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- Search for nutritional confounding
factors in the relationship between iron deficiency and brain
function.
- Hallberg L
- Am J Clin Nutr 1989 Sep 50:3 Suppl 598-604;
discussion 604-6
- Abstract
- This paper on confounding factors in the
relationship between iron deficiency and brain function is mainly
limited to nutritional factors, primarily factors that can contribute
to the development of iron deficiency and that may have an independent
direct action on brain function. Three theoretically possible
confounders were found in a systematic search for dietary factors:
1) low intake of ascorbic acid, 2) excess of phytates, and 3)
increased absorption of lead. Ascorbic acid has a marked effect
on the bioavailability of dietary iron and is also known to directly
influence various metabolic processes in the brain. Phytates inhibit
the absorption not only of iron but also of zinc. An iron deficiency
may thus be accompanied by a zinc deficiency which may affect
mental performance. A state of iron deficiency may increase the
absorption of lead from the diet, which in turn may affect brain
function.
- Soy protein, phytate, and iron absorption
in humans.
- Hurrell RF, Juillerat MA, Reddy MB, Lynch
SR, Dassenko SA, Cook JD
- Am J Clin Nutr 1992 Sep 56:3 573-8
- Abstract
- The effect of reducing the phytate in soy-protein
isolates on nonheme-iron absorption was examined in 32 human subjects.
Iron absorption was measured by using an extrinsic radioiron label
in liquid-formula meals containing hydrolyzed corn starch, corn
oil, and either egg white or one of a series of soy-protein isolates
with different phytate contents. Iron absorption increased four-
to fivefold when phytic acid was reduced from its native amount
of 4.9-8.4 to less than 0.01 mg/g of isolate. Even relatively
small quantities of residual phytate were strongly inhibitory
and phytic acid had to be reduced to less than 0.3 mg/g of isolate
(corresponding to less than 10 mg phytic acid/meal) before a meaningful
increase in iron absorption was observed. However, even after
removal of virtually all the phytic acid, iron absorption from
the soy-protein meal was still only half that of the egg white
control. It is concluded that phytic acid is a major inhibitory
factor of iron absorption in soy-protein isolates but that other
factors contribute to the poor bioavailability of iron from these
products.
- Iron bioavailability studied in infants:
the influence of phytic acid and ascorbic acid in infant formulas
based on soy isolate.
- Davidsson L, Galan P, Kastenmayer P, Cherouvrier
F, Juillerat MA, Hercberg S, Hurrell RF
- Pediatr Res 1994 Dec 36:6 816-22
- Abstract
- The influence of phytic acid and ascorbic
acid content of soy formula on iron (Fe) bioavailability was investigated
in infants by analysis of the incorporation of stable isotopes
of Fe into red blood cells 14 d after administration using a double
stable isotope technique. Paired comparisons were made with each
infant acting as his or her own control. The geometric mean fractional
Fe incorporation into red blood cells increased from 5.5 to 6.8%
(p < 0.05) when soy formula with the native content of phytic
acid was compared with a 83% dephytinized formula. A more pronounced
effect was shown with soy formula containing no phytic acid; the
mean fractional Fe incorporation increased from 3.9 (native phytic
acid) to 8.7% (zero phytic acid; p < 0.001). A significant
(p < 0.01) effect was also demonstrated when the Fe:ascorbic
acid molar ratio in the native phytate-containing formula was
increased from 1:2.1 to 1:4.2; mean fractional Fe incorporation
increased from 5.9 to 9.6%. These results demonstrate that the
Fe bioavailability from soy-based infant formulas can be similarly
increased by either removing phytic acid or increasing the ascorbic
acid content.
- A comparison of iron absorption in
adults and infants consuming identical infant formulas.
Hurrell RF, Davidsson
L, Reddy M, Kastenmayer P, Cook JD
- Br J Nutr 1998 Jan 79:1 31-6
- Abstract
- Fe absorption was estimated in adults and
infants from the erythrocyte incorporation of Fe isotopes added
to infant formula. Fe absorption was measured in adults using
radioisotopes, and in infants with a stable-isotope technique.
In adults, the geometric mean Fe absorption from a ready-to-feed
soya formula with its native phytic acid content was 2.4%. This
increased to 6.0% (P < 0.05) after almost complete dephytinization.
In infants, mean Fe absorption values were 3.9 and 8.7% respectively
from the same products (P < 0.05). In adults, mean Fe absorption
from a spray-dried soya formula containing 110 mg ascorbic acid/l
was 4.1%, increasing to 5.3% (P < 0.05) when ascorbic acid
was doubled to 220 mg/l. In infants, mean Fe absorption values
were 5.7 and 9.5% (P < 0.05) from the same products. Mean Fe
absorption from a milk-based formula was 6.5% in adults compared
with 6.7% in infants. All meals in the adult and infant studies
were fed using an identical meal size of 217 g. Increasing the
meal size threefold in adults did not change fractional Fe absorption.
Mean Fe absorption values for each meal were lower in adults than
in infants but the relative inhibitory effect of phytic acid and
the enhancing effect of ascorbic acid were similar. We conclude
that Fe absorption studies in adults can be used to assess the
influence of enhancers and inhibitors of Fe absorption in infant
formulas fed to infants. Further studies, however, are required
to extend these findings to weaning foods and complete meals.
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