Micronutrient Interactions: Impact on Child Health and ... - Idpas.org

Iron–ascerbic Acid and Iron–calcium <strong>Interactions</strong> and Their Relevance in Complementary Feeding
premenopausal women were fed diets adequate
in iron (15 mg/day) and ascorbic acid
(>200 mg/day) for 12 weeks, the addition of
1000 mg of calcium as calcium carbonate
with meals produced no changes in serum
ferritin concentrations (Sokoll and
Dawson-Hughes 1992). However, the study
was relatively short and compensations in
the efficiency of iron absorption may have
occurred in the high-calcium group; iron
absorption was not measured directly. In the
longest experiment, which lasted 6 months,
daily supplements of 1200 mg calcium given
at meal times had no significant effect on
hemoglobin, serum ferritin, erythrocyte zinc
protoporphyrin, or serum transferrin receptor
concentrations in 11 nonanemic adults
(Minihane et al. 1997).
There is clearly a need for additional
studies of the long-term effects of high calcium
intakes on iron status. Such studies
should include infants and young children
with high iron requirements and low iron
intakes and stores. There are virtually no
studies of the influence of calcium on iron
absorption from complementary foods.
Neither is there clear evidence that supplemental
calcium during the period of complementary
feeding improves growth or bone
mineralization (Prentice and Bates, 1994).
Required Intakes of Iron,
Ascorbic Acid, and Calcium from
Complementary Foods
In a recent review for the World Health Organization
and the United Nations
Children’s Emergency Fund, we calculated
the amount of nutrients needed from
complementary foods for partially breastfed
infants aged 6–24 months (Brown et al.
1997). These calculations were based on the
difference between average reported intakes
of these nutrients by infants who continued
to be partially breast-fed and their estimated
nutrient requirements. The calculations revealed
that complementary foods (i.e., foods
other than breast milk) had to supply almost
all the iron and half the calcium requirement
of infants aged 6–24 months.
However, on average, ascorbic acid requirements
could still be met from the breast milk.
The only foods that could theoretically supply
enough iron were liver, fish, or beef, all
of which would have to be consumed in large
quantities. At ages 6–12 months, only dried
milk contained a density of calcium high
enough to provide the amount required in
complementary foods, whereas cheese, fresh
milk, and fish (canned or dried with bones)
could serve this purpose at ages 12–24
months.
Practical Implications for the
Complementary Feeding of
Infants
Practical implications for complementary
feeding, based on data presented here, are
as follows:
Because iron deficiency commonly develops
during the period of complementary
feeding when diets are typically
very low in iron, increasing the ascorbic
acid content of complementary
foods can be an important strategy for
improving iron absorption. Ascorbic
acid should be given with or included
in the meals that contain most iron or
consumed within 1 hour of meals.
Fortification with 50 mg ascorbic acid
can approximately double the amount
of iron absorbed from meals by infants.
At an iron–ascorbic acid molar ratio
of 1:2 or more, iron absorption is improved;
a ratio of 1:4 was optimal in
some studies.
Ascorbic acid produces the greatest increase
in iron absorption when complementary
foods are high in inhibitors
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