S330
Review
Phytate in foods and significance for humans:
Food sources, intake, processing, bioavailability,
protective role and analysis
Ulrich Schlemmer1, Wenche Frølich2, Rafel M. Prieto3, 4 and Felix Grases3, 4
1 Department of Physiology and Biochemistry of Nutrition, Max Rubner-Institut, Federal Research Institute
of Nutrition and Food, Karlsruhe, Germany
2 University of Stavanger, Norwegian School of Hotel Management, Jar, Norway
3 Laboratory of Renal Lithiasis Research, University Institute of Health Sciences Research (IUNICS),
University of Balearic Islands Ctra, Palma de Mallorca
4 CIBER Fisiopatolog
a Obesidad y Nutricin (CB06/03), Instituto de Salud Carlos III, Spain
The article gives an overview of phytic acid in food and of its significance for human nutrition. It
summarises phytate sources in foods and discusses problems of phytic acid/phytate contents of food
tables. Data on phytic acid intake are evaluated and daily phytic acid intake depending on food habits
is assessed. Degradation of phytate during gastro-intestinal passage is summarised, the mechanism of
phytate interacting with minerals and trace elements in the gastro-intestinal chyme described and the
pathway of inositol phosphate hydrolysis in the gut presented. The present knowledge of phytate
absorption is summarised and discussed. Effects of phytate on mineral and trace element bioavailabil-
ity are reported and phytate degradation during processing and storage is described. Beneficial activ-
ities of dietary phytate such as its effects on calcification and kidney stone formation and on lowering
blood glucose and lipids are reported. The antioxidative property of phytic acid and its potentional
anticancerogenic activities are briefly surveyed. Development of the analysis of phytic acid and other
inositol phosphates is described, problems of inositol phosphate determination and detection dis-
cussed and the need for standardisation of phytic acid analysis in foods argued.
Keywords:Absorption / Antioxidant / Degradation / Inositol phosphates / Phytic acid /
Received:March 7, 2009; revised: May 25, 2009; accepted: May 31, 2009
1 Introduction
The discovery of phytate dates from 1855 to 1856 when
Hartig first reported small round particles in various plant
seeds similar in size to potato starch grains [1, 2]. Using the
iodine test he showed that the particles were free of starch
and concluded that they must contain reserve nutrients for
the germination of seeds. Later it was discovered that the
isolated particles were rich in phosphorous, calcium and
magnesium but neither contained proteins nor lipids [3].
The name
,
phytin’ was created by virtue of the fact that this
substance is of plant origin, having been detected neither in
meat nor in dairy products, and it originally described the
classical calcium–magnesium phytate deposits of plant
seeds [3]. Winterstein [4], Schulze and Winterstein [5] and
Posternak [6] showed that hydrolysing phytin by hydro-
chloric acid liberated phosphoric acid and inositol. To
explain the high phosphorous, calcium and magnesium
contents of phytin, paired phosphoric acids were discussed
as possible structures [7, 8]. Other molecular structures,
however, were also under controversial debate for many
years [8, 9]. In 1914, Anderson [10] presented the molecu-
lar structure of myo-inositol-1,2,3,4,5,6-hexakis dihydro-
gen phosphate, also called phytic acid (Fig. 1), which is still
valid and was confirmed by various modern analytical
methods [11–13].
Phytate, the salt of phytic acid, is widely distributed in
the plant kingdom. It serves as a storage form of phospho-
Correspondence: Dr. U. Schlemmer, Department of Physiology and
Biochemistry of Nutrition, Max Rubner-Institut, Federal Research In-
stitute of Nutrition and Food, Haid-und-Neu-Straße 9, 76131 Karls-
ruhe, Germany
E-mail: ulrich.schlemmer@mri.bund.de;
Schlemmer.van-Ruiten@t-online.de
Fax: +49-721-6625-404
Abbreviations: HAP, hydroxyapatite; ICP, inductively coupled plas-
ma; PAR, 4-(2-pyridylazo) resorcinol; TBARS, thiobarbituric acid re-
acting substances
i 2009WILEY-VCH Verlag GmbH &Co. KGaA,Weinheim www.mnf-journal.com
DOI 10.1002/mnfr.200900099 Mol. Nutr. Food Res. 2009, 53, S330–S375

Mol. Nutr. Food Res. 2009, 53, S330–S375
rous and minerals and contains l75% of total phosphorous
of the kernels [14]. Other parts of plants such as roots,
tubers and turions, however, are very low in phytate (l0.1%
dw) [15]. Besides phytate, other inositol phosphates such as
inositol pentaphosphates and inositol tertraphosphates are
also present in seeds, however, to a much lower extent
(a15%) [16]. During the germination of seeds, phytate is
hydrolysed [17, 18] and phosphate along with minerals
such as calcium and magnesium becomes susceptible for
germination and development of the seedlings, explaining
its significant role in plant metabolism.
Phytate is predominantly present in unprocessed food, but
can be degraded during processing, so a broad range of inosi-
tol phosphates may be consumed. It has been estimated that
the daily intake of phytate and other inositol phosphates on
the basis ofWestern style diets varies froml0.3 to 2.6 g [19]
and in a global range from 0.180 to 4.569 g [20], strongly
depending on the diet selected; low in normal Western diets
and high in vegetarian diets. Under heat treatment up to
l1008C (home cooking, roasting, pressure cooking, etc.)
phytate is quite stable [21, 22]while foodprocessingwith the
aid of phytasesmay result in strongphytate hydrolysis [23].
For decades phytate has been regarded as an antinutrient,
as, during gastro-intestinal passage, it may inhibit the
absorption of some essential trace elements and minerals,
which under certain dietary circumstances may lead to cal-
cium, iron and zinc deficiencies [24–29]. Thus, intensive
research has been carried out to remove phytate from food
by proper processing, to improve the bioavailability and to
avoid deficiencies of essential trace elements and minerals.
In the last 20 years, however, beneficial properties of phy-
tate have been observed and antioxidant [30] and anticancer
activities [31] were reported. Inhibition of calcium salt
crystallisation and prevention of renal stone formation
through dietary phytate were described [32]. Reduction of
starch digestion along with slowing down of the glycemic
index of foods [33, 34] have also been reported, as well as
positive effects on blood glucose and blood cholesterol [35,
36]. These findings have revived discussions about the sig-
nificance of phytate and other inositol phosphates in human
nutrition and for human health.
Of central interest therefore is to understand how phytate
exerts its beneficial effects in organs and cells, what the fate
of phytate is during the digestion in the gut and how phytate
and its degradations products can be absorbed.
Under physiological pH (l6–7) phytate is highly nega-
tively charged [13] (Fig. 1) and as no adequate carriers have
been detected by now, it has long been assumed that phytate
cannot cross the lipid bilayer of plasma membranes and in
consequence, its absorption in the gut has been considered
rather improbable. However, recent studies in humans and
rats have shown increasing levels of phytate in plasma and
enhanced urinary phytate excretion after application of
sodium phytate [37, 38]. Studies with radioactive labelled
phytate in rats also provided some evidence for the absorp-
tion of phytate or at least of parts of its degradation products
[39, 40]. Cellular uptake studies with MCF-7 cells also pro-
vide evidence of phytate absorption [41] and recent experi-
ments with HeLa show that cellular uptake of phytate might
occur via pinocytosis [42]. Moreover, the great number of
studies showing anticancer activity of phytate in skin, lung,
liver, mammary, prostate, soft tissue, etc. also suggest that
phytate or phytate degradation products have to be absorbed
to a certain extent, even though the absorption mechanism
still remains to be clarified [41].
This review gives an overview of the main dietary food
sources of phytate and the estimated daily intake. It
describes the degradation of phytate during gastro-intesti-
nal digestion and the passage throughout the gut and dis-
cusses the present knowledge of cellular uptake, absorption
and bioavailability of phytate and lower phosphorylated
inositol phosphates. Moreover, it surveys the adverse and
beneficial activities of phytate and reports the development
and progress made in the analysis of phytate and other ino-
sitol phosphates in food.
S331
i 2009WILEY-VCH Verlag GmbH &Co. KGaA,Weinheim www.mnf-journal.com
Figure 1. myo-inositol-1,2,3,4,5,6-hexakis phosphate at
pH 6–7. Under physiological conditions the negative charges
are counterbalanced most likely by sodium ions or by other
cations. Conformation: 5 axial/1 equatorial (modified to Emsey
and Niazi [11]).
Table 1. Sources of dietary energy consumption according to
the FAO (kcal/capita/day, 2001–2003)a)
Sources Developed
countries
% Developing
countries
%
Fruits and vegetables 308 9.3 295 11.1
Cereals 1020 30.7 1391 52.4
Pulses 286 8.6 198 7.5
Sugar 427 12.9 194 7.3
Animal products 712 21.5 311 11.7
Oils and fats 566 17.1 267 10.1
Total 3319 100.0 2656 100.0
a) Adapted from [43].