Iron fortification of flour with a complex ferric ...

Iron fortification orthophosphate1 LeifHallberg,

of flour

with

a complex

3

Lena

Rossander-Huith#{233}n,

ABSTRACT

prompted the two

The

us to search requirements

bioavailability

(P04)6

and

Elisabeth

unexpectedly

study

low

Systematic

6H2O, a well-defined

of compatibility,

complex

ferric

cover energy generations

implies

that

requirements than ago. The nutrient

is therefore

a common cially

in infants,

age. The

fortification,

less food

complex

is needed

was required requirements,

Iron

ferric

to

just a few however,

and

health

is considered with

deficiency

is still

countries,

women

of Fe fortification

public

in countries

used.

in industrialized

children,

efficacy

important

flour

widely

problem

espe-

of child-bearing

programs

is thus

an

problem.

the ideal

vehicle

cereal-based

diets

for Fe fortification because

it is usually

milled in a few places in a country and is widely consumed, irrespective of age, sex, and socioeconomic status. Moreover, there is no risk of overconsumption (1-3). Certain technical difficulties are encountered by adding Fe to flour,

mainly

rebated

to the

ofthe

Fe compounds

used.

Ferrous

dized

to form

ferric

oxides.

flour

is usually

colored

ical reactions fur compounds

blue-black reactions

between

10% and

may thus or with

take place. polyphenobs

colors. during

.4?)? J C/in Nuir

Fe may storage

1989;50:

129-35.

and

bioavailability

(CFOP),

Fe3H8(NH4)-

orthophosphate,

humans,

bioavailability,

methodology

are the same today, which means that more nutrients need to be absorbed per unit energy. Fortification of suitable foods with nutrients consumed in critically bow amounts

powder

This compound was labeled with 59Fe, and the native 55FeC13 . The ratio of absorbed 59Fe to absorbed 55Fe is a direct

such

lifestyle

solubility,

orthophosphate

iron

of flour that fulfill of flour) and good

compound.

Introduction present

of elemental

with ofCFOP that joins the nonheme Fe poo1 and that is made potentially The relative bioavailability of CFOP varied from 30% to 60% when served with different meals. The CFOP meets practical requirements flour well, with regard to both compatibility and bioavailabibity in Nutr 1989;50: 129-3S.

Iron

radioiron

in humans

suitable for Fe fortification (due to high water content

also

offlour, Printed

chemical

Fe salts The

may

be oxi-

content

15% and various

of

chem-

Fe may react with subin the flour, causing

catalyze

lipid

causing

negative

in USA.

oxidation

such

as ferrous

fore be used marate

make

the

Society

flour

organobepticalby

that Fe induces negative effects on the related to the fact that some Fe may be storage. Easily soluble Fe compounds sulfate

to fortify

is lower

or ferrous

flour.

at neutral

gluconate

The pH

can

solubility

but

increases

not

there-

of ferrous

fu-

markedly

in

the presence ofascorbate and has also been shown to induce rancidity in flour (4) and discoloration during storage or baking. To avoid undesirable changes ofthe flour during storage, only Fe compounds insoluble in water have been used as fortificants. For this reason elemental Fe powders are the most commonly used Fe preparations today for fortifying flour and cereal products. Knowledge about the bioavaibability of elemental Fe powders in humans is very limited. To measure the bioII, University Research

ofG#{246}teborg, Go-

Council(project

B88-

l9X-04721-13B), the Swedish Council for Forestry and Agricultural Research (864/86 3 1:2), and the Swedish Agency for Research Cooperation with Developing Countries (9.49/SAREC, Ans 85/46:2). 3 Address reprint request to L Hallberg, University ofGOteborg, Department of Medicine II, Sahlgrenska sjukhuset, 5-413 45 GOteborg,

Sweden. ReceivedApril 11, 1988. Accepted for publication August

effects,

© 1989 American

which

I From the Department ofMedicine teborg, Sweden. 2 Supported by the Swedish Medical

properties

water

as rancidity,

unacceptable. The probability flour is ofcourse dissolved during

for Clinical

Nutrition

16, 1988.

129

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KEY WORDS

bioavaibability

studies

of a microcrystalline

Fe in meals was labeled measure ofthe fraction available for absorption. labeled wheat rolls were of an Fe fortificant for humans. Am J Clin

meals,

Gramatkovski

for other Fe compounds of insolubility in water

in humans.

led to this

Our

ferric

HALLBERG

130 availability isotopes,

one

of the Fe it is necessary to label the Fe powder

to use two and another

radioiron to label

the nonheme Fe pool ofthe meal. Otherwise it is impossible to know if a measured absorption of the added labeled Fe is determined mainly by properties of the meal in which

jects

the

studied,

studies interpret

Fe is included,

by the

or by properties

on singly labeled but suggest that

Fe status

of the

of the

Fe powder.

sub-

Early

Fe powders are thus difficult the bioavailability was poor

to (5-

6). A clinical trial ofvery high levels offerrum reductum (60 mg/lOO g flour) for 6 mo, corresponding to 80 mg Fe/d, during which the hemoglobin response was measured also indicated that the quality of reduced Fe used was poorly absorbed (7). The efficacy of elemental Fe powders

for the prevention

ofFe

deficiency

was

thus

seri-

ously

cation to increase in animals strongly

these fine-particle was much higher ally,

studies

on

solubility suggested

preparations ofelemental than those previously used carbonyl

with very small showed the same sulfate

and bioavailability. Studies that the bioavailability of

Fe

(an

Fe powders (8, 9). Actu-

elemental

Fe

tests

in Fe-deficient

rats

when the Fe was baked in bread (10). The bioavailability in man ofthe presently used, commercially available elemental Fe powders with finer partides

(mainly

carbonyl

Fe preparations

and

Fe is potentially

absorbable

from

a diet

as a whole.

In the same study it was also found that the dissolution properties of another widely used elemental Fe powder (Glidden A 1 3 1 , Glidden-Durkee, Johnston, PA) was not better than for the carbonyl Fe preparation studied, strongly

indicating

that

its bioavailability

was

about

the

same. Comparative studies in rats actually showed that carbonyl Fe had the highest bioavailability of the main commercially available Fe powders (10). The fact that fortification Fe constitutes a fairly large proportion ofthe total Fe intake in several countries (2040%) led to the conclusions in our previous study ( 1 1) that the rationale of using elemental Fe powders for the fortification

of foods

for

human

consumption

handle

study

was

made

of factors

influencing

the

bioavailability

and the physicochemical properties of such Fe phosphate compounds. The aim was to find an Fe compound that was insoluble in water, and thus highly compatible with flour, and at the same time had a good and reproducibbe bioavaibability in humans. Work in cooperation with the Department of Inorganic Chemistry at Chalmers School ofTechnobogy, G#{246}teborg,and with Eka Nobel AB, Bohus, Sweden, resulted in the development of a microcrystalline complex ferric orthophosphate (CFOP), Fe3H8NH4(P04)6 . 6H20 (Chemical Abstract Service #CAS 38685-32-4) with very promising chemical and biological properties. This paper describes studies of this compound in humans. One part of the study is devoted to a comparison of the relative bioavaibabibity of Fe from two types of femc

orthophosphate

in bread

and

served

and

with

bioavaibability ofFe from was used as an Fe fortificant

the present

the same

kind

the

was and

CFOP of flour

CFOP

baked

of meals. studied served

The

when it in bread

at different meals or given in a cereal. A short report is also given on studies made to examine the effect of this Fe compound on the properties ofthe flour.

electrolytic

Fe powder) was unknown till recently. A study of a carbonyl Fe preparation labeled with 55Fe by neutron irradiation found its bioavailability in humans to be very bow ( I 1). It can be estimated that, on average, only 10-15% ofthis

and

One starting point for a search for a better Fe fortificant was an earlier observation in our laboratory (unpublished, 1978) that the potentially absorbable fraction of Fe from certain preparations of ferric orthophosphate may amount to 30-40% in humans. Because this figure was clearly higher than for carbonyl Fe, a systematic

plain

powder

particles) have been published that efficacy for carbonyl Fe as for ferrous

in hemoglobin-repletion

available because they are difficult to produce safely due to their pyrophoric property.

must

be

reconsidered and that it was important to search for other Fe compounds with known, higher, and less variable bioavaibability in man. Two studies in humans ( 1 2, 1 3) suggested that it is theoretically possible to make hydrogen-reduced Fe powders with a very barge reactive surface area per unit weight and with a high bioavailability in humans. At the same time such powders have not been commercially

Methods Subjects Altogether, 72 subjects, 33 men and 39 women, volunteered for these eight studies. All subjects were healthy volunteers aged 20-49 y and each group included both men and women.

Some ofthe which

subjects

provided

Fe absorption tion

about

in each group were regular

a reasonable

(Table

range

1). Subjects

the aims

and

procedure

of intersubject

variation

were given written of the study.

were approved by the Ethical Commiuee ulty ofthe University of G#{246}teborg. Experimental

blood donors,

The

in

informaprojects

of the Medical

Fac-

design

The 59Fe-labeled ferric orthophosphates (complex [studies 1-6] or plain crystalline or amorphous [studies 7 and 8]) were used to fortify wheat flour. The native Fe in the wheat flour was

labeled by adding a trace amount of55Fe-labeled ferric chloride (FeCI3). Wheat rolls were baked from this doubly labeled flour except

The morning

drink

in the two experiments

wheat

rolls

were

to subjects

was allowed

on cereal porridge. with different had fasted overnight.

served

who

for the first 3 h after serving

meals in the No food or

the meals.

The

same doubly radioiron-labeled meals were served on two consecutive mornings. Two weeks after the last serving a blood sample was drawn to measure “Fe and 59Fe and a whole-body count of 59Fe was also made. A reference solution of 59Fe-la-

beled ferrous

ascorbate

(3 mg Fe) was then given on

two

con-


questioned by several researchers (eg, Elwood et al [71). The commercial Fe powders used in the mid-1960s contained a barge proportion of coarse Fe particles and their dissolution rate in hydrochloric acid was slow. In recent years finer Fe powders have been used for fortifi-

ET AL

A COMPLEX TABLE

1 ofnative

Content

iron and fortification

Fe (three

different

FERRIC

ferric

ORTHOPHOSPHATE

orthophosphates)

in study

meals

Study

meal

Nonhe Native

from these

Added Fe (59Fe)

Relative bioavailability (59Fe:55Fe)t

me Fe content Added

Total

Native Fe (“Fe)

mg I Breakfast with bread,* marmalade, coffee

and absorption

Fe sources

iont

Absorpt

Number and sex of subjects

131

Reference-dose absorptiont

%

%

9 M [5), 1 F

0.2

2.2

2.4

3.8 (0.4-17.9)

2.2 (0.2-8.6)

0.63

±

0.04

29.4 (1 1.2-68.S)

5 M [2], 6 F

0.2

2.7

2.9

3. 1 (0.7-14.2)

0.9 (0.2-8.6)

0.37

±

0.04

34.3 (20.8-70.1)

3 M [2J, 5 F [1]

0.2

13.9

14. 1

19.4 (6.5-42.7)

5.7 (1 .4- 14.7)

0.30

±

0.05

34.2 (14.6-S6.0)

4 M, 4 F

0.2

13.9

14. 1

36.8 (20. 1-63.5)

0.3 1

±

0.03

3.6(16.8-76.9)

1 M [ I ], 7 F

0.9

3.6

4.5

3.5 ( 1.2-6.2)

2.3 (0.5-3.5)

0.63

±

0.05

28.9(18.8-46.2)

1 M [ 1], 7 F

0.9

3.6

4.5

3.8 (2.0-6.2)

2.5 ( 1 .1-4.8)

0.64

±

0.03

29.9 ( I 2.8-71.8)

8 M [2J, 1 F [1]

0.2

2.2

2.4

2.2 (0.4-8.2)

0.2 (0.05-0.6)

0. 10

±

0.0 1

19.6 (1 1.1-34.4)

2 M [lJ, 8 F [I]

0.2

2.2

2.4

4.6 (0.6-12.9)

1.2 (0.2-2.6)

0.33

±

0.03

27.9(9.2-62.0)

(complex FePO4)

10.9 (5.9-24.

1)

FePO4)

6 Infant

cereal

(complex

FePO4)

7 Breakfast with bread, margarine, marmalade, coffee (plain FePO4, crystalline)

8 Breakfast

with bread,

margarine,

marmalade, coffee (plain FePO4,

amorphous) a

Number

ofregular

blood

donors

given

in brackets.

t j: range in parentheses. ti±SEM. § Vehicle for the fortificant. secutive

mornings

after

count

whole-body

an overnight

fast and

was done to measure

2 wk later

the retention

a new

ofthe

reference doses. All procedures and methods of calculation were described previously (1 1, 14). Because the 55Fe added as 55FeCl3 to the wheat flour uniformly labels the nonheme Fe pool in the meals studied, the ratio of the fractions of administered 59Fe and 55Fe that have been

absorbed

59Fe-labeled This fraction absorption

will be a direct

measure

of the fraction

of the

ferric phosphate thatjoined the nonheme Fe pool. is quite independent of the magnitude of the Fe and is a measure ofthe bioavaibability of phosphate

Fe in relation to the bioavailability ofan easily soluble Fe cornpound, eg, ferrous sulfate, known to mix completely with the nonheme Fe pool when it is added as a fortificant. The term relative bioavailability has therefore been used as a synonym for the 59Fe-55Fe

ratio.

In two studies (#3 and #4) the Fe fortificant was added to the meat broth to test the feasibility ofusing meat-broth powder as a vehicle for Fe fortification. In one of these studies (#4) 25 mg ascorbic bioavailability

acid was added to examine ofthe Fe fortificant.

its influence

Meal

composition

and preparation

Fe

on the

The rolls in all the studies were made from 40 g unfortified wheat flour of 60% extraction, yeast, sugar, and table salt. Weighed amounts of the labeled fortification Fe (CFOP or plain crystalline or amorphous femc orthophosphates) were carefully

mixed

20 g wheat

with

flour

in a glass

beaker.

This

labeled flour (premix) was then mixed with the rest ofthe flour needed. This procedure was necessary to ensure a uniform distribution of the fortification Fe in the flour. The dough was fermented for 30 mm at 23 #{176}C. It was then kneaded, and carefully weighed

amounts

were transferred standing

for

(Mettler

to small

10 mm

direct-reading

aluminium

for further

balance

forms

fermentation.

The

baked

at 250 #{176}C for 15 mm. The coffee breakfast

sisted

of one wheat

roll with

margarine

which

bread

cheese

rnL) in addition The meat-broth

Kempttal,

(15 g), corn

flakes

(20 g), and sour

to the roll with margarine meal

Switzerland).

consisted

of200

The labeled

left was

meal #1 con-

( 12 g), orange

bade ( 10 g), and coffee (I 50 mL). The coffee breakfast contained

P 2000)

were

manna-

meal #2 milk

(150

(Maggi

AG,

and coffee. rnL broth

fortification

Fe was added


2 Breakfast with bread, margarine, cheese, sour milk, corn flakes, coffee (complex FePO4) 3 Meat broth with bread (complex FePO4) 4 Meat broth with bread and 25 mg ascorbic acid (complex FePO4) 5 Infant cereal (complex

HALLBERG

132 while

the

bouillon

roll was served

cube

was

together

processed.

One

with the broth.

unfortified

The infant

cereal

wheat

content

(Sem-

tion

per 3, Semper, Stockholm, Sweden) was a whole-grain product mL per serving). In all the studies the same doubly radio-

(300

iron-labeled ings. Each MBq “Fe. Chemical

meal

meal

was

served

was labeled

on

two

consecutive mornMBq 59Fe and 0.074

with 0.056

ET AL ofthe

Gingerbread

of meals

Aliquots of the meals were freeze-dried and then finely ground to a powder in a porcelain mortar. Weighed amounts of this powder were analyzed for total Fe (14). Table 1 shows

the contents

of native

Fe, added

Fe, and total Fe in all meals

studied.

This

test

doses

of Fe

of0.056

Preparation

MBq

with

Fe(II)

were

lic Fe in 10 g concentrated

59FeCl3

was added

prepared

with

acid.

to prepare

the solution

The

Fe(II)

peroxide.

was then

Radioiron

the radioactive

as com-

with I 70 mL water and heat-

ing it to 90 #{176}C, amorphous

femc orthophosphate was obtained. A precipitate was formed which was washed with water and dried. To prepare crystalline ferric orthophosphate the solution with the amorphous product was boiled for 1 h. The precipitate of crystals was washed with water and dried. The amorphous

and the crystalline phosphate

products

in the Food

Preparation

ofthe

met

Chemical

complexferric

The complex femc 6H20 (CAS 38685-32-4),

the

specifications

Codex

1981

orthophosphate

orthophosphate, was prepared

for

ferric

(15).

(CFOP)

Fe3H8(NH4XPO4)6. from

solutions and solid

of 1 5 mol

a reaction

between

to flour

cloves,

and was left standing estimation unfortified

Fe dissolved

and Fe-binding

cinnamon,

and

from

polyphenols

ginger)

used

in the

at room

temperature.

After

30 mm an

ofthe blackish-brown discoloration was made using and ferrous sulfate-fortified gingerbreads as refer-

To

further

calibrate

fortified

the

to the same

fumarate.

test,

gingerbread

Fe level with

was

metallic

Six independent

also

made

Fe (carbonyl

observers

graded

Results Relative dfferent

bioavailability meals

ofthe

CFOPgiven

in Table 1 the relative bioavaibability of the was different in different meals. In a conti-

type ofbreakfast with coffee Fe and 4.5% ofthe fortification

The mean was 0.63

with

value

ofthe

± 0.04.

This

individual means

that

(study 1), 7. 1% of the Fe were absorbed.

absorption-ratio 63%

ofthe

values Fe in CFOP

joined the nonheme Fe pool. When the same wheat rolls, identically fortified, were served with a breakfast meal also containing sour milk and corn flakes and the bread was served with cheese instead of marmalade (study 2), the relative bioavaibabibity decreased to 37 ± 4% (p < 0.00 1). The total amount ofFe absorbed from the first continental-type breakfast was more than three times higher than from the breakfast that contained sour milk and corn flakes. When the fortification Fe was given with bread and meat broth (study 3), the relative bioavailability ofCFOP

was

30 ± 5%.

H3PO4/L, 15 mob NH3/L, 5.4 mob FeCIilL, NHCI. In the first step FeCI3 was added to the slightly acidic solution of H3PO4, NH3, and NH4C1. An amorphous precipitation was ohtamed. The crystalline CFOP was then formed from the amorphous phase in the next step by increasing the temperature. The crystals were then washed with water and dried. In each batch produced the compound was identified using x-ray diffraction. Xray data for Fe3H8(NH4XPO4)6 . 6H20 were published previously (16). Further details about the preparation were published in Chemical Abstracts (CAS 38685-32-4) and elsewhere (1 7). To prepare radioactive CFOP, radioiron was added as a trace amount of5FeC13 in the first stage ofthe synthesis.

In studies 5 and 6 the fortification Fe was included a cereal gruel and 63 ± 5% and 64 ± 3%, respectively, the added CFOP was available for absorption.

Measurement

Reproducibility

ofdissolution

The dissolution 1 I .5, 2, and ,

rate

rate was studied

3. Weighed

amounts

in hydrochloric acid at pH of the compounds, corre-

sponding to 1 5 mg elemental Fe and 50 mL HC1, in a 250-mL flask at 37 #{176}C by horizontal agitation 60 mm, frequency 100 cpm). Duplicate 2-mL withdrawn at various intervals. The samples were

filtered

through

a Millipore#{174}filter(Milbex-GS

were shaken (amplitude

samples

[0.22

were

immediately

z1). The Fe

the

discoloration.

nental native

1 g metal-

on

(ground

As shown Fe in CFOP

by dissolving

hydrogen

at this stage

By diluting

received

orihophosphates

phosphoric

to Fe(III)

pounds.

Each subject

59Fe.

ofradioiron-labeledferric

Solutions

oxidized

dose.

absorp-

Effect

ofadding

ascorbic

in of

acid

In study 4 ascorbic acid (25 mg) was added just before an identical meal as in study 3 was served, composed of bread and meat broth. The relative bioavaibabibity of the fortification Fe was the same 3 1 ± 3% as in study 3 (30 ± 5%).

Ascorbic

bioavaibability

bioavailability

acid

ofthe

thus

ofdeterminations ofthe

had

no

effect

on

the

relative

CFOP. of relative

CFOP

In studies 5 and 6 the relative bioavailability of the CFOP was studied in a cereal gruel fortified with the same batch of Fe. The cereal gruels in studies 5 and 6 were separately made on two occasions. The relative bioavailability

figures

were

63 ± 5% and

64 ± 3% in the

two


for 3 h after the reference

ofatomic

Fe infortzfiedflour

Fe added

Fe) and ferrous

A solution of 10 mL 0.01 mol hydrochloric acid/L containing 3 mg Fe as ferrous sulfate and 30 mg ascorbic acid was used as a reference in all studies. The 10-mL vials containing the Fe solution were rinsed twice with water which was also consumed. Each subject received two reference doses on two consecutive mornings after an overnight fast. No food or drink was

by means

gingerbread. The test is used as a quabitative-serniquantitative test of the presence of reactive Fe in the fortified flour. The gingerbread dough was rolled out to a thickness of ‘-2 mm

offlour

a total

is based

the fortification

ences.

Oral reference

was analyzed

test ofreactive

in the spices

composition

allowed

filtrate

spectrophotometry.

A COMPLEX TABLE

FERRIC

ORTHOPHOSPHATE

133

2

Proportion

ofthree

different

ferric orthophosphates

dissolved

after 30, 45, and 60 mm at different

pH 1.0 Type of ferric orthophosphate

30 mm

pH

pH 1.5

45 mm

60 mm

30 mm

pH 2.0

pH 3.0

45 mm

60 mm

60 mm

60 mm

%

Complex

(CFOP)

Amorphous

Crystalline

studies. The reproducibility tive bioavailability was Relative compared

80

89

95

53

64

69

0

0

27

45

55

17

30

38

0

0

5

5

6

0

0

0

0

0

in the determination very high.

thus

bioavailability ofplainferric with the CFOP

The

crystalbine

preparation

of rela-

orthophosphates

of plain

ferric

relative

orthophos-

,

testforfree

and

the variation

in the same

subject,

studied

on

bioavaibability

is probably

rebated

by the studies

reproducibility 5 and 6 when

of the

mean

the same

occasions. Ferric orthophosphate

meal

values

obtained

was studied

is not used today

but it is widely used as a fortificant because it is white, and insoluble,

Fe ions

to differences

in rate and extent of dissolution of the fortification Fe in the gastrointestinal tract before absorption is finished. The accuracy of the method used to determine the relative bioavailability is illustrated not only by the bow statistical variation observed in all studies (#1-8) but also

ofother and inert

in

on two

to fortify

flour

food products at the normal

There was no detectable discoloration of the gingerbread using the CFOP or carbonyl Fe as fortificants. The addition of ferrous fumarate, however, gave a distinct discoloration roughly graded as half the intensity ohserved in the gingerbreads fortified with ferrous sulfate.

pH of most foods. The relative bioavailability of ferric orthophosphate was studied previously in two laboratories with a method similar to that of the present study and employing two different radioiron isotopes. In one study of eight subjects ( 12) an arithmetic mean value of 32.3%

was observed

Solubilitv ofthe different types in relation to bioavailability

other

study

Table

2 shows

dependent and plain compounds.

that

offerric

orthophosphate

the sobubility

much

higher

was very

for

the

CFOP

much than

pHfor

the

main

findings

of a well-defined tive bioavailabibity

two

and relative

tab Fe powder) used the same

from

these

studies

molecule of a CFOP was 1) significantly

preparations

crystalline than the

of plain

ferric

observed technique,

Within noted

each between

study subjects

in the previous

ofa

there

preparation

were that its rebahigher than for

orthophosphate

(one

2) significantly higher of carbonyb Fe (ebemen-

one amorphous), bioavaibabibity

in a previous study (1 1) that and 3) influenced by the com-

position of the meal containing the to a lesser degree than with carbonyb ability

bioavailability and in anthe mean value was 7. 1%. These values are thus ofthe same magnitude as the 10% and 33% observed in the present study for the two batches of plain ferric orthophosphate (studies 7 and 8, respectively).

( 1 8)

subjects

The observation that ascorbic acid did not increase the relative bioavailability of the CFOP (studies 3 and 4) is in accordance with our previous observation ( 1 1) that

Discussion The

for relative

on seven

the

fortification Fe (1 1).

variation was

studies

very

in relative small.

ofcarbonyl

This

Fe that

same method (1 1). The probable main reason is that the marked variation in Fe absorption

Fe but

bioavaibwas

also

ability ascorbic

is no effect

ofascorbic

of carbonyl acid

used

Fe and in foods

acid

on the

that have

the

relative

small

no effect

bioavaib-

amounts

of

on the dissobu-

tion rate of Fe in vitro on any of these compounds (ebemental Fe powders or different ferric orthophosphates) at a given pH. On the other hand, ascorbic acid has a significant effect on the absorption of Fe from the fraction of the fortification Fe that is dissolved and has thus joined the nonheme Fe pool. Compared with the absorption in study 3, the 25 mg ofascorbic acid added in study 4 increased absorption by 21%. Figure 1 shows a comparison of the relative bioavail-

used the

ability

for this between

given in different meals. For comparison, results for carbonyb Fe from our previous

of the

CFOP

obtained

in this

study

when

it was

corresponding study ( 1 1) are


phate had a relative bioavailability of 10 ± 0.9% (study 7) and the relative bioavaibabibity ofthe amorphous preparation was 33 ± 3% (study 8). The studies were made on a continental-type breakfast identical to the one used in study 1 in which the CFOP had a relative bioavailabibity of 63 ± 5%. The relative bioavailability of the Fe in the CFOP was thus significantly higher than the Fe in the plain ferric orthophosphate preparations. (p < 0.00 1 and < 0.005, respectively). Gingerbread

subjects

different days, do not affect the ratio between the absorption of the fortification Fe in the nonheme Fe pool and the absorption of the native Fe originally present in the nonheme Fe pool. The main source of variation of the

HALLBERG

134

ET AL

Relative

absorbability

Meat-broth and bread

Breakfast and mibk

w. bread sour milk,

Breakfast bread and

with coffee

cornflakes and

Carbonyl

-

iron

CFOP

FIG 1. A comparison ofthe relative bioavailability carbonyl Fe (1 1) given with different types ofmeals. pool ofnative Fe in the meal.

A complex

-

(absorbability)

ing

milk

(sour

milk

and

cereals).

This

orthophosphate

of the complex ferric orthophosphate and the absorption from the nonheme

The 100% value represents

also shown. The breakfast meals were identical and the meat-broth meals were almost the same in both studies. In Figure 1 the bioavailability ofcarbonyl Fe given in the breakfast meal with milk is compared with the bioavailability of the CFOP given with a breakfast also containcomparison

done on the assumption that milk has a strong action on the pH of the gastric content and

femc

the Fe

affect the dissolution rate of Fe. The main points shown in Figure 1 are that the relative bioavailability of Fe of both CFOP and carbonyl Fe is affected by the meal cornposition and that the relative bioavailability of CFOP is much higher than that ofcarbonyl Fe, with a ratio of 3.2 for the continental breakfast, 6.0 for the meat broth and bread, and 4. 1 for the two breakfast meals containing milk. It may be estimated that, from the whole diet, “-4-

is

buffering may thus

Compl#{233}x (CFOP) .

C C 0 C 0.

L17 40

A

.0 C C C 0 0

10.-ed--

Crystalline 0

.

0

I 10

.

I 20

30

40

50

Per cent dissolved FIG

fraction joining

2. Relationship (%) dissolved the nonheme

60

70

80

90

after 45 minutes

between solubility offortification Fe and bioavailability in humans. Solubility is expressed after 45 mm at pH 1 and 37 #{176}C. Relative bioavailability is the fraction (%) of fortification Fe pool (see Fig 1). The studies were made on a continental-type breakfast with coffee.

as Fe


Carb

coffee

COMPLEX

A

4.5 times

more

Fe is absorbed

on average

than from carbonyl Fe. For carbonyl Fe the overall availability

related

to

from

FERRIC the CFOP

KL,

The

variation

meal

in relative

composition

was

bio-

fivefold

Fe.

relationship

availability ues graphed

between

dissolution

in man is shown show an almost

rate

in Figure 2 The linear relationship,

and

bio-

45-mm valboth for

the pH 1 and the pH 1.5 values, suggesting that conditions after 45 mm at pH 1.0-1 .5 may well correspond to in vivo conditions for the physiological dissolution of these

compounds.

has good

compatibility

properties

age of flour and does not interfere with the cess (Juveb AB and Kungs#{246}rnen AB, personal

cation,

1988).

The gingerbread

during

stor-

baking procommuni-

test is considered

to be a

sensitive screening test for compatibility ofFe fortificants with flour. It was developed and is used by milling laboratories in Sweden. The negative results obtained with this test agree with results from the storage and baking studies.

There used

tion

are two sets ofrequirements

in the

fortification

is known,

of flour.

acceptably

eds. Iron fortification

offoods.

Orlando,

FL: Academic

Press,

high,

for Fe preparations One

and

is that

the

absorp-

not too variable;

the

2. Cook JD, Reusser ME. Nutr l983;38:648-59. 3. Swiss LD, fortification.

Iron

fortification:

an

Beaton GH. A prediction of Am J Clin Nutr 1974; 27:373-9.

update.

the

Am

effects

J Clin

of

4. Martin HF, Halton P. Addition of different iron salts to flour: factor ofrancidity. J Sci Food Agric 1964; 15:464-8. 5. Steinkamp R, Dubach R, Moore CV. Studies in transportation and metabolism. VIII Absorption ofradioiron iron-enriched bread. Arch Intern Med 1955;95:181-93.

6. Elwood PC. The role of food iron in the prevention of nutritional anaemias. In: Blix G, ed. Occurrence, causes and prevention of nutritionalanaemias. Uppsala, Sweden: Almqvist & Wiksell, 1968: I 56-65. 7. Elwood PC, Newton D, Eakins JD, Brown DA. Absorption from bread. Am J Clin Nutr 1968;21:l 162-9. 8. Pla

GW,

biological

Fritz

JC,

availability

OffAnal

Chem

Rollingson and

CL.

solubility

Relationship rate

of iron

between

of reduced

the

J Assoc

iron.

1976;59:582-3.

9. Shah BG, Givoux A, Belonje a food additive. J Agric Food

B. Specifications for reduced Chem 1977;25:592-4.

iron as

10. Sacks PV, Houchin DM. Comparative bioavailability of elemental iron powders for repair of iron deficiency anemia in rats. Studies on efficacy and toxicity ofcarbonyl iron. Am J Clin Nutr 1978; 31: 566-73.

1 1. Hallberg L, Brune M, Rossander L. Low bioavailability ofcarbonyl iron in man: studies on iron fortification ofwheat flour. Am J Clin Nutr l986;43:59-67. 12. Cook JD, Minnick V, Moore CV, Rasmussen A, Bradley WB, Finch CA. Absorption of fortification iron in bread. Am J Clin Nutr l973;26:861-72. 13. BjOrn-Rasmussen

14. Hallberg L. Food iron absorption. In: Cook JD, hematology. London: Churchill, 1980: 1 16-33.

ed. Methods

ertness ments

15. National Academy of Sciences. Food Chemical Washington, DC: National Academy Press, 1981.

Codex.

here,

however,

meets

It is actually doubtful Fe compounds that possible combination flour, ie, insolubility, insolubility,

and

good

both

sets ofrequirements

requirestudied very

well.

whether it is possible to find other better comply with the almost imof claims for Fe fortificants of inertness, which is basically due to bioavailabibity

in humans.

B

References 1. Hallberg L. Factors influencing the efficacy ofiron fortification and the selection of fortification vehicles. In: Clydesdale FM, Wiemer

the iron from

second is that the Fe preparation does not cause undesirable changes in the flour during storage or in the baked products. This means that the preparation must be insoluble in water and stable under prevailing storage conditions. Elemental Fe powders, of which the carbonyl Fe previously studied represents the best, fulfill only the in-

requirements whereas the bioavailability are not acceptably satisfied. The CFOP

iron

fortification

E, Hallberg iron.

L, Rossander

Bioavailability

reduced iron and prediction Nutr l977;37:375-88.

in man

ofthe

effects

L. Absorption

of different

ofiron

16. Haseman iF, Lehr JR. Smith JP. Mineralogical iron and alumunium phosphates containing ammonium. Soil Sci Soc Proc 1951; 15:76-84.

of

samples

fortification.

of

Br J in

3rd ed.

character of some potassium and

17. Torstensson LG, Dahlqvist PA, Benjelloun M, inventors; Eka Nobel AB, assignee. Use ofiron (III) fortification offood products. Sweden. Swedish patent 8601880-1. April 23, 1986. International patent application WO 87/06433. 18. Disler

PB, Lynch

fortification

SR. Charlton

of cane

1975;34: 14 1-52.

sugar

with

RW,

Bothwell

iron

and

ascorbic

TH.

Studies acid.

on the

Br J Nutr


CFOP

135

1985:17-28.

(range 5-25% for different meals and levels of Fe fortification) and was thus more marked than the approximateby twofold variation in bioavailability noted in this paper for the CFOP (0.30-0.63). These findings merely illustrate that the higher the relative bioavailability the lower is the expected variation in absorption and the better the possibility of predicting the effect of an addition offortification

ORTHOPHOSPHATE