Iron absorption II. Role explain Hallberg,2
Southeast
of various factors low absrption1 E.
Bj#{246}rn-Rasmussen,3
L.
ABSTRACT
Previously
meals
of
composed
prevalence
of
systematically such
iron
as certain
subjects
foodstuffs, from
of a small
were
of the
labeled
identified meals
nonhomogenized an average
both
dose
before
mg)
and
socioeconomic
groups
to measure
the
and
and
was
of Thais
determination
the
consistent mainly
simpler
but
the
cause
of
the
consuming
meal
flour
was
in Thai
actual
absorption
also
more
from
of rice. of iron
meals
studied.
composite
was
in the diet
characteristics Swedish the Iron
of the
by comparing women
using
Two
main
homogenization absorption times
have
J. Clin. Nutr.
from
higher
deficiency Recent
meals
known
absorption factors
was many
prevalence
Am.
low
Asian
the
of comparison.
studies:
instead
accurate.
with
excluded
and
basis
previously
the simple
iron
the and
latter
in the previous as studied
Southeast
errors,
absorption The
rice
use of rice with
common
to be consistent
as a common
absorption
composition
nonheme
the
iron.
ascorbate
from
low
methodological
a composite
the low
of identical
of the method made
rolls
serving
paper
inhibiting
of ferrous
as causing
meals 0.16
wheat
too
comprised of dietary
Suwanik5
absorption
were
present
or contaminants
the
factors
the
R.
of iron
spices
investigated
by malabsorption
the absorption absorption
In
.
Variables
accompanied
and
diets
might
and
levels
vegetables,
deficiency
sought.
that
Rossander,4
reported
rice,
Asian
(on
in lower
modifications thus
not
only
30: 539-548,
1977.
In an earlier study to establish the diet in the high prevalence
the role of of iron defi-
ciency in Southeast Asia it was found the absorption of iron from a simple composed of rice, cooked vegetables,
spices was very low (1). A low iron tion from such a meal was expected type
of meal
is especially
common
that meal and
absorpas this in those
segments of the population in which iron deficiency is common, and as pathological iron losses attributable to hookworm infestation, if present, in most areas are reported to be negligible (2). The absorption from this simple diet, however, was much lower than expected and would actually imply that subjects
mainly
consuming
such
a diet
but
The American
also
the Journal
experimental of Clinical
conditions Nutrition
to establish are present.
In the previous
whether
study
any
systematic
all foodstuffs
in the
meals
served were carefully minced and mixed in order to facilitate isotopic exchange between the native iron in the foodstuffs and the radioiron added. This led, however, to the meals having an appearance and a consistency that differed from normal meals and some subjects had difficulty consuming the meals and needed more time than usual to finish them. A hypothesis was put forward in the earlier paper, that the
meals
in the form
in which
they
were
served
could
only maintain their iron balance in a state of iron deficiency. The actual iron status of the population consuming such a diet, however, is not as unsatisfactory as the absorption data imply. In the systematic search for the cause of the low absorption there is therefore reason to study not only the properties of the diet and factors relating to the subjects
order errors
30: APRIL
in
From the Department of Medicine, University of Goteborg, Sahlgrenska sjukhuset, GOteborg, Sweden and the Siriraj Hospital and Medical School, Mahidol University, Bangkok, Thailand. This work was supported by WHO and the Swedish Medical Research Council (project No B77-1 9X-04721-02). 2 Professor of Medicine, University of G#{246}teborg. Assistant Professor of Medicine, University of GOteborg. Nutritionist, University of Gateborg. Professor of Radiology, Siriraj Hospital and Medical School, Mahidol University.
1977,
pp. 539-548.
Printed
in U.S.A.
539
Downloaded from https://academic.oup.com/ajcn/article-abstract/30/4/539/4650317 by guest on 09 November 2018
L.
from
540
HALLBERG
were not capable of fully eliciting the cephalic phase of gastric secretion . Recent studies have shown that it is possible to label a meal validly without homogenization (3). In the present studies comparisons were therefore made between the absorption from the same food served in the usual way and as a homogenized
meal.
These
meals
had
the
same
is common
in the
population
studied
as in-
testinal biopsy studies have shown that clubbing of the intestinal viii, suggestive of a sprue syndrome , is widespread among apparently healthy subjects (4). In order to obtain some information about whether Thai subjects have a lower ability to absorb food iron than subjects in nontropical areas a direct comparison was made between the iron absorption in Thai and Swedish women from two kinds of meals using the absorption of ferrous sulfate as a basis for comparison. The role of the diet itself in the low absorption may need extensive studies. In the present investigation two kinds of studies were made studies on the role of the main components rice, vegetables, and spices, -
and studies nants. The
on the role latter studies
of food contamiwere carried out
because the iron content of the meals in the earlier study was much higher than expected from food tables. TABLE Iron and
1 phosphorus
Study
content
of meals
no.
and
their
corn ponents
Subjects
Fifty-two
female
nursing
Experimental The studies
VI
V
washed and VII
VI unwashed
Wheat rolls Rice Vegetables and Total Rice Vegetables and Total Vegetables
and
Rice porridge Chilirnix Total
IX
curry
Rice Total
VIII
curry
Rice
porridge
Vegetable Total
mix
curry
nurses at
design
present investigation comprised (see Table 1). In 4 series (I to IV)
solution
of ferrous
ascorbate
nine series, of a meal A or a
B was consumed
after
fasting overnight on four consecutive mornings in the sequence ABBA or BAAB . The meals and the ferrous ascorbate were labeled with two different radioiron isotopes (Fe and Fe) and a blood sample was drawn 2 weeks after the last serving in order to measure the iron absorption from the meal and the reference iron solution. This design was used to study the absorption of iron from wheat rolls and a composite Thai-meal in Thai and Swedish women. In one series (V) in Thai women two kinds of meals were compared . They were identical in all respects except that one was carefully minced and mixed whereas the other meal was served in the usual way. The meals were prepared from the same batches of raw materials. The two meals, called A and B, were labeled with two different radioiron isotopes and were served on four consecutive mornings, the subjects having fasted overnight, in the sequence ABBA or BAAB. Two weeks later a blood sample was drawn to determine the absorption of the two radioiron isotopes. In two series (VI and VII), aimed at studying the effect of iron contamination on iron absorption , two kinds of meals were compared as above. After the blood sample had been drawn to determine radioiron
absorption, beled
with
(amount
however,
a ferrous
radioiron
was
pe r meal
given
ascorbate in the
serve d) in the
water
solution
fasting
different
la-
state
studies
Phoaphorua
.
mclud-
Iron Total P
Phytic
mg
g
I, II III, IV,
aides and student
Siriraj Hospital in Bangkok and 25 female and six male medical students in Goteborg served as volunteer subjects. They all considered themselves healthy. Hematological evaluations and other data are given in the tables.
weight . ing
Food
and methods
Material
104 175 87 262 175
1.2 0.44 2.45 2.89 0.30
66 53 43 96 34
87
1.62
38
262 175 87 262 338 3 341 336 58 394
1.92 0.44 3.71 4.15 2.57 1.78 4.35 3.36 1.28 4.64
72 44 41 85 83 2 85 94 25 119
0 33 0 33
39 0 39 47 0 47
P
on
Downloaded from https://academic.oup.com/ajcn/article-abstract/30/4/539/4650317 by guest on 09 November 2018
ingredients and the same relative composition as the basal meals in the previous study. It has been suggested that malabsorption
AL.
ET
ABSORPTION
IRON two
mornings
to determine
the subject’s
FROM
ability
to ab-
sorb iron. The absorption of iron from the ferrous ascorbate solutions was calculated from measurements on a new blood sample drawn 2 weeks after the last oral dose. In two series (VIII and IX) the roles of the three main components of the basal diet - rice , vegetables and spices - were investigated to explain the low ab-
sorption.
In series VIII
rice flour
sign as in series
V. The chili
of a boiled
without the same chili reported study using same experimental de-
mix was identical
to that
ASIAN
DIETS
541
meals were prepared at the same time . The rice was steam-boiled for 25 mm. It was then left standing at room temperature for about half an hour and then minced in a high-speed mixer to form a homogenous paste
.
The
and then water.
vegetables
minced
A final
the vegetable
were
steam-boiled
for
in the same high-speed
mixture
mix,
was then
the chili
made
paste,
fish sauce . Radioiron was added amounts corresponding to 6CiFe Weighed amounts (300 g) of the were put into aluminum forms that a freezer. On the afternoon before num forms were removed from the
1 5 mm
mixer
of the rice
with paste,
coconut cream, and at this stage in to each subject. homogenized meal were then placed in serving, the alumifreezer and on the
used in the previously reported study, having been kept frozen at -20 C in the laboratory. In series LX the vegetable mix was studied in the same- way as the chili mix. The vegetable mix was also identical to the mix used in the previously reported study and had been kept frozen in the laboratory. The composite rice meals in study III, IV, V, VI, and VII had the same relative composition as the basal meals in the previously reported studies . Every detail in
times in tap water. The vegetables were washed in running tap water before being chopped into small pieces in the usual way. The unwashed meals were
the previous chili mix etc
prepared washed
protocol
was followed
in preparation
of
the only exceptions were the washing of the foods in study VI and VII and the homogenization in study V as described in the next section . Compared with the previous study the amount of food in each .
meal was reduced by 25 % in order to facilitate every subject could fully consume their meals.
that
morning just before serving, they for 1 5 mm in a pressure cooker.
from rice and vegetables that were not at all . The soil that was added to half of the
meals in study VII was obtained from rice fields outside Bangkok. Lumps of dry soil were placed in a porcelain mortar and finely ground. Any large particles were removed.
The
200 C. Using
of food
The wheat rolls in studies I and II were made in Sweden. A single batch of labeled rolls were baked in Sweden , and kept frozen until the day before serving. They were transported to Thailand and were kept frozen until the day before serving. The rolls were baked from unfortified white wheat flour, 60 % extraction. Each roll contained 30 g of wheat flour and had an iron content of 0.6 mg, of which 0.25 mg was added as ferrous sulphate . Two rolls were served each time . The total intake of four rolls in each subject corresponded to an intake of 3 sCi55Fe . The Thai meal, which was served to both Thai and Swedish women (study III and IV), was prepared in an identical manner for both groups of women from the same batches of raw materi-
als that were transported
deep-frozen
to Sweden
from
Thailand. The composite rice meals in the different studies were prepared in the same way, if not otherwise indicated, by weighing 50 g of carefully washed rice in an aluminum form adding 125 ml of distilled water and 2 ml of a radioiron solution. The form was covered with a lid and cooked under pressure (+0.5 kg/cm2) in a steam cooker for 25 to 30 mm. The vegetables were carefully washed and then finely chopped. Weighed amounts were put into another aluminum form together with a measured amount of a warm mixture of chili paste, fish sauce, and coconut cream. One milliliter of the radioiron solution was then added and the form was covered with a lid and cooked under pressure (+0.5 kg/cm2) in a steam cooker for 20 mm. The homogenized meals in study V were prepared at one time from the same batch of rice and the same batches of finely chopped vegetables, chili paste, etc. as
was used in the nonhomogenized were the same as used in study
meals. These batches III and IV and all these
steam-heated
In studies VI and VII the same batches of foods were used for preparing all meals. The washed meals were prepared from rice that was carefully washed 3
weighed Preparation
were
into
soil was then put into an oven for 2 hr at an analytical balance 200 mg of soil were small glass tubes corresponding to the
amount added to each meal. The soil was added to the vegetables and rice before cooking and was carefully mixed into the food with a glass rod . The chemical properties of the soil are reported later in this paper . In studies VIII and IX the meals were homogenized and prepared in exactly the same way as in the previously reported study. The vegetables and chili mix used were identical to those used in that study, having been kept
frozen in the laboratory until the present study. The amount of chili mix (paste) was smaller, however, as the Swedish subjects had difficulties taking the same amount as the Thai subjects. The only difference between the present and the earlier studies was the rice flour
that
bought
was
made
in Sweden
content of each 5 mg by adding Chemical
in
the
laboratory
in a Culatti
meal in these two ferrous sulphate
composition
mill. series before
by
The
milling
total
was adjusted cooking.
rice
iron to
of meaLs
Aliquots of the meals and/or their components were freeze-dried and then finely ground to a powder in a porcelain mortar. Weighed amounts of this powder were used for the analyses of iron (5), phosphorus (6), and phytic acid phosphorus (7). The chemical composition of the meals is given in Table 1. Serving
the meals
All meals were served under supervision in the morning, the subjects having fasted overnight. The sequence of serving the different meals or the reference solutions is given in the section on experimental design. The meals or the bread were eaten together with 200 ml of distilled water. All food and the water served were consumed.
Downloaded from https://academic.oup.com/ajcn/article-abstract/30/4/539/4650317 by guest on 09 November 2018
porridge was served with and mix as was used in the previously two radioiron isotopes and the
in the form
SOUTHEAST
542 Oral
doses
offrrrous
iron
ascorbate
A solution of 10 ml 0.01 M hydrochloric acid contaming 3 mg of iron as ferrous sulphate , 30 mg of ascorbic acid and 1 .4 Ci59Fe was used as a reference in all studies except studies V. VIII, and IX. Each
subject
was given
2 doses, taken
on two mornings. The solutions from test tubes, which were then
distilled
water
of the
were rinsed
that was also consumed
under
supervi-
staff.
Absorption
measurements
Calculations
the
absorption
of
and the reference
solution
were
surements of 59Fe and samples and standard scribed previously (1).
Fe in solutions
blood using
meals
overnight
taken directly four times with
Properties
of
ofsoil
iron
from
based
containing
1 mg of Fe/mi
was added,
0.90
the
on mea-
samples, methods
solution
mg of iron and 70% of the radioiron was found in the solution after 2 hr. When the pH was reduced to 2.4 by using 0.01 M of hydrochloric acid instead of 0.001 M, 0.11 mg of iron was dissolved from the soil. After adding the iron solution 1.05 mg of iron and 83% of the radioiron was found in the solution after 2 hr. Calculated from the change in specific activity of the radioiron, 70% had exchanged with the soil iron at both the lower pH levels whereas there was no exchange between soil iron and the added iron at neutral pH. At this pH level there was merely an adsorption of iron onto the soil.
food de-
used
study the ability of the soil used in study VII to take up iron , various amounts of dried powdered soil were put into test tubes. Ten milliliters of distilled water and then 1 ml of a freshly prepared solution containing I mg of ferric iron (as ferric chloride) in 0.001 M hydrochloric acid and a trace amount of 29FeCl were added. The tubes were shaken for 15 mm. After centrifugation at 3,000 x g for 10 mm the concentration of iron and radioiron was determined in the supernatant. The results were expressed as a percentage of the values in a test tube containing no soil. The uptake of iron and radioiron in relation to the amount of soil added is shown in Figure 1. The same uptake of iron and radioiron was obtained using 200 mg of soil when the volume of the solution was 200 ml instead of 10 ml. The pH of the aqueous solution of iron and soil after 20 and 40 mm was 8.2 and 7.1, respectively. When soil and water were mixed no iron was found in the solution. When 200 mg of soil was mixed with 200 ml of 0.001 M hydrochloric acid (pH of the solution 4.3) 0.04 mg of iron was dissolved within 2 hr. The iron content of the soil was 2.27g/l00 g of dry soil. When 1 ml of the same radioiron-labeled
Other
methods
Hemoglobin was determined as cyanomethemoglobin and hematocrits were spun in an International Microchematocrit centrifuge. Both determinations were carried out on one venous blood sample drawn into a heparin tube using a minimum of stasis.
To
IRON
Results Studies
I and
II
Comparison of the absorption of from wheat rolls and ferrous ascorbate Thai and Swedish women. The results
iron in
are given in Table 2. It is evident that the absorption of iron from wheat rolls was about the same in Thai and Swedish women. The higher average absorption from wheat observed in the Swedish women was accompanied by a higher absorption from the ferrous ascorbate solution also. This is probably attributed to differences in iron status between the subjects illustrates the value
from
a reference
in the two groups and of using the absorption
inorganic
iron
salt
as
details
see text.
UPTAKE
50
50
100
200
300
400
600
800
1000 mg
FIG.
1.
Uptake
of iron
and
radioiron
by the soil in relation
to the amount
clay
of soil added.
For
a
Downloaded from https://academic.oup.com/ajcn/article-abstract/30/4/539/4650317 by guest on 09 November 2018
sion
after fasting
AL.
ET
HALLBERG
IRON
ABSORPTION
FROM
SOUTHEAST
.
ASIAN
DIETS
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+1
U
544
basis
HALLBERG
for
absorb Figure
. The similar ability in the two groups is illustrated
AL.
%
to in
comparison
iron 2.
ET
20 C
0
0
0
15
Studies
III
and
IV
o0
/
10
/ / /
Comparison of the absorption of iron a composite Thai meal and from ferrous abscorbate in Thai and Swedish women. The results are given in Table 2.
0
fr om
ratio
between
and
ferrous
cantly
0 .01)
different
The
.
groups Study
the
absorption
iron
was in
food
the
from
Figure
40
60
of reference
Thai Swedish
80 (Fe504)
1#{243}0% 3
mg
Fe
FIG. 3. Iron absorption from a simple Thai meal of rice, cooked vegetables, and from ferrous ascorbate (3 mg of Fe) in Thai ish women.
composite spices and and Swed-
iron
statistically signifitwo groups (P < between the two
difference
is evident
of
20 Absorption
0 ti
Absorption Homogenized meal
3.
V
Comparison of iron absorption from a composite Thai meal served in the usual way and in homogenized form. In eight of the 10 subjects a higher absorption was obtained
from erage these was results Study
the nonhomogenized meals. On an av70% more iron was absorbed from meals. The effect of homogenization statistically significant (P < 0.01). The are
shown
in Figure
4.
VI
FIG. 4. Iron Thai meal served
absorption from in the usual way
%
a simple composite and in homogenized
form.
Comparison prepared from
The
as a graph
Absorption
of absorption washed and
percentage
between unwashed
meals foods.
was
slightly
absorption
higher washed tically
from the washed than from the unfoods. The difference was not statissignificant (P > As the iron 0.05).
content
%
0
50
higher
in
the
meals
from unwashed foods, however, of iron absorbed was greater
//
40
was
0
meals
(see
Study
VH
prepared
the amount from these
“Discussion”).
., 30 0
0
The effect on the iron absorption soil to a composite Thai meal. previous study the percentage
C
220 c36
I
o Thai subjects Swedish subjects
Southeast
of various factors low absrption1 E.
Bj#{246}rn-Rasmussen,3
L.
ABSTRACT
Previously
meals
of
composed
prevalence
of
systematically such
iron
as certain
subjects
foodstuffs, from
of a small
were
of the
labeled
identified meals
nonhomogenized an average
both
dose
before
mg)
and
socioeconomic
groups
to measure
the
and
and
was
of Thais
determination
the
consistent mainly
simpler
but
the
cause
of
the
consuming
meal
flour
was
in Thai
actual
absorption
also
more
from
of rice. of iron
meals
studied.
composite
was
in the diet
characteristics Swedish the Iron
of the
by comparing women
using
Two
main
homogenization absorption times
have
J. Clin. Nutr.
from
higher
deficiency Recent
meals
known
absorption factors
was many
prevalence
Am.
low
Asian
the
of comparison.
studies:
instead
accurate.
with
excluded
and
basis
previously
the simple
iron
the and
latter
in the previous as studied
Southeast
errors,
absorption The
rice
use of rice with
common
to be consistent
as a common
absorption
composition
nonheme
the
iron.
ascorbate
from
low
methodological
a composite
the low
of identical
of the method made
rolls
serving
paper
inhibiting
of ferrous
as causing
meals 0.16
wheat
too
comprised of dietary
Suwanik5
absorption
were
present
or contaminants
the
factors
the
R.
of iron
spices
investigated
by malabsorption
the absorption absorption
In
.
Variables
accompanied
and
diets
might
and
levels
vegetables,
deficiency
sought.
that
Rossander,4
reported
rice,
Asian
(on
in lower
modifications thus
not
only
30: 539-548,
1977.
In an earlier study to establish the diet in the high prevalence
the role of of iron defi-
ciency in Southeast Asia it was found the absorption of iron from a simple composed of rice, cooked vegetables,
spices was very low (1). A low iron tion from such a meal was expected type
of meal
is especially
common
that meal and
absorpas this in those
segments of the population in which iron deficiency is common, and as pathological iron losses attributable to hookworm infestation, if present, in most areas are reported to be negligible (2). The absorption from this simple diet, however, was much lower than expected and would actually imply that subjects
mainly
consuming
such
a diet
but
The American
also
the Journal
experimental of Clinical
conditions Nutrition
to establish are present.
In the previous
whether
study
any
systematic
all foodstuffs
in the
meals
served were carefully minced and mixed in order to facilitate isotopic exchange between the native iron in the foodstuffs and the radioiron added. This led, however, to the meals having an appearance and a consistency that differed from normal meals and some subjects had difficulty consuming the meals and needed more time than usual to finish them. A hypothesis was put forward in the earlier paper, that the
meals
in the form
in which
they
were
served
could
only maintain their iron balance in a state of iron deficiency. The actual iron status of the population consuming such a diet, however, is not as unsatisfactory as the absorption data imply. In the systematic search for the cause of the low absorption there is therefore reason to study not only the properties of the diet and factors relating to the subjects
order errors
30: APRIL
in
From the Department of Medicine, University of Goteborg, Sahlgrenska sjukhuset, GOteborg, Sweden and the Siriraj Hospital and Medical School, Mahidol University, Bangkok, Thailand. This work was supported by WHO and the Swedish Medical Research Council (project No B77-1 9X-04721-02). 2 Professor of Medicine, University of G#{246}teborg. Assistant Professor of Medicine, University of GOteborg. Nutritionist, University of Gateborg. Professor of Radiology, Siriraj Hospital and Medical School, Mahidol University.
1977,
pp. 539-548.
Printed
in U.S.A.
539
Downloaded from https://academic.oup.com/ajcn/article-abstract/30/4/539/4650317 by guest on 09 November 2018
L.
from
540
HALLBERG
were not capable of fully eliciting the cephalic phase of gastric secretion . Recent studies have shown that it is possible to label a meal validly without homogenization (3). In the present studies comparisons were therefore made between the absorption from the same food served in the usual way and as a homogenized
meal.
These
meals
had
the
same
is common
in the
population
studied
as in-
testinal biopsy studies have shown that clubbing of the intestinal viii, suggestive of a sprue syndrome , is widespread among apparently healthy subjects (4). In order to obtain some information about whether Thai subjects have a lower ability to absorb food iron than subjects in nontropical areas a direct comparison was made between the iron absorption in Thai and Swedish women from two kinds of meals using the absorption of ferrous sulfate as a basis for comparison. The role of the diet itself in the low absorption may need extensive studies. In the present investigation two kinds of studies were made studies on the role of the main components rice, vegetables, and spices, -
and studies nants. The
on the role latter studies
of food contamiwere carried out
because the iron content of the meals in the earlier study was much higher than expected from food tables. TABLE Iron and
1 phosphorus
Study
content
of meals
no.
and
their
corn ponents
Subjects
Fifty-two
female
nursing
Experimental The studies
VI
V
washed and VII
VI unwashed
Wheat rolls Rice Vegetables and Total Rice Vegetables and Total Vegetables
and
Rice porridge Chilirnix Total
IX
curry
Rice Total
VIII
curry
Rice
porridge
Vegetable Total
mix
curry
nurses at
design
present investigation comprised (see Table 1). In 4 series (I to IV)
solution
of ferrous
ascorbate
nine series, of a meal A or a
B was consumed
after
fasting overnight on four consecutive mornings in the sequence ABBA or BAAB . The meals and the ferrous ascorbate were labeled with two different radioiron isotopes (Fe and Fe) and a blood sample was drawn 2 weeks after the last serving in order to measure the iron absorption from the meal and the reference iron solution. This design was used to study the absorption of iron from wheat rolls and a composite Thai-meal in Thai and Swedish women. In one series (V) in Thai women two kinds of meals were compared . They were identical in all respects except that one was carefully minced and mixed whereas the other meal was served in the usual way. The meals were prepared from the same batches of raw materials. The two meals, called A and B, were labeled with two different radioiron isotopes and were served on four consecutive mornings, the subjects having fasted overnight, in the sequence ABBA or BAAB. Two weeks later a blood sample was drawn to determine the absorption of the two radioiron isotopes. In two series (VI and VII), aimed at studying the effect of iron contamination on iron absorption , two kinds of meals were compared as above. After the blood sample had been drawn to determine radioiron
absorption, beled
with
(amount
however,
a ferrous
radioiron
was
pe r meal
given
ascorbate in the
serve d) in the
water
solution
fasting
different
la-
state
studies
Phoaphorua
.
mclud-
Iron Total P
Phytic
mg
g
I, II III, IV,
aides and student
Siriraj Hospital in Bangkok and 25 female and six male medical students in Goteborg served as volunteer subjects. They all considered themselves healthy. Hematological evaluations and other data are given in the tables.
weight . ing
Food
and methods
Material
104 175 87 262 175
1.2 0.44 2.45 2.89 0.30
66 53 43 96 34
87
1.62
38
262 175 87 262 338 3 341 336 58 394
1.92 0.44 3.71 4.15 2.57 1.78 4.35 3.36 1.28 4.64
72 44 41 85 83 2 85 94 25 119
0 33 0 33
39 0 39 47 0 47
P
on
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ingredients and the same relative composition as the basal meals in the previous study. It has been suggested that malabsorption
AL.
ET
ABSORPTION
IRON two
mornings
to determine
the subject’s
FROM
ability
to ab-
sorb iron. The absorption of iron from the ferrous ascorbate solutions was calculated from measurements on a new blood sample drawn 2 weeks after the last oral dose. In two series (VIII and IX) the roles of the three main components of the basal diet - rice , vegetables and spices - were investigated to explain the low ab-
sorption.
In series VIII
rice flour
sign as in series
V. The chili
of a boiled
without the same chili reported study using same experimental de-
mix was identical
to that
ASIAN
DIETS
541
meals were prepared at the same time . The rice was steam-boiled for 25 mm. It was then left standing at room temperature for about half an hour and then minced in a high-speed mixer to form a homogenous paste
.
The
and then water.
vegetables
minced
A final
the vegetable
were
steam-boiled
for
in the same high-speed
mixture
mix,
was then
the chili
made
paste,
fish sauce . Radioiron was added amounts corresponding to 6CiFe Weighed amounts (300 g) of the were put into aluminum forms that a freezer. On the afternoon before num forms were removed from the
1 5 mm
mixer
of the rice
with paste,
coconut cream, and at this stage in to each subject. homogenized meal were then placed in serving, the alumifreezer and on the
used in the previously reported study, having been kept frozen at -20 C in the laboratory. In series LX the vegetable mix was studied in the same- way as the chili mix. The vegetable mix was also identical to the mix used in the previously reported study and had been kept frozen in the laboratory. The composite rice meals in study III, IV, V, VI, and VII had the same relative composition as the basal meals in the previously reported studies . Every detail in
times in tap water. The vegetables were washed in running tap water before being chopped into small pieces in the usual way. The unwashed meals were
the previous chili mix etc
prepared washed
protocol
was followed
in preparation
of
the only exceptions were the washing of the foods in study VI and VII and the homogenization in study V as described in the next section . Compared with the previous study the amount of food in each .
meal was reduced by 25 % in order to facilitate every subject could fully consume their meals.
that
morning just before serving, they for 1 5 mm in a pressure cooker.
from rice and vegetables that were not at all . The soil that was added to half of the
meals in study VII was obtained from rice fields outside Bangkok. Lumps of dry soil were placed in a porcelain mortar and finely ground. Any large particles were removed.
The
200 C. Using
of food
The wheat rolls in studies I and II were made in Sweden. A single batch of labeled rolls were baked in Sweden , and kept frozen until the day before serving. They were transported to Thailand and were kept frozen until the day before serving. The rolls were baked from unfortified white wheat flour, 60 % extraction. Each roll contained 30 g of wheat flour and had an iron content of 0.6 mg, of which 0.25 mg was added as ferrous sulphate . Two rolls were served each time . The total intake of four rolls in each subject corresponded to an intake of 3 sCi55Fe . The Thai meal, which was served to both Thai and Swedish women (study III and IV), was prepared in an identical manner for both groups of women from the same batches of raw materi-
als that were transported
deep-frozen
to Sweden
from
Thailand. The composite rice meals in the different studies were prepared in the same way, if not otherwise indicated, by weighing 50 g of carefully washed rice in an aluminum form adding 125 ml of distilled water and 2 ml of a radioiron solution. The form was covered with a lid and cooked under pressure (+0.5 kg/cm2) in a steam cooker for 25 to 30 mm. The vegetables were carefully washed and then finely chopped. Weighed amounts were put into another aluminum form together with a measured amount of a warm mixture of chili paste, fish sauce, and coconut cream. One milliliter of the radioiron solution was then added and the form was covered with a lid and cooked under pressure (+0.5 kg/cm2) in a steam cooker for 20 mm. The homogenized meals in study V were prepared at one time from the same batch of rice and the same batches of finely chopped vegetables, chili paste, etc. as
was used in the nonhomogenized were the same as used in study
meals. These batches III and IV and all these
steam-heated
In studies VI and VII the same batches of foods were used for preparing all meals. The washed meals were prepared from rice that was carefully washed 3
weighed Preparation
were
into
soil was then put into an oven for 2 hr at an analytical balance 200 mg of soil were small glass tubes corresponding to the
amount added to each meal. The soil was added to the vegetables and rice before cooking and was carefully mixed into the food with a glass rod . The chemical properties of the soil are reported later in this paper . In studies VIII and IX the meals were homogenized and prepared in exactly the same way as in the previously reported study. The vegetables and chili mix used were identical to those used in that study, having been kept
frozen in the laboratory until the present study. The amount of chili mix (paste) was smaller, however, as the Swedish subjects had difficulties taking the same amount as the Thai subjects. The only difference between the present and the earlier studies was the rice flour
that
bought
was
made
in Sweden
content of each 5 mg by adding Chemical
in
the
laboratory
in a Culatti
meal in these two ferrous sulphate
composition
mill. series before
by
The
milling
total
was adjusted cooking.
rice
iron to
of meaLs
Aliquots of the meals and/or their components were freeze-dried and then finely ground to a powder in a porcelain mortar. Weighed amounts of this powder were used for the analyses of iron (5), phosphorus (6), and phytic acid phosphorus (7). The chemical composition of the meals is given in Table 1. Serving
the meals
All meals were served under supervision in the morning, the subjects having fasted overnight. The sequence of serving the different meals or the reference solutions is given in the section on experimental design. The meals or the bread were eaten together with 200 ml of distilled water. All food and the water served were consumed.
Downloaded from https://academic.oup.com/ajcn/article-abstract/30/4/539/4650317 by guest on 09 November 2018
porridge was served with and mix as was used in the previously two radioiron isotopes and the
in the form
SOUTHEAST
542 Oral
doses
offrrrous
iron
ascorbate
A solution of 10 ml 0.01 M hydrochloric acid contaming 3 mg of iron as ferrous sulphate , 30 mg of ascorbic acid and 1 .4 Ci59Fe was used as a reference in all studies except studies V. VIII, and IX. Each
subject
was given
2 doses, taken
on two mornings. The solutions from test tubes, which were then
distilled
water
of the
were rinsed
that was also consumed
under
supervi-
staff.
Absorption
measurements
Calculations
the
absorption
of
and the reference
solution
were
surements of 59Fe and samples and standard scribed previously (1).
Fe in solutions
blood using
meals
overnight
taken directly four times with
Properties
of
ofsoil
iron
from
based
containing
1 mg of Fe/mi
was added,
0.90
the
on mea-
samples, methods
solution
mg of iron and 70% of the radioiron was found in the solution after 2 hr. When the pH was reduced to 2.4 by using 0.01 M of hydrochloric acid instead of 0.001 M, 0.11 mg of iron was dissolved from the soil. After adding the iron solution 1.05 mg of iron and 83% of the radioiron was found in the solution after 2 hr. Calculated from the change in specific activity of the radioiron, 70% had exchanged with the soil iron at both the lower pH levels whereas there was no exchange between soil iron and the added iron at neutral pH. At this pH level there was merely an adsorption of iron onto the soil.
food de-
used
study the ability of the soil used in study VII to take up iron , various amounts of dried powdered soil were put into test tubes. Ten milliliters of distilled water and then 1 ml of a freshly prepared solution containing I mg of ferric iron (as ferric chloride) in 0.001 M hydrochloric acid and a trace amount of 29FeCl were added. The tubes were shaken for 15 mm. After centrifugation at 3,000 x g for 10 mm the concentration of iron and radioiron was determined in the supernatant. The results were expressed as a percentage of the values in a test tube containing no soil. The uptake of iron and radioiron in relation to the amount of soil added is shown in Figure 1. The same uptake of iron and radioiron was obtained using 200 mg of soil when the volume of the solution was 200 ml instead of 10 ml. The pH of the aqueous solution of iron and soil after 20 and 40 mm was 8.2 and 7.1, respectively. When soil and water were mixed no iron was found in the solution. When 200 mg of soil was mixed with 200 ml of 0.001 M hydrochloric acid (pH of the solution 4.3) 0.04 mg of iron was dissolved within 2 hr. The iron content of the soil was 2.27g/l00 g of dry soil. When 1 ml of the same radioiron-labeled
Other
methods
Hemoglobin was determined as cyanomethemoglobin and hematocrits were spun in an International Microchematocrit centrifuge. Both determinations were carried out on one venous blood sample drawn into a heparin tube using a minimum of stasis.
To
IRON
Results Studies
I and
II
Comparison of the absorption of from wheat rolls and ferrous ascorbate Thai and Swedish women. The results
iron in
are given in Table 2. It is evident that the absorption of iron from wheat rolls was about the same in Thai and Swedish women. The higher average absorption from wheat observed in the Swedish women was accompanied by a higher absorption from the ferrous ascorbate solution also. This is probably attributed to differences in iron status between the subjects illustrates the value
from
a reference
in the two groups and of using the absorption
inorganic
iron
salt
as
details
see text.
UPTAKE
50
50
100
200
300
400
600
800
1000 mg
FIG.
1.
Uptake
of iron
and
radioiron
by the soil in relation
to the amount
clay
of soil added.
For
a
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sion
after fasting
AL.
ET
HALLBERG
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ABSORPTION
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+1
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544
basis
HALLBERG
for
absorb Figure
. The similar ability in the two groups is illustrated
AL.
%
to in
comparison
iron 2.
ET
20 C
0
0
0
15
Studies
III
and
IV
o0
/
10
/ / /
Comparison of the absorption of iron a composite Thai meal and from ferrous abscorbate in Thai and Swedish women. The results are given in Table 2.
0
fr om
ratio
between
and
ferrous
cantly
0 .01)
different
The
.
groups Study
the
absorption
iron
was in
food
the
from
Figure
40
60
of reference
Thai Swedish
80 (Fe504)
1#{243}0% 3
mg
Fe
FIG. 3. Iron absorption from a simple Thai meal of rice, cooked vegetables, and from ferrous ascorbate (3 mg of Fe) in Thai ish women.
composite spices and and Swed-
iron
statistically signifitwo groups (P < between the two
difference
is evident
of
20 Absorption
0 ti
Absorption Homogenized meal
3.
V
Comparison of iron absorption from a composite Thai meal served in the usual way and in homogenized form. In eight of the 10 subjects a higher absorption was obtained
from erage these was results Study
the nonhomogenized meals. On an av70% more iron was absorbed from meals. The effect of homogenization statistically significant (P < 0.01). The are
shown
in Figure
4.
VI
FIG. 4. Iron Thai meal served
absorption from in the usual way
%
a simple composite and in homogenized
form.
Comparison prepared from
The
as a graph
Absorption
of absorption washed and
percentage
between unwashed
meals foods.
was
slightly
absorption
higher washed tically
from the washed than from the unfoods. The difference was not statissignificant (P > As the iron 0.05).
content
%
0
50
higher
in
the
meals
from unwashed foods, however, of iron absorbed was greater
//
40
was
0
meals
(see
Study
VH
prepared
the amount from these
“Discussion”).
., 30 0
0
The effect on the iron absorption soil to a composite Thai meal. previous study the percentage
C
220 c36
I
o Thai subjects Swedish subjects
