woman's emotional state and physical environment can help or hinder the let down. In my case, for example, with my baby in my arms, let downs came magically, every time. Away from my baby, fumbling with the plastic pump and the sheet of instructions, it never happened. A different sort of pump, the right music, or weeks of persistence may have paid off. The things was, I didn't have weeks, and it was defin itely frustrating. So, after my husband and I talked it, we decided that for the several feedings a day I'd be away from home at work, our baby would get bottles of formula.

Thus, pumping has costs: time, effort, and inconvenience. For some mothers who are primary or major breadwinners for their families, those costs will be substantial.

That brings us to the next question: how valuable is giving breastmilk to babies? Researchers in pediatrics agree on a wide range of benefits that breastfeeding, and breastmilk in particular, confer on babies.(1) Benefits include the delivery to bacter ial and viral antibodies to the baby, stimulation of the growth of friendly bacteria in the baby's intestines, and fewer allergic reactions in breastfed babies. Recently, some researchers have reported more dramatic benefits: a lower incidence of neurol ogical problems in breastfed babies and even a significant boost in IQ scores.

Aaah! Now the stakes are higher. In the rich countries, mothers who choose to breastfeed are disproportionately well-educated, middle class, and eager to promote their babies' development. Who wants to rob their baby of precious IQ points?

Alan Lucas, of Cambridge University's Department of Pediatrics, led the team that found the IQ effect.(2) His project was part of a larger research effort studying the effect of different sorts of diets on the growth and development of premature babies (under 1850 grams, or 4.08 pounds, at birth). In parallel studies, these tiny infants were fed a special new formula for preemies, donor's breastmilk, or their mother's breastmilk.(3)(4) Once the babies reached 2000 grams (4.4 pounds), they were sent ho me. The babies' median hospital stay was four weeks. Doctors followed the children after they were sent home so that months and years later they could give them tests of their physical, cognitive, and social development.

Surprisingly, tests given to 300 of the children when they were seven and a half to eight years old found that those who had been fed their mother's breastmilk as newborns had a significantly higher IQ score than those who had gotten no breastmilk. The hospital staff fed all the preemies through a tube, so if there was an IQ effect, it was caused by the breastmilk itself, not the act of breastfeeding.

Of course, there were big socioeconomic differences between the mothers who chose to give breastmilk to their babies and those who didn't. Everyone knows that children's IQ scores correlate with the socioeconomic level of their parents, so the researche rs controlled statistically for the parents' occupations, the mother's educational attainment, and the birth order of the child (e.g., was it the first, second, or third baby surviving in the family). Even after adjusting for those differences, though, t he researchers found that the breastmilk-fed children had an 8.3 point advantage (over half a standard deviation) in IQ. Interestingly, the children of well-off, highly educated mothers who chose to give breastmilk but, to their surprise, weren't able to had scores similar to the no-breastmilk babies, and lower than the breastmilk-fed children of well-off, highly educated mothers.

What do those dramatic results mean? No one knows for sure. Lucas's team thinks that breastmilk may contain ingredients that especially promote brain development in premature infants. Scientists know that long-chain lipids are important in brain devel opment, and that baby formulas don't contain them. Other hormones and growth-promoting ingredients present in breastmilk could be responsible. Still, something else might cause the advantage in IQ that Lucas's team found. For example, mothers who chose to give breastmilk and were able to might, on average, have had better parenting skills than the other mothers or some genetic advantages.

A Dutch team, led by C. I. Lanting, also found neurological advantages in children who were fed breastmilk.(5) They gave neurological tests to over 600 nine-year-olds who had been born full-term. They controlled statistically for the mothers' education al attainment and birth order, but not for the parents' occupations. They found that the breastfed children had a lower incidence of neurological abnormalities than non-breastfed children. The breastfed children had been breastfed for a median of seven weeks. An intermediate group of children got a combination of breastfeeding and formula. The researchers found little difference between the exclusively breastfed children and the children in the intermediate group. Note that this study did not use tub e-feeding, but old-fashioned nursing at the breast.

The Dutch project is even harder to evaluate than Lucas's British study, in part because the researchers didn't take into account many socioeconomic factors that we know correlate with children's health and cognitive abilities. Also, nursing at the brea st may be beneficial for babies in ways that we don't understand. Also, willingness and ability to breastfeed may correlate with other things--attitudes, skills, or family styles--that correlate with good neurological development. Still, the Dutch team may have found that breastmilk--exclusively or in combination with formula--confers a small benefit on full-term babies.

What should we make of this research? Notice a couple of things. First, the most dramatic results were found in a very special group of babies--preemies under 1850 grams. It's possible that most babies, who are born full-term and therefore are much f urther along in their brain development, won't show the same effect. Second, babies in both the British and Dutch studies were fed breastmilk for only a short while: a median of four weeks and seven weeks respectively. Most women who work for pay take a maternity leave of four weeks or more. Those who are willing to breastfeed or express breastmilk will, then, be home to do it for the early weeks covered in these studies without compromising their job performance. Third, the Dutch study found that bab ies fed both formula and breastmilk during their earliest weeks seemed to show the same neurological advantages as babies who were exclusively breastfed.

I conclude that these findings suggest that mothers who work at demanding jobs to support their families and fathers who do many, most, or all of the baby's feedings can take superlative care of their infants. Many nontraditional couples might consider the following plans: Mom breastfeeds for half or more of the feedings during her maternity leave. Dad (or another caretaker) bottlefeeds--with breastmilk or formula--for half or fewer of the feedings during that time. After Mom returns to work, she can breastfeed once in the morning and once or twice night and Dad can do the other feedings, with formula or expressed breastmilk. Or, once Mom returns to work (between weeks three and eight), she stops providing breastmilk, if the demands of her job (for example, overnight trips away from home), make it impossible for her to maintain her milk supply comfortably. Even if the British and Dutch findings are correct, a baby on any of these plans would get the special benefits of breastmilk that they report.< p> What about mothers and fathers who don't want to provide breastmilk, or can't? They should note that the findings of both studies are still being debated by pediatric researchers. Unaccounted for social or genetic factors, or other things, could be res ponsible for the findings.

In short, the "anatomy is destiny" crowd has lost another round. Dads can't make breastmilk, but it doesn't seem to matter one bit.

(1) See, for example, Richard E. Behrman, Victor C. Vaughn, and Waldo F. Nelson, Nelson Textbook of Pediatrics, Thirteenth Edition (W.B. Saunders Co., Philadelphia, 1987), p. 124-125.
(2) A. Lucas, et al., "Breast milk and subsequent intelligence quotient in childen born preterm," The Lancet, vol. 339, pp. 261-264.
(3) A. Lucas, et al., "Early diet in preterm babies and developmental status at 18 months," The Lancet, vol. 335, pp. 1477-1481.
(4) A. Lucas, et al., "Multicentre trial onfeeding low birthweight infants: effects of diet onearly grwoth," Archives of Disease in Childhood, vol. 59, pp. 722-730.
(5) C.I. Lanting, "Neurological differences between 9-year-old children fed breast-milk or formula-milk as babies," The Lancet, vol. 141, pp.1319-1322.

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Last modified: Thu Nov 20 10:48:30 PST 1997