Iron absorption from the whole diet in men: how effective is the regulation of iron absorption?13 L’i/’
Hallbeig,
ABSTRACT tamed
Iron absorption
a highly
men.
meals
was
labeled
added
in amounts
Heme
iron
cabby
labeled
including
labeled with
total
to cover
iron
60
concentration will
occur
by
that
in normal
to iron
ji.g/L iron
subjects
there
is no risk
indicated
serum
fernitin
an effective
of developing
weight
was
the
a high
iron
bioavailability.
gest that translation stored iromi should high
serumii should
heme-
amid
status
and women These
new
concentrations.
be
iron
identical
There
causes
absorption
different.
but
Aiim J Cli,,
than
Nuir
relations
and
WORDS
iron,
men,
Iron
iron
absorption.
overload,
iron.
ferritin.
diet.
iron
iron
tracer
iron
of both
sorption
of
to
between
hemiie-
studies.
The
iron
lated ( I I
an
INTRODUCTION
between
tions
and
of iron
iron
absorption
deficiency
effective
is
relation
( 1-9).
and
the
less
regulation
in states
of
iron
for example. obvious
AI?l
J (liii
deficiency
in women conclusion Niar
is
l997:66:347-56.
that
iron
iron
iron
fernitin is absorbed
stores
are
absorption
to
in otherwise absorption can
normal increase
and
and
More
when of
deficiency and iron overload It is well known that iron
serum
that
iron
deficiency
way that
was
I
2
How iron
in USA.
U
American
between
two
studies
total
only
an extrinsic
the
same
specific
by
studies
between
in total
iron
measured
using
relations
observed
in other women.
in
aniounts
of’
requirements
menstrual
calcu-
iron
losses
total
the
fiur
diets
5 or of
for amounts
Medicine.
with
different
10 d. Linear iron absorbed
Department
Annedalsklinikerna.
Swedish
and reprint
Gioehorg
Medical
iron
relations and log
of Clinical
Sahlgrcnski
GOteborg
Swedish
Council
and
997/88L
I l3:3).
requests
to L I-lallberg. Annedalsklinikerna.
5-4 1 3 45.
Jamiuarv
Accepted
fr
Nutri-
t niversimy
for
Council Forestry
Depanimetit
(project and
of Climiical
Sahlgrenska
B94.
Agriculture Nutri-
University
Sweden.
2 I . 1997.
publication
Nutrition
Research
the
University.
Received
Clinical
in women served
Sweden.
by
(50.0120/95
Hospital.
fir
and
in
individual
and
of Internal
Goteborg.
Supported
tioii.
Socict
and
University.
Address
is common,
997
first
absorption
validated
weights
were
Gtehorg
Research
teenagers in most populations. The the regulation of dietary iron abPrinted
the
by adding
tracer
agreement
studies
two
l9X-0472l-l9A
subjects? severalfild
was
absorbed
Froni the Institute
Hospital.
in a state
prevent
detertiiine
to achieve
radioiron
good
body
found
tioii.
concentrareplete.
regulation
).
were
inverse
to
In the
nonheme-iron
method
iron
from
In these
is an
periods.
on the
the whole diet ( I 0). The labeling of’ all nonheme
measured
in amounts
and
hioavailahilities
there
was
differdif-
diet.
in all meals.
inorganic
there
dietary
bioavailahility
iron stores in some unknown Several studies have shown
whole
balance
studies
of
because balance
of all nonheme iron in all daily meals served over several days ( 10. 1 1 ). In these two previous studies, heme-iron absorption from the same meals was calculated from the ab-
stores.
It is well established that influence iron absorption.
long
for
a method
absorption
inorganic
nonheme iron
requires
been
studies
activity
1997:66:347-56.
heme
serum
the
developed
all heme
has
direct
no
to
of iron
diet,
the whole diet The chemical
of dietary iron absorbed from is based on a separate uniform
whom
KEY
and
suitable
from
we
nonheme-iron
sug-
increased
control
their
iron
into amounts of in subjects with
effective
was
amount method
with
strongly
absorption
in the
been
he
(8).
development is
have
to
in rekoion
iron absorption is measured as the intake and fecal loss. is technically is not
method
Recently.
same body
diets
inaccurate.
of iron
Similar both of
to prevent
of iron absorption from method has been available.
rather
considered
recently
needed
There
ficult.
he
regulation
examined
than
extensively.
which dietary
this
was
iron
may
ofthis
absorption
more
method. with ence between
Thus.
overload
At the kilogram
observations
other
considered.
nonheme-iron
were
served
stores
less
regulation suitable
ho
suggest
is firtified. in women.
of serum ferritin concentration be made with caution and that
femtin
stores
in men
same
the
ferritin
thus
control of absorption. the absorption per
concentration
suffi-
of iron
findings
by iron absorption from the diet even if the diet findings were made previously in two studies which
serum
just
of iron
diet
is not sufficiently effective with high physiologic iron
diet
efficacy
and
when
studied
the
when
The
requirements
Regulation
this
at a serum
even
adequate.
overload.
good
ferritin
a bevel
accumulation The
iron
of
serum At
to that
absorption.
a
concentration
absorption.
implying
no further
dietary
was
with
decreased
requirements.
generally
hiosyntheti-
There and
in all tracer
in all meals.
hemoglobin
In subjects
losses,
iron
radioiron
tracer.
absorption
basal
using
sorption to meet iron requirements to prevent iron deficiency in those
con-
f’or 5 d in
activity
absorption
60 pg/L. no relation
concentration.
cient
by
which
Nonheme
specific
radioiron
between
diet.
measured
inorganic
uniform
similarly
whole
was
donors.
extrinsic.
another
serum ferritin up to > 60 p.g/L there was
the
March
26.
1997.
347
Downloaded from www.ajcn.org by guest on July 13, 2011
relation
ferritin
an
Gra??zatkot’.ski
of iron,
12 blood
with
to ensure
was
from
firm
hioavailahle
31 healthy
inverse
Hiilt#{233},i, (111(1 Elizabet
Leiza
348
HALLBERG
serum
fernitin.
The
significantly that
the
scale
slopes
different. lines
the
low
to estimated
this
basal
serum
four
regression
interest
was
to a point
absorption
estimated
that
the
special
converged
corresponding
Fe. The
of
Of
iron
obtained losses
on
range
from
suggesting
that
iron
the
did body,
the
are
mg
not
suggesting
in men
Technology
at the
informed
that
that
the
suitable We took
because
than
in
high
regular
absorption
me
relation
in men,
and
men
blood
iron
absorption
both
groups
with
iron
over
small
several
absorption
including
both
We
and
serum
also
served
an
and
the
serum
and iron
compared
fernitin
days
healthy
or negligible
donors. were
diet
to measure
men, stores
the
in men
identical
diet
to examfernitin
women
with
of
of
iron
conditions.
status
under
realistic
about nations.
because
whom
bio-
iron status and to examine absorption from the whole diet
AND
Forty
men
the and
rate,
from
the staff the
The
of the
subjects’
TABLE I Characteristics
and
student
School
of
body
of the Sahlgrenska
Dentistry.
the
the
reasons The
were
Age (y) Body weight
(kg)
Height(cm)
(Pm
for
exclusion
and
3 1 men
blood
donors.
The
characteristics
laboratory
screening
pacity,
total
serum
serum
Blood
by
(n
(22-59)
=
26.3
±
7.67
(20-55)
34.3
±
13.4
75.5
±
9.l7
(63-102)
79.8
±
9.98 (66.6-98.1)
Hematocrit
0.47
±
0.02
0.46
± 0.02
(0.43-0.49)
153 ± 7.0(140-168)
results aged
informed
of the 20-59
examiy,
of the
12 of
subjects
of the participants
Radioisotope Medical
Committee Faculty
assessment ferritin,
serum
I 2)
of the
of hemoglobin
total-iron-binding
ca-
high-density-lipoprotein insulin.
cholesterol, serum
serum bilirubin,
All subjects
183±6.5(174-196) ±
transferrmn
the
included serum
donors
2.43
of an
erythrocyte were
of the
low-density-lipoprotein serum glucose. serum
2.6(2()-31.8)
elevated
examinations
cholesterol,
±
developed signs
of subjects
hematocrit,
I80±5.5(l70-188)
the
he to a
of serum results from they
subjects
was
23.4 (gIL)
nine
of the
of a mod-
carbohydrate-deficient
These sample
concentration,
19)
an
final
BMI (kg/ni2) Hemoglobin
high
assessment
cholesterol, tniacylglycerols,
Chalmers
Nondonors
and
because
of laboratory
inflammation,
and by the Ethical Committee University of Goteborg.
METHODS
Hospital,
or
to select
one because he admitted
three
because
involved
a history
of an infection
two
and the results of the screening are given in Table 1. The project was approved
Subjects
University
work
including
were
of them
screening
and high concentrations because of abnormal
because
and
concentrations.
Laboratory SUBJECTS
one
study.
infection
(CDT)
form of iron. Attempts were also made to examine the of different methods to calculate heme-iron absorption
from various indicators relation between heme-iron
the
sedimentation
between
a highly
extensive
of alcohol,
Donor
They
number
a laboratory history.
of alcohol one
tests,
before
ongoing
iron-replete
relation
and
iron
as a result
a limited
and
Blood
(,i
=
29.4
±
10.8
77.2
±
9.6(63-102)
(20-59)
I8l ±6.1(170-196)
2.7(20.9-28.7 (0.43-0.5
1)
151 ± 9.9(133-169)
23.7
±
0.47
± 0.02
2.6 (20-31.8) (0.43-0.51)
152 ± 8.2 (133-169)
I9.9 33
±
4.4 (12.5-29.5)
±
5.4 ( 12.5-29) 9.2 (20.5-52.5)
20.4
±
3.7 ( 15-29.5) 5.8 (24-45.5)
±
34
33.4
±
7.2 (20.5-52.5)
Serum ferritin (j.tgIL) Erythrocyte sedimentation rate (mm/h) CDT (U/L) Serum cholesterol (mmol/L) Serum triacylglycerol (mmolfL) Serum LDL cholesterol (mmolfL) Serumii HDL cholesterol (mmol/L) Serum ALAT (MkatIL)
91.0 2.9
±
36.9
36.8
±
15.82
70.0
± 40.3
±
1.9(1-9)
±
4.1 (1.5-16)
15.9
± 4.0(9.6-23.3)
l6.4
± 4.7
(I 1.7-27.7)
16.0
± 4.2(9.6-27.7)
4.81 1.06 3.02 1.38 0.40
±
0.95
(3.1-7.1)
4.75
±
0.67
(0.67-3.1)
4.78
±
±
0.44
(0.49-1.9)
1.20
±
0.67
(0.67-3.1
1.10
±
0.54(0.49-3.1)
±
I.0(l.3-5.6)
3.00
+
0.60(2-3.8)
3.Ol
±
0.84(1.3-5.6)
±
0.23
( I . I-I .9) 0.1 1 (0.27-0.69)
1.25
±
0.20
±
0.44
±
0.14 (0.24-0.69)
0.41
±
Serum
0.38
±
0.13
0.35
±
0.07
0.37
± 0.1 1 (0.26-0.85)
2.65
± 0.49(l.55-4.l5)
Seruni
iron
(niol/L)
Transferrin
20.6
saturation
ASAT
(‘Ye)
(kat/L)
±
(44-176)
4.3
(0.27-4)85)
Serum
ALP
(katIL)
2.75
± 0.44(2-4.15)
Seruni Serum Serum
bilirubin (j.tmoIIL) y-glutamyltransferase insulin (mUlL)
13.5 0.33 9.22
±
5.8 (6.3-33.5)
16.8
±
±
0.15
0.37
± 0.13
±
2.55(3.5-26.3)
7.18
±
4.l4
±
0.76
4.29
±
a-glucose ‘
(MkatJL)
(mmol/L)
.t ± SD: range
amiiinotransf erase. 2 Significantly
in parentheses. different
from
CDT.
carbohydrate
nondonors.
P
Note that (70 jtg/L)
value and
in this
concentrations
jtgfL).
Estimates
351
a “tail”
ferritin
0.0001)
(P
absorb the same same iron status.
FIGURE serum
the same y
lines for absorption
the
t test).
This
amounts
of
of the
In studies status
method
of dietary on the
used
iron
lines was
means
iron
that
from
the
agreement
was
weight
iron
to be able
absorption
to relate
the
in validating iron statuses
and
iron
absorption
not
a certain period to individual
the method and to study on iron absorption and
the iron
balance. The
finding
(0.98
mg)
basal
iron
served iron
was
the
not
significantly
requirement
as blood balance.
that
mean
( 1 .06 mg)
donors, implies
total
and that
the
who
amount
of
different
from
in those
19 men
may
present
iron
absorbed
the
calculated
be considered method
not
significantly
who
had
to measure
the
total amount of iron absorbed from the diet over several days is valid. This result is consistent with observations in the two previous studies ( 10. 1 1 ) in menstruating women when the same method was used to measure iron absorption. Good
of
extrinsic
labeling
Validity
of selection selection
normal
ing
different
nor
were
the
the
(eg,
the
total
daily
amount
are
thus
the
three
separate
present method diet over several
of all meals
to the
same
to
subjects
same
smoking
with
was greatly
range
and
absorption, the
distributions uration
study
made
were
iron using
to obtain
varying
as seen
iron
activity.
alcohol
within
who
had
normal
to
blood
seen
in Table
and
limits
influence
of serum se is known
donated
concentrations
There-
conducted to or lifestyle
known
As
and
of
extend-
women.
were disorder
abuse)
excluded.
a sample
statuses.
in healthy
examinations have had any
those were
of hemoglobin values
illus-
of subjects
and laboratory who might
iron
studies measure days by
specific
iron-status indexes, especially the concentration ritin. Because increased erythropoiesis per before
of iron
individual daily iron requirements. from individual measurements of basal iron losses calculated from
whole
men
to about
factor
the
of
healthy
fore, clinical exclude those
mo
to be in
validity from
increase not
between
(1 1 ). There
the
The
between
just to a single meal but to the whole diet over of time. It is then possible to relate the absorption iron requirements effects of different
daily
found
absorption
absorbed
relation
it is advantageous
total
were
absorbed from the diet and The latter was calculated menstrual iron losses and body
to measure
slopes
(1 test).
relations were very
DISCUSSION Validity
The
(.tgIL)
total iron absorbed in 20 men with a log I .9 ,,tg/L and in 2 1 women who were served study ( I I ). The regression line fir the men was 0.46)andforthewomenwasv = 0.152 0.078x
in another
0.687).
,.2
ferritin
(P
Log
the iron
70 p.g/L were included in the comparrange of serum ferritin values was used in
v intercepts
and women diet at the
when
relation
men and women. As shown in Figure 3. the regression between log serum ferritin and total iron similar in men and were not significantly
value
Therefore,
the
ferritin,
0
ferritin
femtin
and
0. 0 Cl)
with serum
,.Lg/L)
0
.0
stores. In the sample of 2 1 women used in the comparison men the highest serum ferritin value was 70 gfL (log I .85
C
the Be-
C
discussed high
E
absorption
are compared and
a)
Total
recalculated to make directly comparable.
absorption
0)
Therefore. in women
in the
women
0
.0
ferto
in the 2 1 , the
transferrin not
sat-
significantly
different between blood donors and nondonors. It is also of interest that mean percentage nonheme-iron absorption values were not significantly different (P > 0. 1 ) between the blood donors and the sample of women served in the comparison of men and women
the same Thus,
( 1 1 ).
diet and used in the present
Downloaded from www.ajcn.org by guest on July 13, 2011
“tail”
men
#{149}0
than
previous
veal.
cause men and women differ in body weight, was calculated per kilogram body weight.
‘a)
percent-
higher
absorption
used
of
used in the measurefor
previously. only
refer-
prediction
I 2%
±
realistic
of log
values
28.4
used
use
therefore absorption
gave
were
the equation
same
absorption
a better
=
AL
and log direct
under
the
0.72) and was no direct heme-iron (r
comparison
the
based
from
present
men
nonheme-iron
in 23 subjects
equation,
absorption
derived
and
made
(see
made.
heme-iron
were
new
absorption
heme-iron absorption In the present studies
heme-
meals
dose
age
between only 0.36.
ET
REGULATION analyses
of relations
status and
in men nondonors
mentioned was
relation normal
iron
reexamination of serum
lation
coefficient
The
ferritin
to 250
of only
iron
serum
studies
between ferritin
( 1-9).
iron
measure-
In a study
on the
clinical data for 50 subjects, was 0.60 (4). This material, both iron deficiency values up to 5000 data
showed
p.g/L
of
evidence
that
produced
of
the
amount
and iron j.gfL. A
limiting
the
a squared
that
of
high
corre-
serum
stored
amounts
ferritin
iron:
bow
indicate
is a
amounts
states
of
evidence
iron
higher amounts than women. Morethe content of nonheme iron in the ferritin has also been shown (4). On
a high
alcohol
intake.
of a relation
between
ferritin concentrations was ing the stores by quantitative
obtained in four phlebotomies
ing these results the squared serum ferritin concentration stores was only in serum ferritin
=0.5, was
stores
and
studies (22-25).
indicating that only related to variations
iron. All these data indicate variation in serum ferritin was
the
ferritin in Figure range of
70 pg/L
>
by measurBy pool-
tail.
the
was
reference
relation
also
between
examined
dose
a straight dietary iron
the
measure
r
of was The
0.832. This seen in iron-
=
range
a good
of
line relation absorption.
4
is not
by
instead
as an independent
coefficient was high. serum ferritin in the
that
and
the
status
measure
of their
iron
stores.
ferritin
was
amounts
two
considerable,
of stored
clinical an
36%
study
iron
stores
60-70 to meet
further
accumulation by absorption serum ferritin this
to other men
measured
by
liver
range
was
phlebotomies
>
(26).
ferritin
correlation
that
In
concentration
in serum no
in body
(>
60-70
from
seen
and
in normal I .8 j.g/L
serum subjects (serum
was within the range which means that a iron
than
g/L)
the diet
factors
higher
iron
ferritin.
stores
will
not
of iron from the diet. Consequently. values observed in the iron-replete
derived
unknown
with
men
to predict
of serum
in
healthy
of iron
critical stores
variation
serum ferritin and variation in serum
it difficult
iron absorption iron requirements.
/.Lg/L).
basal
place
iron
making
concentrations
(24). in the present study ferritin concentration
>
high
between that the
of the variation
in
ferritin concentration It was obvious with a log serum femtin
from the
for only
needed
in turn
iron
studies
earlier
between
high
serum
correlation coefficient between and amounts of mobilizable
from
shown whole
correlation suggests
above iron
of
iron
of serum As the
men
cause
and
(see normal
were
not
take the men
due
to the
but were
probably
related
This
suggests
that
below). serum
ferritin
in
concentrations.
the iron
50% of the variation in amounts of stored
that a considerable part of the not related to the size of the iron
stores. In our previous studies seen between total daily serum with
ferritin. serum
The
values
(Figure
1 ). The
present food
data iron
in the
in the present
70
relating
tg/L. no
normal,
sample in the vey
the
frequency
reference
dose ferritin
seen
absorption (data
of serum
>
ferritin
(NHANES
ipate
in the
and
laboratory we
II) that
in
the
9 of the
present
study
United 40
men
were
examinations.
tried
to
exclude
States
instead
in the
excluded In the
those
after 3 1 men
men
who
careful selected might
C 0
of
>,
a 0
who Note
‘D
a
present
0
I-.
of men Sur-
It should
invited
a
here).
in women, 70 p.gfL.
(12).
originally
0 Cl)
.0
thus in the
not given
studies values
‘O 0 .0
noted
men
also
a) E
serum
was
of men was the same as in the extensive sample second National Health and Nutrition Examination
remembered
study
was
‘O
in men
with
relation
tail
to log serum
distribution
studies
men
iron-replete
A similar
Such a tail was not seen in the previous on the other hand had no serum ferritin that
In
however,
in these graph.
absorption
significant relations were of iron absorbed and log
seen
j.g/L,
results
by
was
values 70
>
a tail
formed
same
ferritin
femtin
in women, amounts
be
to particclinical for have
the had Absorption
elevated concentrations smoking, liver disease, ing the month preceding
of serum ferritin due to alcohol intake, mild diabetes, and mild infections durthe study. Therefore, the probability is
sorption
bow
due
0.606
that
influencing
the
tail serum
was ferritin.
to
any
known
pathologic
factor
FIGURE
4. Relation from
(p.2
requirements.
=
reference 0.832).
from
between doses
The
total
reference dietary
doses iron
(%)
absorbed
The regression line was y horizontal line indicates mean (x.
(v)
and 0.079x
basal
ab-
iron
Downloaded from www.ajcn.org by guest on July 13, 2011
with
Direct
status. over
replete
the
absorption absorption
accounted
hand it is also well-known that increased and often serum ferritin values are seen in inflammatory and disorders, in liver disease, in starvation, and in
association
the
squared finding
In suggests
deficiency,
examine
iron
iron seen
353
In a critical review of the relation amounts of stored iron it was shown
0.21.
overload, and men have over, a relation between bOne marrow and serum the other very high infectious
on
with ferritin
published
indicator
indicate
patients serum
of the
balance
good
dietary
concentration a relation
based
which used coefficient
ABSORPTION To further
iron
donors
log absorption and log serum ferritin in 47 the squared correlation coefficient was 0.67
included who had
range
and blood
stores
in several
(7). In another study, the squared correlation however, overload
absorption
IRON
using
Introduction
status,
observed
between subjects
iron
to combine
sample.
to iron
in the
and
ments,
present
in relation
absorption
dietary
it was justified
in the
Absorption As
between
we think
OF
HALLBERG
354 iron
stores
cannot
concentrations. known fact with
be estimated
This that high
a marked
accurately
from
conclusion does not serum ferritin values
pathologic
iron
amounts of stored iron from must be made with caution.
serum
contradict are seen
overload.
Thus,
concentrations
of serum
AL
5). This
ferritin
the wellin subjects
estimation
ET
of ferritin
effective.
that
a high
stores
in relation
status
between
men
observed
and
no
than
men
ments.
No good
data
that
women adaptation
are available
absorb more dietary iron to higher iron requireto support
However,
it is evident
from
the simple
that
men
and
women
absorb
about
the
same
diet
from
ologicably,
when
it is not
their
same
status
that
speculation.
comparison the
iron
astonishing
such
in Figure amount
is the
same.
the regulatory
3
of
iron
obvious
in dietary
in men iron
related
to
in
iron
established
of iron
stores.
(23. 27) conducted
content of was 280-92()
weight
55-453
mg.
reported
women
but
tions
in women
more
efficient
requirements.
are
iron
thus
status.
and
based
blood
than in men in men, with
mobilizable mg. The
the
in that
is
27-32). 79 subjects.
601
nig; average
excluded):
the mean
of iron
regulation
not
There The
of iron
The
higher
serum
absence compatible
in Australia reported
of
an is
in Australian of iron
in the
serum
Introduction,
reasons why iron stores in women are smaller than in men. Women are usually their iron balance varies during the fertile of menstruation and pregnancy.
by
higher
iron
meat in
on
serum
the
present
The
controlled.
the higher meat ferritin concen-
it is well-known
serum
ferritin
down-regulation partly study
ferritin
iron
of
that serum
iron
however,
absorption
has
not
of the lack of suitable ( 1 1 ) it was observed very
concentrations.
from whole low values
Four
bioavaibahibity
that
increases;
of iron because in women
that the total amounts of iron absorbed served over several days. decreased to different
explained
their
men.
when
been addressed directly. methods. In a previous
edly
been
well
in
concentra-
finding
also
signifi-
absorption
decreases of this
was
ferritin
have
it unlikely the higher
those
analysis.
concentrations
to meet the
absorption
intake
effect
with
make explains
mentioned
well
in order
thus
intake
As
Meat
ferritin
is
tration
absorption
found.
may
than
a careful
serum
The men
Despite
was
in men
populations,
higher
high
absorption
heme-iron
increasing
± I SD was
than
much
(33).
men.
iron
the efficacy
the mean value in
in
Australian
were
populations
findings
aver-
measurements.
(22-25, a total
iron was corresponding
that
with a total 1 8 subjects, was 254 with an iron store of 1054 mg and
of 1 1 1 kg were
There are obvious usually considerably smaller in size and age period because
on
studies
asymptomatic
with
requirements. study
differences
women
is also
a hypothesis
to an accumulation the strong
values
explanation
mechanisms
and
in several
women, from only two studies mg (results from one woman a body
often men
lead
by bypassing
ferritin
Regulation well
in women 10 studies
average ± I SD
The
between
might
absorption
do not support
were
studied.
20
25
diets
diets, with mark-
with
Iron
absorption
45
40
The
relative
role of heme-iron
absorption
on total
iron
absorption The
absorption
by iron
of both
status
but
Our findings kinds of iron
heme
the effect
and
nonheme
is more
marked
iron
is influenced
for nonheme
35
iron.
showed that the fractional absorption of the two was the same (=40%) in a state of iron depletion
corresponding to a serum ferritin concentration (Figure 2). At higher serum ferritin concentrations in iron absorption was more marked for nonheme
of 10 p.g/L the decrease iron. Our
findings are thus almost identical to those reported al (7); however. our data were based on the average
by Lynch absorption
from
the
whole
findings
are
greater subjects
part than
both
kinds
amount iron
mixed
of the total in iron-deficient of iron
of heme of
iron
requirements.
are
iron
in the present
amount
diet
over
5 d. The
important-heme-iron absorption subjects.
influenced
absorbed,
study
implications
absorption
by despite
( I .8 mg).
needed to he From a common
was
of
When we directly heme iron, there
absorption
with
0
0 Cl)
.0
a
C 0
et
form
25
E
of these may
30
0.
0
a
I
20
iron in iron-replete It is also evident that
iron
status
and
the high
intake
less
half
than
absorbed to Western-type
half the amount of heme iron than in the present values for absorption need to be correspondingly and
C
cover diet
that
the
of heme (45%)
15
the
basal iron with about 10
diet ( I .8 mg), reduced.
compared the absorption from nonheme was a rather steep decrease in heme-iron decreasing nonheme-iron absorption (Figure
5
10
15
Nonheme-iron FIGURE iron.
The
5.
Relation
regression
line
between was
v
absorption the
=
30
12
absorption +
19.71
X
(%) of
henie
logx
(r
and =
nonheme
0.63l.
Downloaded from www.ajcn.org by guest on July 13, 2011
amount
lower were
women.
differences
body size. It was also age
and
absorption
of heme-iron
findings
large
tWo
associated
ferritin
Physi-
of
in other
present
are the same
intake men
serum
cantly
suggested as a physiologic
these
absorption.
women
It has been
meat
In a study
to iron
the control
Thus.
in normal
median Absorption
that
means
very
REGULATION from
all
ments. stores.
diets
thus This
ability.
decreased
It was
ments
the
estimated
decrease
agrees
with
These
results
conclusion will not logic
below
in
the
that
iron
in women
in both
in
in the
women
iron
low
iron
in the
thus
by ab( I I).
the
study
same
stongly
normal iron-replete body above certain
the
subjects. iron upper physio-
limits.
mechanism
that
body.
will
prevent
In epidemiologic
ferritin
values
33).
In
observations there is an
accumulation
studies
peak
in
a carefully
the
it has been
third
designed
to
and studies that effective control
of excess
iron
observed
that
fourth
decade
in
iron-fortification
was given
improve
bioavailability
dietary
the
iron
in iron-replete man, 10 mg
replete main
meals
noted with
500
d with
lating
example
iron
of the
absorption
(37) States
The
capacity
is from
of
NHANES
significantly the
serum
in serum
same
was
no
mechanisms
II. there
was
ferritin
the
mechanism
necropsy
studies
increase
in was in I 8
factors
a shift
skewness
States.
present
finding iron
in only
related
to age
concentration higher
that
absorption
are
less
risk
subjects.
for
Because
iron
iron
understanding understanding illustrated tive, high
iron
overload
cannot
there and
valid
observed or moderate
to detect in iron-replete results ( 1 1 ). In addition, will
be regulated
nonheme iron
in the same
iron. would
in otherwise
be actively
Thus. there constitute a
normal
secreted
from
that
for
of our environment humans (4 1 ) make
survival.
both
developed
effective
control
deficiency
and
overload.
iron
control
of
iron
in
in iron-replete
and the
of the regulation of iron absorption iron metabolism and iron balance. This in a recent review (40). From a teleobogic
the high iron content iron intake by early
is an that
the same from is that studies of
differences in bioavailability or in subjects with small
of fortification
replete
confirmed
that
absorption is about iron bioavailability
absorption
marked subjects
special
humans
and
mechanisms The
absorption
is
body.
an
is key to was well perspec-
and the assumed it reasonable to animals
must
to prevent
present
iron-
finding
have
both
iron
of an effec-
compatible
with
this
the
distribu-
serum
this that
ferritin
and
on a statistical
elevated morbidity
(based
there was is important
serum ferritin in coronary
in that
study
was
with
a high
indirect must
A,
subjects
for
that
the
mod-
(> 200 p.gfL) in men (39). The
amount
of stored
iron
is a risk for coronary such a relation must
artery disease. However, the causality of be seriously questioned on the basis of the
present
that
conclusion: should
not
moderately be translated
elevated into
concentrations higher
iron
F. Worwood
patients
with
of stores.
M.
iron
Ferritimi
deficiency
in the
and
seruni
of
iron
overload.
CA.
Serum
normal
Br Med
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1972:4:206-8.
JD, Lipschitz of
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Z Naturtorsch
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be
an increase
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the there
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of serum values.
hypothesis
all
conclusion.
a recent
ferritin
I . Jacobs
absorption.
ferritin
is an
and
that
conclusion
U
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age
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study
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30 y, there
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not
men
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men
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In a recent sulfate was
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effective
Finnish
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Another
after iron
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ftr
iron daily whereas
this
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( I 2,
in which
(36).
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by other Another
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factors
diet.
support
IRON The
require-
present
served
men
There are several
in
require-
be attained 4-500 mg
men
women
and
that in otherwise accumulate in the
with might be
absorption
findings
basal
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