Formula Contents
As he writes (Pediatrics 2003;111:1017-23), most
infant formulas contain palm and palm olein (PO) oils as their main source of
fat. Manufacturers add these oils to their formulas in an attempt to better
match the composition of human milk, specifically, its high palmitic acid
content—by weight, about 20% of total fatty acids. Over the past few years,
some researchers have come to appreciate that the structure of palmitic acid in
human milk is different from that of a vegetable source and formulas containing
PO have been found to have unanticipated consequences.
In one study comparing formulas with different amounts of
palmitic acid, Lucas et al. (Arch Dis Child Fetal Neonatal Ed 1997;77:F178-F184)
found that infants fed a formula that had high amounts of palmitic acid that
behaved in the same way as palmitic acid does in breast milk absorbed more fat
from the formula than infants fed formulas containing less fat in the
"right" configuration. Another study comparing the effect of a PO
formula vs. another formula with a very similar fat makeup but which contained
no PO also found that infants fed the PO formula absorbed significantly less
fat than they did when fed the PO-free formula (JACN 1998;17(4):327-32).
In the same study, investigators also observed infants fed the PO formula
excreted more calcium in their stools than when fed the PO-free formula, a
signal that infants absorb less calcium when fed a PO formula
Infant Bone Mineral and Calcium
These findings have been replicated by other researchers but
do these differences in fat and calcium absorption make any meaningful
difference in the infant’s development? The answer is quite possibly
affirmative. In Dr. Koo’s own study, infants were fed one of two commercially
available infant formulas, starting two weeks after birth until the age of six
months. The main difference between the formulas tested was that one contained
PO and the other did not. Investigators then measured the degree of bone
mineralization both at the time the study started and then again at three and
six months of age.
Out of approximately 100 infants who finished the study, Dr. Koo found that
infants fed the formula containing PO had significantly lower bone mineral
content (BMC) than those who received the PO-free formula. The difference in
BMC seen in this study between the two formula groups meant that if infants are
fed a formula containing PO, they would need to receive an additional 200 mL of formula a day to achieve
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the same gain in bone mass
as infants fed a formula without PO.
More importantly, as Dr. Koo indicated, skeletal growth is
extremely rapid during infancy. Thus, strategies that bolster calcium absorption
and increase bone mass would seem to make sense as an important nutritional goal
for all infants, as he suggested. Infants who excrete more calcium as a result
of being fed formulas that do not exactly mimic the way fats work in breast milk
also excrete harder stools. In another comparison of a standard formula vs. a
formula containing high amounts of palmitate similar to that in breast milk,
infants receiving the more breast milk-like formula again had higher BMC than
those on standard formula. They also had softer stools because they excreted
less calcium than infants fed a standard formula.
Gastrointestinal Effects
The real goal in the development of infant formulas is to
make one that is as well tolerated as breast milk. In an effort to demonstrate
that some formulas are better tolerated than others, Gil-Alberdi and colleagues
evaluated the gastrointestinal (GI) tolerance of Similac, a non-PO-containing
formula with total potentially available nucleosides (TPAN), maternal milk or
other formulas on the market at the time (Nutr Hosp 2000;15(1):21-31).
Results showed that GI intolerance was reduced by more than half when infants
were fed the TPAN formula compared with other formulas. Indeed, rates of GI
intolerance were low and virtually identical between infants receiving the TPAN
formula and those receiving maternal milk.
Not all types of supplementation used in infant formulas have
unintended effects. Indeed, there is ample evidence that dietary nucleotides
affect the maturation of an infant’s immune system, thereby potentially
affording earlier benefit against various illnesses. Nucleotides are also felt
to mitigate against suppression of the immune system associated with
malnutrition and increase resistance to some bacterial and fungal pathogens.
Perhaps the most important action of dietary nucleotides rests in their ability
to reduce the risk of diarrhea. As reported by Yau et al. (J Pediatr
Gastroenterol Nutr 2003;36(1):37-43), infants between the ages of one and
seven days were randomized to receive an infant formula fortified with
nucleotides or to a control formula. Infants remained exclusively on either
formula until 12 weeks of age, and then received solid food in addition to the
assigned formula. The formula fortified with nucleotides contained 72 mg/L of
nucleotides, similar to that of human milk. |
