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- Sandström B, Kivistö B, Cederblad A
- J Nutr 1987 Feb 117:2 321-7
- Abstract
- The absorption of zinc from soy protein-containing meals was
studied in healthy human subjects by means of extrinsic labelling
with 65Zn and whole body counting. Three types of soy protein,
a soy flour, a soy concentrate and a soy isolate, were used in
two types of meals: one consisting of rice and meat sauce and
the other of white or whole-meal bread. Thirty and 100% of the
protein of the meat sauce and 50% of the protein of bread was
replaced with the soy protein products. Replacement of 30% of
the protein in meat sauce had a marginal effect on the percentage
absorption of zinc, whereas the absolute amount of zinc absorbed
was lower due to the lower zinc content in soy products than in
meat. After total replacement of the meat protein, a significantly
lower percentage and absolute absorption of zinc was observed.
A lower absorption of zinc was observed when soy protein was added
to white bread. The absorption of zinc from the whole-meal bread
was low and did not change when 50% of the flour protein was replaced
by soy protein. We conclude that the effect of soy protein on
zinc absorption depends on the degree of replacement, the phytic
acid and zinc content of the soy product and the protein content
of the meal.
- Lönnerdal B, Bell JG, Hendrickx AG, Burns RA, Keen CL
- Am J Clin Nutr 1988 Nov 48:5 1301-6
- Abstract
- Low zinc bioavailability from soy formula may be the result
of the formula's phytate content. We assessed the effect of phytate
removal from soy formula on Zn absorption using infant rhesus
monkeys and suckling rat pups as animal models. Zn absorption
in monkeys, as determined by whole-body counting, was 65% from
human milk, 54% from monkey milk, 60% from whey-predominant formula,
46% from casein-predominant formula, and only 27% from conventional
soy formula (0.621 mmol phytate/L). In contrast, Zn absorption
from dephytinized soy formula (0.067 mmol phytate/L) was 45%.
In suckling rats, Zn absorption from conventional soy formula
was only 16% vs 47% from dephytinized soy formula. Phytate concentration
in a variety of experimental soy formulas was inversely correlated
to Zn absorption. These results suggest that the low bioavailability
of Zn from soy formula is a function of its phytate concentration
and can be overcome by the removal of phytate.
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