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Phytic acid added to white-wheat bread inhibits fractional apparent magnesium absorption in humans

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Phytic acid has been reported to impair the absorption of minerals and trace elements such as calcium, zinc, and iron in humans. However, limited information is available on the effect of phytic acid on magnesium absorption. The objective was to evaluate the effect of phytic acid on fractional apparent magnesium absorption in humans. Two stable-isotope studies were performed with 8-9 healthy adults per study. Test meals were based on 200 g phytic acid-free wheat bread; test meals with and without added phytic acid were served on days 1 and 3 according to a crossover design. Phytic acid was added in amounts similar to those naturally present in whole-meal (1.49 mmol) and in brown bread (0.75 mmol). Each test meal was labeled with 0.7 mmol (25)Mg or 1.1 mmol (26)Mg. The total magnesium content was standardized to 3.6 mmol in all test meals. Apparent magnesium absorption was based on fecal monitoring. The addition of phytic acid lowered fractional apparent magnesium absorption from 32.5 +/- 6.9% (no added phytic acid) to 13.0 +/- 6.9% (1.49 mmol added phytic acid; P < 0.0005) and from 32.2 +/- 12.0% (no added phytic acid) to 24.0 +/- 12.9% (0.75 mmol added phytic acid; P < 0.01). The inhibiting effect of phytic acid was dose dependent (P < 0.005). The results show that fractional magnesium absorption from white-wheat bread is significantly impaired by the addition of phytic acid, in a dose-dependent manner, at amounts similar to those naturally present in whole-meal and brown bread.
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Phytic acid added to white-wheat bread inhibits fractional apparent
magnesium absorption in humans
1–3
Torsten Bohn, Lena Davidsson, Thomas Walczyk, and Richard F Hurrell
ABSTRACT
Background:Phyticacidhasbeenreportedtoimpairtheabsorption
of minerals and trace elements such as calcium, zinc, and iron in
humans. However, limited information is available on the effect of
phytic acid on magnesium absorption.
Objective:Theobjectivewas to evaluate the effect of phytic acid on
fractional apparent magnesium absorption in humans.
Design: Two stable-isotope studies were performed with 8–9
healthy adults per study. Test meals were based on 200 g phytic
acid–freewheatbread;testmealswithandwithoutadded phytic acid
were served on days 1 and 3 according to a crossover design. Phytic
acid was added in amounts similar to those naturally present in
whole-meal(1.49 mmol) and in brownbread (0.75 mmol). Each test
meal was labeled with 0.7 mmol
25
Mg or 1.1 mmol
26
Mg. The total
magnesium content was standardized to 3.6 mmol in all test meals.
Apparent magnesium absorption was based on fecal monitoring.
Results: The addition of phytic acid lowered fractional apparent
magnesium absorption from 32.5 6.9% (no added phytic acid) to
13.0 6.9% (1.49 mmol added phytic acid; P0.0005) and from
32.2 12.0% (no added phytic acid) to 24.0 12.9% (0.75 mmol
addedphyticacid;P0.01).Theinhibitingeffectof phytic acid was
dose dependent (P0.005).
Conclusion:Theresultsshowthatfractionalmagnesiumabsorption
from white-wheat bread is significantly impaired by the addition of
phyticacid, in a dose-dependent manner, at amountssimilartothose
naturally present in whole-meal and brown bread. Am J Clin
Nutr 2004;79:418–23.
KEY WORDS Magnesium absorption, phytic acid, wheat
bread, stable isotopes, fecal monitoring
INTRODUCTION
Phytic acid, myo-inositol hexakisphosphate, is widely distrib-
uted in nature because it is the major storage form of phosphorus
in cereals, legumes, and oil seeds (1). It is typically found in the
outer (aleuron) layers of cereal grains and in the endosperm of
legumesand oil seeds. For example,cereal products such as bran
andwhole-mealbreadarerich in phytic acid (2). The daily intake
of phytic acid has been estimated to be 200800 mg in indus-
trialized countries and 2 g in developing countries (3).
Although an inhibiting effect of phytic acid on mineral and
trace element absorption has been reported for iron, zinc, cal-
cium,and manganese (4–10), information on the effectof phytic
acid on magnesium absorption is limited. Negative magnesium
balances were reported to correlate with dietary phytic acid in-
take, on the basis of observations in 2 human subjects (11), and
magnesium absorption was shown to be significantly impaired
when phytic acid was added to white-wheat bread (12). In addi-
tion, chemical balance studies have indicated significantly in-
creased magnesium absorption after dephytinization of bran
muffins (13). However, the dose-dependent effect of phytic acid
on magnesium absorption has not been evaluated with the use of
isotopic techniques in humans.
The aim of the present study was to evaluate the effect of
phytic acid on magnesium absorption in adult humans. Test
meals were based on phytic acid free–white-wheat bread; phytic
acid was added to simulate the native content of phytic acid in
whole-meal and brown-wheat bread. Fractional apparent mag-
nesiumabsorptionwasevaluatedwitha stable-isotope technique
based on extrinsic labeling of the meals and fecal monitoring of
the excreted labels.
SUBJECTS AND METHODS
Subjects
Twenty (10 women and 10 men) apparently healthy free-
living adults were recruited. Exclusion criteria included preg-
nancy and lactation. No medication, except for oral contracep-
tives, was allowed during the study. Intake of mineral and
vitamin supplements was not permitted 2 wk before the start of
and during the study. All subjects were informed about the aims
and the procedures of the study orally and in writing, and written
informed consent was obtained from all participants. The partic-
ipants were instructed not to change their dietary habits or life-
style during the study. The study protocol was reviewed and
approvedbythe Ethical Committee at the SwissFederalInstitute
of Technology, Zurich.
Isotopic labels
Highly enriched
25
MgO (1.04 0.01%
24
Mg, 98.73 0.01%
25
Mg,and0.230.01%
26
Mg)and
26
MgO(0.390.01%
24
Mg,
1
FromtheLaboratoryforHumanNutrition,InstituteofFoodScienceand
Nutrition, Swiss Federal Institute of Technology, Zurich.
2
Supported by the Swiss Federal Institute of Technology (grant
41-2701.5).
3
Reprints not available. Address correspondence to L Davidsson, Labo-
ratory for Human Nutrition, Institute for Food Science and Nutrition,
Seestrasse 72, PO Box 474, 8803 Ru¨schlikon, Switzerland. E-mail:
lena.davidsson@ilw.agrl.ethz.ch.
Received May 15, 2003.
Accepted for publication August 4, 2003.
418 Am J Clin Nutr 2004;79:418–23. Printed in USA. © 2004 American Society for Clinical Nutrition
0.11 0.01%
25
Mg, and 99.50 0.01%
26
Mg) labels were
purchased from Chemotrade (Du¨sseldorf, Germany). The en-
riched
25
Mglabel(28 mmol as
25
MgO)and
26
Mglabel(43 mmol
as
26
MgO) were dissolved in 10 mL of 4 mol HCl/L and diluted
to 100 mL with water. Solid NaHCO
3
(Merck, Darmstadt, Ger-
many) was added to adjust the solution to a pH of 6. Concentra-
tions of the
25
Mg and
26
Mg isotope labels in solution were de-
termined by isotope dilution mass spectrometry against a
commercialmagnesiumstandardofnaturalisotopic composition
(Titrisol;Merck).Unlessotherwisespecified,all chemicals were
of analytic grade, and acids were further purified by surface
distillation. Only 18 Mwater (Milli Q Water System; Milli-
pore, Zurich, Switzerland) was used for the laboratory analyses
and test meal preparation.
Test meals
All test meals were based on 200 g phytic acidfree white-
wheat bread. Bread rolls were prepared by mixing 1 kg white-
wheat flour (Migros, Zurich, Switzerland) with water (600 g),
salt (10 g), sugar (32 g), and dry yeast (15 g). The dough was left
to ferment for5hatroom temperature. The bread rolls were
baked for 15 min at 200 °C. Individual servings were weighed
andstoredfrozen(Ҁ25 °C)untilserved.Themagnesiumcontent
of all test meals was standardized by adding a solution of MgCl
2
(Merck) to the white-wheat bread before serving. Phytic acid in
its dodecasodium form (Sigma, Buchs, Switzerland) was dis-
solved in water (73.5 mmol/L), and aliquots of phytic acid and
stable-isotope labels in solution were pipetted onto the wheat
bread 1 h before administration. The rare earth elements ytter-
bium and europium (in chloride form; Aldrich, Buchs, Switzer-
land) were added to 600 mL water, which was served as a drink
with the labeled bread.
Study design
A fecal sample was collected to determine baseline magne-
sium isotope ratios before intake of the labeled test meals. Bril-
liant blue (100 mg; Warner Jenkinson Europe, Kings Lynn,
UnitedKingdom),adyeusedasafecalmarker,was administered
in a gelatin capsule on the day before intake of the first labeled
test meal to indicate the start of the fecal pooling. After the
subjects fasted overnight, a venous blood sample (10 mL) was
drawn into a heparin-treated glass tube (Evacuated Tube Sys-
tems, Plymouth, United Kingdom) for the measurement of
plasma magnesium concentrations. Plasma was separated by
centrifugation(Omnifuge2.0RS; Heraeus, Zurich, Switzerland)
at 20 °Cand500҂g(5 min) and storedin acid-washed plastic
vials at Ҁ25 °C until analyzed.
Eachsubjectactedashisorherowncontrol.Twotestmeals(A
andB)wererandomlyallocatedtobeserved in each study on day
1orday3(Table1). Test meal A consisted of 200 g wheat bread
prepared from 150 g flour, to which phytic acid and
25
Mg were
added. Test meal B (no added phytic acid) consisted of 200 g
wheat bread labeled with
26
Mg (Table 1). Because of the lower
analytic precision in the measurement of
26
Mg/
24
Mg than in that
of
25
Mg/
24
Mg, a higher dose of
26
Mg was administered. Water
(600 mL) was served as a drink. Test meals were divided into 2
identical portions and served at breakfast (07300830) and
lunch (12001300) on the same day. No food or drink was
allowedbetween the intake of the 2 labeledtest meals and for3 h
after intake of the second labeled test meal served at lunchtime
(days 1 and 3). Standardized dinners (frozen pizza and white-
wheat crisp bread) and drinking water (2 L) were provided on
days 1 and 3. No additional food or drink was allowed on days 1
and 3. Diet was unrestricted at all other times.
Preweighed polypropylene containers (Semadeni, Oster-
mundingen,Switzerland)wereprovidedforstoolcollection.The
subjectscollectedallstoolsseparately,starting immediately after
intake of the first labeled test meal on day 1. On day 8, a second
brilliant blue capsule was administered. Fecal collections were
continued until excretion of the second brilliant blue marker.
Stool samples were stored frozen (Ҁ25 °C) until processed.
Preparation of fecal pools and mineralization
Each individual stool sample was freeze-dried (Modulyo; Ed-
wards,NorthBergen,NJ)andgroundtoapowderinamortar.All
stool samples, beginning with the first fecal sample dyed by the
firstbrilliant blue marker until,but not including, thestools dyed
by the second marker, were included in the fecal pool. After
undergoing a drying step in a drying chamber (Binder, Tuttlin-
gen,Germany)at20hat65 °Ctostandardizehumidity,followed
bycoolingatroomtemperature(4h),allindividualstoolsamples
were weighed and milled (mill with 1-mm pores, ZM1; Retsch,
Haan, Germany), starting with the first (most enriched) samples.
Milled fecal material was transferred back into its original con-
TABLE 1
Total magnesium content, added stable-isotope labels, added phytic acid, and molar ratio of phytic acid to magnesium in different test meals
1
Study 1 (n҃9) Study 2 (n҃8)
Test meal A Test meal B Test meal A Test meal B
Magnesium (mmol) 3.63 0.04
2
3.64 0.05 3.63 0.04 3.65 0.03
Stable-isotope label (mmol)
25
Mg 0.65 0.02 0.65 0.02
26
Mg 1.12 0.01 1.12 0.01
Phytic acid (mmol) 1.488 0.022 ND 0.746 0.002 ND
Phytic acid:magnesium (molar ratio) 0.41 ND 0.21 ND
Fecal marker (nmol)
Ytterbium 31.38 0.58 31.38 0.58
Europium 33.17 0.26 33.17 0.26
1
Test meals A and B were based on 200 g phytic acidfree white-wheat bread and 600 mL water served as a drink. Both meals, in each study, were served
as 2 identical portions at breakfast and lunch on days 1 and 3. ND, not detectable; the limit of detection was 0.5
mol/100 g.
2
xSD.
PHYTIC ACID INHIBITS MAGNESIUM ABSORPTION 419
tainer, dried again for 20 h at 65 °C, cooled for4hatroom
temperature,andreweighed.Allmilledstoolsamplesincludedin
a single pool were combined in a 2-L polyethylene container
(Semadeni) and mixed for 90 min with a rotator (UG 70/20;
Micro Motor, Basel, Switzerland). Aliquots of freeze-dried
pooledstoolsamples (1.01.6g),freeze-dried wheat bread (0.25
g), and plasma (1 g), were mineralized in a microwave digestion
system (MLS 1200; MLS GmbH, Leutkirch, Germany) in a
mixture of 14 mol HNO
3
/L and 8.8 mol H
2
O
2
/L (Merck). All
samples were mineralized in duplicate.
Separation of magnesium
Magnesiumwasseparated from the mineralized stool samples
by cation-exchange chromatography with a strongly acidic ion-
exchange resin (AG 50W X-8, 200400 mesh; Bio-Rad, Her-
cules, CA). Aliquots containing 30
mol Mg were evaporated
todryness,redissolvedin1mL of 0.7 mol HCl/L, and transferred
onto the top of a column (1-cm inner diameter; Bio-Rad) filled
with the ion-exchange resin to a height of 7 cm. The column was
rinsed with 56 mL of 0.7 mol HCl/L, followed by 24 mL of 0.9
mol HCl/L to elute sodium and potassium. Magnesium was
elutedwith12mLof1.4 mol HCl/L.Thesolutionwasevaporated
todrynessandredissolvedin 50
Lwater.Magnesiumrecovery,
evaluated with a diluted magnesium standard solution (Titrisol;
Merck), was found to be 94.8 1.8% (n҃10). Resins were
regenerated with 30 mL of 6 mol HCl/L and replaced after the
fifth run. Only acid-washed polytetrafluoroethylene and poly-
ethylene laboratory ware were used during sample processing.
Aliquotsofthe
26
Mgisotopelabelwereprocessedin parallel with
eachbatch for blank monitoring,from ion-exchange chromatog-
raphy onward. Sample contamination due to natural magnesium
was 10.8 7.0 nmol (n҃9) for combined sample preparation
and filament loading, which was 0.4of the amount of mag-
nesium separated.
Isotopic analysis by thermal ionization mass spectrometry
About 20 nmol Mg, separated from fecal samples, was loaded
onto the metal surface of the evaporation filament of a double-
rhenium filament ion source. Magnesium was coated with 510
g silica gel 100, 0.8
mol boric acid, and 30 nmol Al as AlCl
3
(all chemicals were from Merck). Compounds were loaded in
aqueous solution and dried electrothermally at 0.8 A after each
step.Finally,theevaporation filament was heated to dull red heat
(1.6 A) for 30 s. The ionization filament remained unloaded.
Isotope ratios were determined with a single-focusing magnetic
sectorfieldinstrument(MAT262;FinniganMAT,Bremen,Ger-
many) equipped with a Faraday cup multicollector device for
simultaneous ion-beam detection. The evaporation filament was
heated to 1230 °C according to a standardized procedure. The
ionization filament was heated gradually to 12501350 °C until
a stable Mg
ѿ
ion beam of 12҂10
Ҁ11
A was obtained. Each
measurementconsisted of 30consecutive isotope ratio measure-
ments. Repeatability (5 independent analyses) was 0.2% (rel-
ative SD) for the
24
Mg/
25
Mg isotope ratio and 0.4% for the
24
Mg/
26
Mg isotope ratio. A standard reference material (stan-
dard reference material 980; National Institute of Standards and
Technology, Gaithersburg, MD) was analyzed in parallel. The
results (0.12631 0.00029 for the
25
Mg/
24
Mg isotope ratio and
0.138760.00059 for the
26
Mg/
24
Mgisotope ratio) agreed with
isotope ratios from the International Union of Pure and Applied
Chemistry: 0.12663 0.00013 and 0.13932 0.00026, respec-
tively (14).
Magnesium analysis by atomic absorption spectroscopy
Quantitative magnesium analysis of the mineralized and di-
lutedsamplesofplasma,bread,andfecalmaterial was performed
by flame atomic absorption spectroscopy (SpectrAA 400; Var-
ian, Mulgrave, Australia). Plasma samples were measured by
external calibration with the use of a commercial magnesium
standard (Titrisol; Merck). All other samples were measured by
aninternal calibration technique (standardaddition)to minimize
matrix effects. In addition, all measured solutions contained
La(NO
3
)
3
at 5000 mg La/L to suppress precipitation of magne-
sium salts. Certified reference materialsSeronorm Trace Ele-
ments Serum (Nycomed, Oslo) and wheat flour 1567a (National
BureauofStandards,Gaithersburg,MD)wereanalyzedinpar-
allel. Ytterbium and europium were measured by electrothermal
atomic absorption spectroscopy by external calibration with the
use of a standard solution containing ytterbium and europium
(Titrisol; Merck). Mineralized fecal samples were diluted with 1
molHCl/L, and aliquots (10
L)were injected into pyrolytically
coated graphite tubes. Heating procedures and absorption wave-
lengths were used according to the manufacturer (15).
Phytic acid analysis
Samples of bread rolls were freeze-dried and ground in a
mortar.Phyticacid was extracted from a1-galiquotwith 0.5 mol
HCl/L. The extract was purified by anion-exchange chromatog-
raphy, evaporated to dryness, and redissolved in water before
analysis with the use of reversed-phase HPLC (16).
Calculations
Molaramounts and ratiosof the
25
Mgand
26
Mgisotope labels
in the samples were calculated on the basis of double-isotope
dilution principles (17, 18). Fractional apparent magnesium ab-
sorption was calculated on the basis of the dose (
mol) of the
stable isotope label of magnesium administered (D
o
) and the
amount of the label excreted in feces (F
o
).
AA(%) (DoFo/Do)100 (1)
The recovery of the rare earth elements ytterbium and europium
was used to evaluate the completeness of the stool collections.
Statistics
Calculations were made by using commercial software:
EXCEL 97 (Microsoft, Chicago) and SPSS 10.0 (SPSS Inc,
Chicago).Results are presented as arithmetic means SDs.The
normal distribution of magnesium absorption data was verified
with the use of the Kolmogorov-Smirnoff test. Homogeneity
between groups was tested by Levenes test. Paired Studentst
test (two-tailed) was used to compare magnesium absorption
fromthe 2 different test meals within eachstudy. The dose effect
of phytic acid on magnesium absorption was evaluated with the
use of an unpaired Studentsttest based on absorption ratios
(with/without added phytic acid). In addition, a linear mixed
model was used to evaluate the dose effect of phytic acid on
magnesiumabsorption.Thismodelincludedmagnesiumabsorp-
tion as the dependent factor and meal (with or without added
phytic acid) and study (1.49 or 0.75 mmol added phytic acid) as
420 BOHN ET AL
fixed factors. Subject, as a random factor, was nested within
study. Pvalues 0.05 were considered statistically significant.
RESULTS
Subjects and test meals
The ages and body mass indexes (in kg/m
2
) of the subjects
were 27 12 y and 22.1 3.8, respectively, in study 1 (n҃9)
and 24 2 y and 21.7 1.0 in study 2 (n҃8). Mean plasma
magnesium concentrations were 0.77 (range: 0.670.85)
mmol/L and 0.84 (range: 0.770.90) mmol/L in studies 1 and 2,
respectively. Two subjects had slightly lower magnesium con-
centrations (0.67 and 0.73 mmol/L) than the reported normal
range (0.750.96 mmol/L) (19).
Thenativecontentofphyticacidinthewheatbread was below
thedetection limit (0.5
mol/100g; n҃3). The nativecontent
of magnesium in the wheat bread was 0.96 0.03 mmol/100 g
(n҃3). The magnesium and phytic acid contents of the labeled
test meals are presented in Table 1.
Magnesium absorption
Addition of 1.49 mmol phytic acid to 200 g phytic acidfree
bread inhibited apparent magnesium absorption significantly:
32.56.9%(testmealA)comparedwith13.06.9%(testmeal
B) (P0.0005, Figure 1). One subject was excluded from the
evaluation because of a low recovery of ytterbium (85%). The
exclusion criteria were based on the estimated relatively high
combined uncertainty of the recovery of rare earth elements in
fecal material and on previous studies that used rare earth ele-
ments as fecal markers (20, 21). For all other subjects, mean
ytterbium recovery was 99.5% (range: 86.4107.1%) and mean
europiumrecoverywas 101.7% (range: 89.5116.3%). Addition
of 0.75 mmol phytic acid to 200 g bread inhibited magnesium
absorption significantly: 32.2 12.0% (test meal A) compared
with 24.0 12.9% (test meal B) (P0.01; Figure 2). Two
subjects were excluded from the evaluation because of low yt-
terbium recovery. For all other subjects, mean ytterbium recov-
ery was 105.4% (range: 97.5115.6%) and europium recovery
was96.9%(range:90.2120.6%).The inhibitory effect of phytic
acid on magnesium absorption was dose dependent (P0.005,
unpaired Studentsttest). On the basis of a linear mixed model,
a statistically significant effect of meal (with or without added
phyticacid; P0.001) on magnesium absorptionwas observed,
but no significant effect of study was observed (1.49 or 0.75
mmol added phytic acid). The study-by-meal interaction was
statistically significant (P0.005), which indicated that mag-
nesiumabsorptionwas significantly influenced by the amountof
phytic acid added to the meal.
The mean loss of fecal material during stool pool preparation,
determined by weighing the pools before and after milling, was
1.91.1%.The measured isotopic enrichment of the stoolpools
was 5.2 1.9% (
24
Mg/
25
Mg) and 8.4 2.7% (
24
Mg/
26
Mg) on
the basis of differences in the measured isotope ratios of fecal
pools and natural isotope ratios of a standard (Titrisol; Merck)
divided by the measured isotope ratio of the standard.
DISCUSSION
Mean fractional apparent magnesium absorption was 60%
lower when phytic acid was added to phytic acidfree white-
wheat bread at an amount similar to that in whole-meal wheat
bread (1.49 mmol/200 g) and 25% lower when added at an
amount similar to that in brown bread (0.75 mmol/200 g). The
inhibiting effect of phytic acid was dose dependent (P0.005).
Although this is the first time that the inhibition of magnesium
absorption by phytic acid was observed with single meals, such
an effect was indicated by chemical balance studies in humans
that evaluated phytic acid added to white bread (12) and dephy-
tinized bran (13). In these earlier studies, a somewhat more lim-
ited inhibitory effect of phytic acid on fractional apparent mag-
nesium absorption was found at molar ratios of phytic acid to
magnesium that were similar to those used in the present study,
ie, absorption of 13% and 38% at molar ratios of 0.2 and 0.4,
FIGURE1.Apparentfractional magnesium absorptionfrom200gwhite-
wheat bread with 1.49 mmol added phytic acid (test meal A) compared with
that from 200 g white-wheat bread with no added phytic acid (test meal B) in
9 subjects. Individual data are represented by triangles. The mean value is
indicated by the solid, horizontal line.
FIGURE2.Apparentfractional magnesium absorptionfrom200gwhite-
wheat bread with 0.75 mmol added phytic acid (test meal A) compared with
that from 200 g white-wheat bread with no added phytic acid (test meal B) in
8 subjects. Individual data are represented by triangles. The mean value is
indicated by the solid, horizontal line.
PHYTIC ACID INHIBITS MAGNESIUM ABSORPTION 421
respectively.However,itisimportantto stressthatthemagnitude
oftheinhibitoryeffect might have been influenced by the control
diets, which were not completely free of phytic acid, or by ad-
aptation to decreased dietary magnesium bioavailability.
Aswithiron,zinc,andcalcium,itisassumedthatmagnesium
phytic acid or protein-magnesiumphytic acid complexes are
formed in the intestine, which are insoluble at a pH 6 (2224)
and thus are not absorbable. However, the stability of the mag-
nesiumphytic acid complex is weaker than phytic acid com-
plexes with iron, copper, and zinc (25, 26). It is also important to
stress that endogenous losses of magnesium represent a signifi-
cant fraction of total magnesium losses and that phytic acid can
be expected to form complexes with both food magnesium and
endogenous magnesium in the gastrointestinal tract. However,
on the basis of rat studies, it is not certain whether the reabsorp-
tion of endogenous magnesium is inhibited by phytic acid (27,
28).
In the present study, all test meals were based on phytic acid
free wheat bread and differed only by whether phytic acid was
added.Wechosenottodephytinizewhole-mealandbrownbread
soastoavoidpotentialdifferencesbetweentestmealsbecauseof
differences in ingredients, food-preparation methods, or both.
The phytic acid content and molar ratios of phytic acid to mag-
nesiuminthetest meals were similar to those reported forwhole-
meal and brown bread. In whole-meal bread, the phytic acid
contentisreportedtobeintherange0.71.6mmol/100g,andthe
molar ratio is between 0.2 and 0.5; in brown bread, the corre-
sponding values are 0.10.4 mmol/100 g, and the molar ratio
is0.10.3 (2). The additionof phytic acid would seem a useful
approachtosimulatenativephytic acid because phytic acid com-
plexes are largely soluble at a pH of 23, as in the stomach, and
mineral binding is weak (23, 24). Thus, under these conditions,
an exchange of minerals bound to phytic acid can be expected to
occur. This approach was used previously in human studies, for
example, to evaluate the effect of phytic acid on iron absorption
(29). The magnitude of the inhibitory effect of added phytic acid
on iron absorption in the study by Hallberg et al (29) was similar
to that reported for native phytic acid by Hurrell et al (30).
Our data indicate that fractional magnesium absorption from
whole-mealandbrown bread is significantly inhibited compared
withthatfromphyticacidfree white-wheat bread. However, the
absolute amounts of magnesium absorbed from whole-meal and
brown bread can be expected to be higher than those from white
bread because of the 23-fold higher magnesium content (31),
unless other components in whole-meal and brown bread (such
as dietary fiber, minerals, and trace elements) influence magne-
sium absorption or modify to a great extent the effect of phytic
acid on magnesium absorption.
In conclusion, the results of the present study indicate that
fractional magnesium absorption from white-wheat bread is sig-
nificantly inhibited by phytic acid, in a dose-dependent manner,
when it is added at amounts similar to those naturally present in
whole-meal and brown bread.
Allauthorscontributed tothestudydesign. TBwasresponsiblefor thedata
collectionanddataanalysis.TWwaspartlyresponsibleforthedataanalysis.
The manuscript was prepared by TB and LD and revised by TW and RFH.
None of the authors reported any conflict of interest.
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PHYTIC ACID INHIBITS MAGNESIUM ABSORPTION 423
... Isolated tannin extract inhibit the αamylase and glucoamylase in vitro [118] Saponins Vernonia amygdalina (Lyse the erythrocyte) Saponin had high haemolytic effect on blood group-O and genotype-SS. [127] Neem (Azadirachta indica) Observed inhibition of amylase enzyme in T. castaneum insects after 4 days feeding [130] Phytic acid Wheat (Triticum aestivum) (Reduce the absorption of magnesium) Addition of phytic acid lowered the magnesium absorption in healthy humans, in a dose-dependent manner [133] Bean (Phaseolus vulgaris) Reduce the efficiency of iron absorption in the women subjects. ...
... Although the interactions of phytic acid with other minerals and micronutrients are much explored, the dosage-dependent manner of phytic acid on magnesium absorption is not that explored. But in a study, it was presented that, phytic acid, in the amount that it is normally present in the white wheat bread, can reduce the absorption of magnesium [133]. Magnesium is very crucial in numerous metabolic processes and the detections and exploration of dietary molecules that can affect the absorption of it are important in the view of nutrition science. ...
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Anti-nutrients are the biomolecules that if present in food along with nutrients, can reduce either the absorption or the utilization of nutrients. The physiological importance of anti-nutrients is been debated for a long time because the researches point at different effects on different anti-nutrients in foods. Some anti-nutrients show both beneficial and harmful physiological effects that depend on molar ratios between nutrients and anti-nutrients and some other factors. Previous studies suggested that anti-nutrients if are consumed in a healthy amount they may act as a useful natural drug to ameliorate human health. They can have physiological importance in the nutrition of the organism. In this review, we compiled the beneficial attributes of major plant-based anti-nutrients to improve health conditions, along with their potential adverse effects.
... However, the removal of phytic acid increases the bioavailability of many cations and thus the nutritional value of the meal. The digestive enzyme phytase can unlock the phosphorus stored as phytic acid, but in the absence of phytase, it can impede the absorption of other minerals like iron, zinc, magnesium, and calcium by binding to them due to chelating property (Hallberg et al. 1989;Reddy et al. 1996;Bohn et al. 2004;Phillippy 2006). This results in highly insoluble salts that are poorly absorbed by the gastrointestinal tract leading to lower bioavailability of minerals. ...
... An important aspect of the nutritional evaluation of a food or ingredient is the content of some antinutrient compounds. Phytates are known to contribute to decreasing the absorption of essential micronutrients, such as calcium, iron (Hurrell et al. 2003), zinc (Guttieri et al. 2006) and magnesium (Bohn et al. 2004;Peng et al. 2010). They also have a negative impact on protein digestibility because they can bond to dietary protein or digestive enzymes (proteases and amylases), inhibiting their hydrolytic activity (Espinosa-Páez et al. 2017;Muñoz-Llandes et al. 2019). ...
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Solid-state fermentation (SSF) may be a suitable bioprocess to produce protein-vegetal ingredients with increased nutritional and functional value. This study assessed changes in phenol content, antinutrient content, biomass production and protein production resulting from the metabolic activity of Pleurotus ostreatus , an edible fungus, in lentils and quinoa over 14 days of SSF. The impact of particle size on these parameters was also assessed because the process was conducted in both seeds and flours. Fungus biomass increased during fermentation, reaching 30.0 ± 1.4 mg/g dry basis and 32 ± 3 mg/g dry basis in lentil grain and flour and 52.01 ± 1.08 mg/g dry basis and 45 ± 2 mg/g dry basis in quinoa seeds and flour after 14 days of SSF. Total protein content also increased by 20% to 25% during fermentation, in all cases except lentil flour. However, the soluble protein fraction remained constant. Regarding phytic acid, SSF had a positive impact, with a progressive decrease being higher in flours than in seeds. Regarding antioxidant properties, autoclaving of the substrates promoted the release of polyphenols, together with antioxidant activity (ABTS, DPPH and FRAP), in all substrates. However, these parameters drastically decreased as fermentation progressed. These results provide scientific knowledge for producing lentil- or quinoa-based ingredients with low antinutrient content enriched with protein fungal biomass. Graphical Abstract
... Concerning the bioaccessibility of minerals determined by the dialysis assays, the formulations made with the addition of RBF presented better bioaccessibility, and formulation F1 was the most promising. This result is probably due to the higher concentration of phytates and fibers in the formulations with WGBF (F2 and F4), which have the ability to bind to minerals (Fe 2+ , Ca 2+ , Zn 2+ ) and consequently decrease the absorption in the human body (Bohn et al., 2004). Steadman et al. (2001) evaluated the contents of minerals, phytic acid, tannins, and rutin in different milling fractions of buckwheat grains. ...
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The nutritional quality and bioactive potential of breads made with partial replacement of refined wheat flour (RWF) with 30% or 45% refined buckwheat flour (RBF) or whole buckwheat flour (WGBF) was assessed through mineral bioaccessibility, starch digestibility, dietary fiber content and bioactive potential by determining rutin and quercetin levels during processing. Moreover, technological quality and sensory acceptance were also evaluated. Breads made with 30% or 45% WGBF showed higher mineral and fiber contents compared to the control, while the formulations with RBF showed higher bioaccessibility. No changes were observed in the rutin levels of the dough before and after fermentation, but after baking, rutin and quercetin levels increased. The highest starch hydrolysis was found in the formulation containing 45% RBF. The formulations made with 30% RBF or 30% WGBF were well accepted by consumers. Our study shows interesting results, as few studies report the effect of processing on bioactive compounds.
... Similarly, phytic acid reduces bioavailability of divalent cations (Weaver and Kannan 2002). Several research studies reported that phytate inhibits absorption of iron, zinc, calcium, magnesium, and manganese (Hallberg et al. 1989;Reddy et al. 1996;Bohn et al. 2004;Phillippy 2006). Heat processing in combination with extrusion can either degrade or inactivate the heat labile compounds like phytates and hence can improve availability of iron and zinc to certain extent. ...
... The current results showed that copper is significantly increased in the liver after the addition of strain psm16, while in the kidney, after the addition of psm16 strain or commercial phytase, the level of copper is still in the normal range, but lower than in phytic acid group alone, and magnesium also shows the same change. In contrast to previous studies, the addition of phytic acid in white wheat bread can inhibit partial apparent magnesium absorption in the human body (Bohn et al., 2004). Various reports document the effect of phytase supplementation on copper metabolism in corn-soybean meal diets. ...
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Trace minerals are extremely important for balanced nutrition, growth, and development in animals and humans. Phytic acid chelation promotes the use of probiotics in nutrition. The phytic acid-degrading strain Lactococcus lactis psm16 was obtained from swine milk by enrichment culture and direct plate methods. In this study, we evaluated the effect of the strain psm16 on mineral element content in a mouse model. Mice were divided into four groups: basal diet, 1% phytic acid, 1% phytic acid + psm16, 1% phytic acid + 500 U/kg commercial phytase. Concentrations of acetic acid, propionic acid, butyric acid, and total short-chain fatty acids were significantly increased in the strain psm16 group compared to the phytic acid group. The concentrations of copper ( p = 0.021) and zinc ( p = 0.017) in liver, calcium ( p = 0.000), manganese ( p = 0.000), and zinc ( p = 0.000) in plasma and manganese ( p = 0.010) and zinc ( p = 0.022) in kidney were significantly increased in psm16 group, while copper ( p = 0.007) and magnesium ( p = 0.001) were significantly reduced. In conclusion, the addition of phytic acid-degrading bacteria psm16 into a diet including phytic acid can affect the content of trace elements in the liver, kidney, and plasma of mice, counteracting the harmful effects of phytic acid.
... It has been reported that phytic acid stops the absorption of iron, zinc, calcium, magnesium, and manganese [15,16]. Removal of phytic acid increases the bioavailability of many cations and provides nutritional benefits of meals to fish. ...
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Phytase, a key biocatalyst with multipurpose applied potentialities, and its significant relationship to contemporary industrial apprehensions provide unique physicochemical and catalytic attributes. Owing to the rising research advancement, the convergence of technologies fosters additional merits to this industrially relevant biocatalyst, i.e., phytase. Enriched with multipurpose characteristics, phytase holds a significant global market share expected to reach up to $590 million USD by 2024 compared to its share from $380 million USD in 2019. Major applications of phytase are in the pharmaceutical, food, and feed sectors. Growth performance, nutrient digestibility, and mineral availability are vital factors in aquaculture. The manufacturing cost of feed in aquaculture is about 50–80%. Fish meal is a rich protein source; however, plant-based proteins are preferred due to high price issues. Plant-based diets contain antinutritional factors, primarily phytate, and fishes are incapable of metabolizing phytate. About 1% phosphorus (P) is present in the fish meal, which if not digested by fish and remain undigested, causing water pollution. Phytate has unfavorable impacts on fish growth and body composition. Phytate binds with phosphorus in fishes to make phytate-phosphorus complex and make it unavailable for fishes. Phytate also forms complexes commonly with cations such as calcium, iron, copper, magnesium, and so on, limiting the bioavailability of minerals. Phytate forms a bond with trypsin and intervenes with available protein. Phytase enzyme emancipates inorganic phosphorus from phytate when supplemented with plant-based diets. Numerous varieties of stable phytases, handling ease, and resistant to high temperature are discussed herein. The maximum use of phytase in aquaculture nutrition extends to the necessities of economical feed and safety environment. Graphic Abstract
... Its absorption has been known to take place passively in the small intestine. Owing to the less permeability of Mg as compared to Ca, it is absorbed to a lesser extent in the human intestine (Lule et al., 2020) Moreover, the antinutrient factors (phytic acid) and certain other medications like antibiotics further hinder the Mg absorption (Bohn et al., 2004;Wolber et al., 2013). ...
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Kiwi fruit (Actinidia deliciosa) belongs to the family Actinidiaceae and genus Actinidia. It is one of the most commercialized fruits on the international front and is loaded with many nutrients including vitamins, minerals, phytochemicals, and its parts are well recognized for their medicinal and therapeutic properties against diseases associated with the cardiovascular system, diabetes, kidney problems, cancer, digestive disorders, bone, and eye problems. Being a significant source of phytochemicals including caffeic acid, gallic acid, syringic acid, salicylic acid, ferulic acid, and protocatechuic acid; it contributes to the major flavonoid and phenolic contents of kiwi fruit. Kiwi fruit and its components are known to exhibit numerous pharmacological properties include antidiabetic, anti‐tumor, anti‐inflammatory, anti‐ulcer, antioxidant activity, hypoglycemic, hypolipidemic effects, and many more. Besides these, kiwi fruit also finds its traditional application in the effective treatment of edema, hepatitis, kidney problems, rheumatoid arthralgia, and microbial infections. The fiber present in kiwi fruit favors its water retention capacity which further aids in decreasing the transit time and maintains gastrointestinal health of the individual. Investigations are also being done on the insulin and glucose balance, weight maintenance, and homeostatic balance to kiwi fruit consumption. The present review chiefly aims to establish a better understanding of the nutritional composition, pharmacological properties, health benefits, traditional utilization, and commercialization of kiwi; which helps to provide scientific evidence‐based recommendations to the consumers.
... Phytate are not digestible by non-ruminant animals as well as human beings as their digestive system lacks the enzyme to solubilize them. Hence, the undigested phytate in the small intestine negatively affect absorption of minerals and other nutrients [5]. It inhibits utilization of certain digestive enzymes in the intestinal tract of animals and human beings. ...
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The absorption of manganese from soy formula was studied in adult volunteers by extrinsic labeling of test meals with 54Mn, followed by whole-body retention measurements for approximately 30 d after intake. Eight subjects participated twice in each of the two studies, acting as his or her own control. Soy formula containing the native content of phytic acid was compared with a similar dephytinized formula: geometric mean manganese absorption increased 2.3-fold from 0.7% (range: 0.2-1.1%) to 1.6% (range: 1.0-7.2%) (P < 0.01) with the dephytinized formula. In addition, the effect of the ascorbic acid content of the phytic acid-containing formula was investigated. Manganese absorption was not influenced by an increase in the ascorbic acid from 625 mumol/L (110 mg/L) to 1250 mumol/L (220 mg/L): the geometric mean manganese absorption was 0.6% (range: 0.3-1.0%) and 0.6% (range: 0.3-1.1%), respectively. In conclusion, fractional manganese absorption was approximately doubled by the dephytinization of soy formula but was not influenced by an increase in the ascorbic acid content of a soy formula containing the native amount of phytic acid.
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During a 20 day period of high fiber consumption in the form of bread made partly from wheaten wholemeal, two men developed negative balances of calcium, magnesium, zinc and phosphorus due to increased fecal excretion of each element. The fecal losses correlated closely with fecal dry matter and phosphorus. Fecal dry matter, in turn, was directly proportional to fecal fiber excretion. Balances of nitrogen remained positive. Mineral elements were well-utilized by the same subjects during a 20 day period of white bread consumption.
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The effect of phytate on the solubility of some minerals (Mg2+, Ca2+, Fe3+, Cu2+ and Zn2+) has been investigated in vitro at 37°C, under pH conditions which may be encountered in the duodenum. The observed solubility trends as a function of phytate concentration and pH result from the formation of complexes having different stoichiometries and solubilities as the conditions are varied. Possible structures for these complexes are proposed. In view of the ever-increasing concern over cadmium toxicity and a recent report which indicates that intestinal absorption of Cd2+ is affected by phytate, this ion was included as part of this study.
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ABSTRACTA HPLC method was developed for separation and quantitative determination of inositol tri-, tetra-, penta-, and hexaphosphates. The method included extraction of inositol phosphates with HCI, separation of the inositol phosphates from the crude extract by ion-exchange chromatography, and ion-pair C18 reverse phase HPLC analysis using formic acid/methanol and tetrabutylammonium hydroxide in the mobile phase. The inositol 3–6 phosphates of raw and extruded bran, soy flour, and intestinal contents were determined by HPLC and compared to phytate determinations by two iron precipitation methods. Inositol 3–5 phosphates were found in extruded products and intestinal contents. The HPLC method was rapid and gave reproducible values, which differed from those obtained by the precipitation methods in some samples.
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The interactions of Mg(II), Co(II), Ni(II), and Zn(II) with phytic acid to form soluble complexes have been studied by calorimetry. The reactions were examined at metal ion:phytate mol ratios ranging from 1–6. The heats of reaction were endothermic over this range of mol ratios. Enthalpies were calculated in terms of cal mol−1 phytate. These enthalpies are a composite of a number of factors, among which are the heat of complex formation, the heat of dehyrdation of both the phytate and the various metal ions, the heats of ionization of the phytate, and the heat of hydration of protons released from the phytate. The enthalpies of complex formation of these metal cations with phytic acid are compared to those of two other metal cations, Mn(II) and Cu(II), which were studied under similar conditions. Based on the enthalpies, it is suggested that the order of affinity of these various metal cations for phytic acid is Cu(II) ≥ Zn(II) > Mn(II) > Mg(II) > Co(II) > Ni(II)In one instance, Mg(II), the heat of precipitation (which includes binding, solvation changes, etc.) to form the insoluble Mg(II)-phytate complex was determined. The reaction was endothermic and had an enthalpy of 12.9 kcal mol−1. This quantity is markedly different from the reported heats of precipitation reactions involving Cu(II), Zn(II), Mn(II), Ca(II), Co(II), and Ni(II) with phytate. From measurements of the Mg(II) concentration, it was calculated that 5.2 mol Mg(II) binds per mol of precipitated phytate.
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Fractional iron absorption from a breakfast meal was determined in Peruvian children employing stable iron isotopes as labels. Iron isotopic analysis was performed by the recently developed negative thermal ionization technique for high-precision iron isotope ratio measurements using FeF4 – ions. By increasing the ascorbic acid content of the standard breakfast meal as served within the Peruvian school-breakfast program from 27 mg to 70 mg, it was possible to increase the geometric mean fractional iron absorption significantly from 5.1% (range 1.6–13.5%) to 8.2% (range 3.1–25.8%). Fractional iron absorption was calculated according to isotope dilution principles and by considering the non-monoisotopic character of the used spikes.
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An Ultrafiltration (UF) based reactor system for continuous hydrolysis of proteins was developed to overcome limitations of the traditional batch process. A continuous stirred tank reactor was coupled to a hollow fiber module in a semiclosed loop configuration. Capacity of the reactor, defined as quantity of hydrolysate produced/time/weight of enzyme, was a sensitive function of enzyme concentration between 55 and 94% substrate conversion levels for the Pronase-Promine D system. Increasing flow rate also improved capacity, but substrate concentration and reactor volume had small effects on capacity within the levels of expected use. Productivity (defined as weight of hydrolysate/weight of enzyme) was at least 10-20 times greater for the continuous UF reactor than a batch reactor operating under otherwise identical conditions.
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Methods available for myoinositol phosphate measurement, effects of processing and role of myoinositol phosphates in human nutrition, including possible anticancer functions and other positive effects, will be discussed in contrast to the detrimental effects of myoinositol phosphates on mineral element bioavailability. The phytic acid content in diets will also be discussed.