BREASTFED babies tend to be brighter than those fed by bottle. But many
experts now claim that the disparity in brainpower could be reduced by adding a
couple of mundane ingredients to infant formula. Dennis Hoffman, Eileen Birch
and their colleagues at the Retina Foundation of the Southwest in Dallas, Texas,
have tested the effects of adding the simple fatty acids docosahexaenoic acid
(DHA) and arachidonic acid (AA) to infant formula and have just published their
conclusion that the supplements aid mental development in bottle-fed babies.
But rather than settle an important issue on infant nutrition, this study has
reignited a long-running feud about whether or not the ingredients should be
added to infant formulas. Some earlier studies found no beneficial effects. And
in 1998, the US Food and Drug Administration warned that 鈥渢he potential
short-term and long-term effects of these substances have not been sufficiently
characterised in infants鈥�.
Compared with Europe, a large percentage of babies in North America are
bottle-fed (see Diagram).
The supporters of AA/DHA supplements believe hundreds
of thousands鈥攑erhaps even millions鈥攐f American babies could be
failing to realise their true intellectual potential.
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While the acids are excluded from formula milk in the US and Canada, European
babies have received the supplements in their bottle milk since the mid-1990s,
when the European Scientific Committee on Food approved them. Not surprisingly,
the nutrition manager of bottle-feed producer Milupa told 快猫短视频
that the latest research backed its contention that the addition of AA and DHA
to infant milk is a safe and effective way to boost babies鈥� mental development.
However, not all Britain鈥檚 suppliers of formula milk add the supplements
routinely.
The logic of adding the acids seems sound: both are already present in breast
milk, and both are structural components of the brain鈥檚 grey matter, the retina
of the eye and the fats that sheathe nerves. Unfortunately, paediatricians don鈥檛
agree on whether the supplements are vital for the early development of the
infant brain. Some believe babies can make their own DHA and AA from
alpha-linolenic acid and linoleic acid respectively, two fatty acids routinely
added to formula milk. Nor is there consensus on the safety of these
supplements.
The FDA report describes the evidence so far as 鈥渋nconsistent鈥�, and it plans
to 鈥渞evisit鈥� the subject in 2003. Meanwhile, a 1998 report for Canada鈥檚 health
ministry reached a similar verdict, concluding that 鈥渢he routine addition of
these nutrients to formulas designed for full term infants is not
谤别肠辞尘尘别苍诲别诲鈥�.
But the Dallas study revives hope for backers of supplementation. Birch and
her colleagues split 56 infants into three roughly equal groups. One received
standard formula milk supplemented with DHA and AA. The second drank milk with
DHA added, and the third had plain formula.
All the mothers switched to ordinary milk at four months. Proponents of the
supplements believe that it can take this long for babies to start making their
own DHA and AA. As a result, babies risk a deficit in their brain development
compared with breastfed babies during their first four months.
When the babies reached 18 months, the researchers subjected them to a
standard battery of infant intelligence tests called the Bayley Scales of Infant
Development. These measure the cognitive development of infants on a scale
called the mental development index, or MDI. Just as with IQ tests given to
older children and adults, 100 is an average score from the tests, which consist
of a mixture of mentally taxing puzzles, tasks and games.
Infants fed with DHA and AA achieved significantly higher scores than both
other groups, averaging 105 on the MDI scale compared with 98 for the control
group and 102 for the infants fed milk with just DHA added (Developmental
Medicine & Child Neurology, vol 42, p 174).
鈥淥n an individual basis, seven points is not much,鈥� says Hoffman. 鈥淏ut
averaged over a whole population, that could be very significant.鈥� It is similar
to the typical five-point difference seen when breast-fed and bottle-fed babies
are compared.
Of the 19 infants fed both acids, five scored higher than
115鈥攃onsidered to be accelerated performance. Only one infant from each of
the other groups exceeded 115. None of the infants in the supplemented groups
scored lower than 85, which would be suggestive of 鈥渄elayed performance鈥�,
whereas two fell below this threshold in the plain formula group.
The researchers also found evidence to back the idea that the supplements are
vital in the first, critical four months of brain development. They found that
MDI scores tallied with levels of DHA in blood samples taken at four months, but
that MDI scores did not correlate with blood levels at 12 months. 鈥淚n other
words, the levels at four months were crucial to what the children could do at
18 months,鈥� says Hoffman.
Alan Lucas of the Institute of Child Health in London agrees that a
seven-point difference would be big news. 鈥淪even points on the MDI is huge . . .
and equates to about 10 per cent of the variation in the population,鈥� he says.
But he cautions that the study is so small that it lacks the statistical power
to rule out chance findings. 鈥淭he only important thing to note is that it鈥檚 an
extremely small study, with a mean population size of around 18 subjects per
treatment group,鈥� he says.
Last December, Lucas and his colleagues published a study in The
Lancet (vol 354, p 1948) of infants born at hospitals in central England,
the largest trial of this kind ever done. The research involved 447 infants, 155
on standard formula, 138 breastfed as controls, and 154 on formula supplemented
with DHA and AA. They found that children had roughly the same Bayley scores at
18 months, whichever group they were in. So there seemed to be no obvious
benefits from adding the supplements.
Sheila Innis, professor of paediatrics at the University of Columbia in
Vancouver, also points out that if milk is a key to mental development, then
there are plenty of factors other than DHA and AA which might be important, such
as hormones and growth factors found in breast milk.
To an extent, the criticisms are accepted. 鈥淲hat we need are larger sample
sizes,鈥� says Hoffman. The Dallas team is now preparing to do such larger trials,
as well as follow-up studies on the original infants, who are now four years
old.
Other researchers who back the addition of DHA and AA to milk are delighted
with Hoffman鈥檚 findings. 鈥淚t鈥檚 consistent with results we got in a similar kind
of study in 1998,鈥� says Peter Willatts of the department of psychology at the
University of Dundee. 鈥淲e tested children at 10 months, and the group on
supplementation were producing twice as many solutions to the problems as the
controls,鈥� he says (The Lancet, vol 352, p 688).
Willatts agrees with Hoffman that the seven-point difference could make a
huge difference across an entire population although pre-existing intellectual
disparities would remain even if all bottle-feeders had the acids. 鈥淏ut at the
lower end, you might have the difference between a child who has difficulty
reading but who could be nudged over that boundary,鈥� he says.
If safety is a real concern, then withholding the products makes sense. But
supporters claim the vast body of evidence suggests that they are safe when
given in the recommended doses. Even researchers like Lucas, who are sceptical
about their effectiveness, can find no evidence that they do harm.
The issue reinforces the old adage that 鈥渂reast is best鈥�. But for bottle-fed
babies in the US, perhaps the FDA鈥檚 planned 鈥渞evisiting鈥� of this subject can鈥檛
come soon enough.