Neuroendocrinologist Thomas Badger
inserts a sample into a mass-
spectroscopy unit to measure
soy isoflavones in mammary
gland epithelial cells.
Studies at ACNC have shown
that animals fed diets high
in soy have a lower incidence
of breast cancer. Epithelial
cells are studied because they
are the cells that develop into
A mother and father have so many decisions to make for their newborn
babydecisions that can profoundly influence their boy's or girl's
development. The first decision they make might concern how to feed
their baby. After gathering facts on all the available options, different
parents reach different conclusions about what's best for their child.
ARS nutrition researchers in
Little Rock, Arkansas, hope to uncover more information to help parents
make this important decision. They're investigating the long-term effects
of soy infant formulaan increasingly popular feeding choice.
A 2000 Surgeon General's report found that 64 percent of American women
breast-feed during their infants' first weeks of life. But after 6 months,
that figure drops to 29 percent for many reasons.
Once a parent has chosen formula feeding, most pediatricians will recommend
cow's milk-based formula over soy-based formula for most babies. But
doctors will recommend soy formula if they believe an infant should
avoid cow's milk protein and/or lactose (milk sugar) or if the baby
simply doesn't tolerate milk-based formula. There are lactose-free milk-based
formulas available now, but some parents, including vegetarians, still
prefer soy-based formulas.
Research assistant Lisa Witcher
places a neural net on an
explaining the data
collection process to
the child's mother. The
neural net records brain
| Although soy infant
formulas are now consumed by 20-25 percent of formula-fed infants in America,
there is little research on the immediate and long-term health and cognitive
effects of this diet in humans.
A 1998 report from the American Academy of Pediatrics maintains that "isolated
soy protein-based formulas are safe and effective alternatives to provide
appropriate nutrition for normal growth and development" in term
infants not being fed breast milk or cow's milk-based formulas. But
some child-advocacy groups claim that consuming soy-based formula could
accelerate puberty and cause developmental and reproductive abnormalities
and thyroid disorders later in life.
Previous studies at ARS's Arkansas Children's Nutrition Center (ACNC)
in Little Rock and elsewhere found no apparent long-term positive or
negative effects of feeding infants soy versus cow's milk formula. But
there are no long-term, systematic studies of the effects of soy formula
on development, growth, and central nervous system function. To help
clarify the issue, Thomas M. Badger, ACNC director and a professor in
the College of Medicine at the University of Arkansas for Medical Sciences
(UAMS) in Little Rock, is leading a 6-year studybegun in September
2002to compare the effects of soy infant formula with those of
breast milk and cow's milk formula.
Psychological examiner Mindy
Lester (left) uses the Bayley
Scales of Infant Development
Assessment to conduct a
developmental assessment on
a 1-year-old girl. The
child's mother is pleased
to see her daughter's
progress since the previous
| Still, ACNC researchers
have found some reason to be concerned about possible drawbacks of soy
proteins: They could affect a body system involved in drug metabolism.
The scientists found that SPI-containing diets fed to young rats increase
activities of phase I and II detoxification systems, which are involved
with metabolizing toxins in the body. These beneficial systems can actually
remove substances that cause diseases such as cancer. But studies also
showed that soy consumption altered certain phase I enzymes found in
the liver, gut, and other organs. These enzymesin the CYP3A familyare
responsible for metabolism of about 80 percent of all clinical medications
taken by humans and other animals.
Martin J.J. Ronis, a toxicologist at ACNC and a professor at UAMS,
is conducting studies to see whether increased CYP3A could reduce drug
levels faster than normal and consequently reduce their beneficial effects.
High levels of these enzymes were found in rats fed large amounts of
soy, and even higher amounts were found after they were given medications.
Dual energy X-ray absorptiometry
(DXA) is used to measure
bone density and body
Janet Gilchrist analyzes
a DXA scan completed on
a 6-month-old boy.
"We found that SPI-fed rats had an increased phase I metabolism,"
Badger says. "This has two implications. First, these enzymes are
responsible for activation and deactivation of toxic materials, including
procarcinogens and carcinogens. This may be one mechanism by which SPI
reduces the incidence and number of mammary and colon cancers."Second,
since medications are also metabolized by these enzymes, it's possible
that drug efficacy is affected. We're currently studying this effect
in infants who are fed soy formula and comparing it to breast-fed and
milk formula-fed babies."
Bringing in Baby
Pat Wiggins and Jill Brackenbury, nutritionists at ACNC, are co-leading
the clinical portion of the ARS-supported infant study, which is building
on previous research at the center on the effects of soy in animals.
Known as the "soy twins"
in the study comparing
health effects of soy-based
formula, cow's milk-based
formula, and human breast
milk, these 8-month-old
boys take time out from
a busy study schedule to
enjoy a bottle of formula.
| "Soy-based formula has been
commercially available since the sixties," Wiggins says, "but
few studies have examined the long-term consequences of exposure to high
concentrations of estrogenic compounds during infancy. No one consumes
more soy per kilogram of body weight than infants who are fed soy-based
formula. Infants should consume about 115 calories per kilogram to maintain
Three hundred eighty full-term, healthy infants will participate in
the study at Arkansas Children's Hospital in Little Rock. Ninety-five
babies will be recruited in each of four groups. One group will be exclusively
breast-fed by their mothers; another group will be given milk-based
formula supplemented with docosahexaenoic acid (DHA), a fatty acid recently
made available in U.S. infant formulas; a third group will be given
soy-based formula with DHA; and a fourth group, soy formula without
DHA and another fatty acid, arachidonic acid, are found in small concentrations
in breast milk. They were not available in U.S. infant formulas until
2002. It's believed that DHA improves infant visual function and that
both compounds improve cognitive development, but more evidence is needed
to prove this.
ACNC conducted an extensive recruiting campaign throughout Little Rock
and the surrounding community. Some babies were enrolled as newborns.
Babies were selected on the basis of what their parents had already
decided to feed them. There were no efforts to persuade parents to feed
their babies a certain way.
The researchers start monitoring infants when they're about 1 month
old, checking for certain developmental milestones and collecting information
on diet, growth variables, medical history, and brain function.
Babies receive four brief health checks at 1, 2, 4, and 5 months of
age. They receive extensive checkups at 3, 6, and 9 months and 1 year,
then yearly until they are 6 years old. These longer evaluations include
a dual energy X-ray absorptiometry (DXA) scan to measure the children's
bone density and body composition. Badger says they expect to find that
early exposure to soy supports normal bone mineralization and improves
Also during the longer checkups, Terry Pivik and Roscoe Dykman, ACNC
psychologists and UAMS professors, study the effects of the diets on brain
function and on measures known to be predictive of later physical and mental
development, including school achievement. They do this by recording brain wave
activity from 128 different sites on each child's head as the child performs
various tasks. The dense array of recording sites makes it possible to localize
behavior to specific brain areas.
The researchers also gather information on sleep patterns, aspects of the
home environment and parental genetic influences, measures of IQ, and motor and
mental development, because these variables are also predictive of later mental
development and academic performance.
As they wean to regular food, the children undergo periodic examinations to
measure brain development and function. Says Badger, "We hope to determine
how various dietary factors affect cognitive function, learning ability, and
Perks of participating in the study include tests more thorough than the
ones most babies would ordinarily receive. Parents receive free formulaor
diapers if nursing. After 1 year, they receive $100 compensation for each
yearly examination. Most importantly, they receive detailed periodic reports on
the health of their babies.
Kim Jones of Conway, Arkansas, enrolled her daughter, Kaleigh, who is being
breast-fed, in the study in September 2002 when she was just 3 months old.
Jones believes taking part in the study will benefit Kaleigh a great deal.
"It's nice to have steady feedback on her growth," Jones says. "We'll
see how she is progressing and reaching her developmental milestones."By
Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS National Program (#107)
described on the World Wide Web at www.nps.ars.usda.gov.
Thomas M. Badger is with the
USDA-ARS Arkansas Children's Nutrition
Center, 1212 Marshall St., Little Rock, AR 72202; phone (501) 364-2785,
fax (501) 364-2818.
"Study Examines Long-Term Health Effects of Soy Infant
Formula" was published in the January 2004 issue
of Agricultural Research magazine.