High-phytate foods, such as grains, nuts and legumes,
can raise the risk of iron and zinc deficiency.
As a countermeasure, strategies such as soaking, sprouting and fermentation are often employed.
For those who eat meat regularly, deficiencies caused by phytic acid are not a concern.
The mineral content of legumes is generally high,
but the bioavailability is poor due to the presence of phytate,
which is a main inhibitor of Fe and Zn absorption.
Some legumes also contain considerable amounts of Fe-binding polyphenols inhibiting Fe absorption.
Furthermore, soya protein 'per se'(en elles-mêmes) has an inhibiting effect on Fe absorption.
Efficient removal of phytate, and probably also polyphenols,
can be obtained by enzymatic degradation during food processing,
either by increasing the activity of the naturally occurring plant phytases and polyphenol degrading enzymes,
or by addition of enzyme preparations.
Biological food processing techniques that increase the activity of the native enzymes
are soaking, germination, hydrothermal treatment and fermentation.
La transformation des aliments peut être optimisée pour atteindre une dégradation maximale du phytate
à condition de connaître les conditions optimales pour l'activité de la phytase dans la plante.
In contrast to cereals, some legumes have highest phytate degradation at neutral or alkaline pH.
Addition of microbial enzyme preparations seems to be the most efficient for complete degradation during processing.
Fe and Zn absorption have been shown to be low from legume-based diets.
It has also been demonstrated that nutritional Fe deficiency
reaches its greatest prevalence in populations subsisting on cereal- and legume-based diets.
However, in a balanced diet containing animal protein a high intake of legumes is not considered a risk in terms of mineral supply.
Furthermore, once phytate, and in certain legumes polyphenols, is degraded,
legumes would become good sources of Fe and Zn as the content of these minerals is high.
ncbi.nlm.nih.gov/pubmed/12498628
Food sources of phytic acid (g/100g)
| Food | [% minimum dry] | [% maximum dry] |
|---|---|---|
| Brazil nuts | 1.97 | 6.34 |
| Sesame seeds flour | 5.36 | 5.36 |
| Pumpkin seed | 4.3 | 4.3 |
| Almonds | 1.35 | 3.22 |
| Tofu | 1.46 | 2.90 |
| Linseed | 2.15 | 2.78 |
| Oat Meal | 0.89 | 2.40 |
| Beans, pinto | 2.38 | 2.38 |
| Soybeans | 1.00 | 2.22 |
| Maize (Corn) | 0.75 | 2.22 |
| Soy protein concentrate | 1.24 | 2.17 |
| Peanut | 0.95 | 1.76 |
| Soy beverage | 1.24 | 1.24 |
| Chia seeds | 0.96 | 1.16 |
| Coconut | 0.36 | 0.36 |
| Hazelnut | 0.65 | 0.65 |
| Walnut | 0.98 | 0.98 |
| Oat | 0.42 | 1.16 |
| Wheat | 0.39 | 1.35 |
| Wheat flour | 0.25 | 1.37 |
| Wheat germ | 0.08 | 1.14 |
| Whole wheat bread | 0.43 | 1.05 |
| Buckwheat | 1.00 | 1.00 |
| Brown rice | 0.84 | 0.99 |
| Polished rice | 0.14 | 0.60 |
| Chickpeas | 0.56 | 0.56 |
| Lentils | 0.44 | 0.50 |
| New potato | 0.18 | 0.34 |
| Spinach | 0.22 | NR |
| Avocado fruit | 0.51 | 0.51 |
Chestnuts(castane) contain 47 mg of phytic acid for 100g.
Oak acorn of Quercus ilex contains 127 mg of phytic acid for 100g.
en.wikipedia.org/wiki/Phytic_acid
Whole wheat bread is an important source of minerals
but also contains considerable amounts of phytic acid,
which is known to impair their absorption.
An in vitro trial was performed to assess the effect of a moderate drop of the dough pH (around 5.5)
by way of sourdough fermentation or by exogenous organic acid addition on phytate hydrolysis.
It was shown that a slight acidification of the dough (pH 5.5)
with either sourdough or lactic acid addition
allowed a significant phytate breakdown
(70% of the initial flour content compared to 40% without any leavening agent or acidification).
This result highlights the predominance of wheat phytase activity
over sourdough microflora phytase activity
during moderate sourdough fermentation
and shows that a slight drop of the pH (pH value around 5.5)
is sufficient to reduce significantly the phytate content of a wholemeal flour.
Mg "bioaccessibility"of whole wheat dough was improved
by direct solubilization of the cation and by phytate hydrolysis.
Lactic acid fermentation of cereal flours
resulted in a 100 (rye), 95-100 (wheat), and 39-47% (oat) reduction in phytate content within 24 h.
The extent of phytate degradation was shown to be independent from the lactic acid bacteria strain used for fermentation.
However, phytate degradation during cereal dough fermentation
was positively correlated with endogenous plant phytase activity
(rye, 6750 mU g(-1); wheat, 2930 mU g(-1); and oat, 23 mU g(-1)),
and heat inactivation of the endogenous cereal phytases
prior to lactic acid fermentation resulted in a complete loss of phytate degradation.
Phytate degradation was restored after addition of a purified phytase to the liquid dough.
Incubation of the cereal flours in buffered solutions
resulted in a pH-dependent phytate degradation.
The optimum of phytate degradation was shown to be around pH 5.5.
Studies on phytase production of 50 lactic acid bacteria strains,
previously isolated from sourdoughs,
did not result in a significant production of intra- as well as extracellular phytase activity.
Therefore, lactic acid bacteria do not participate directly in phytate degradation
but provide favorable conditions for the endogenous cereal phytase activity
by lowering the pH value.
High-phytate foods, such as grains, nuts and legumes, can raise the risk of iron and zinc deficiency.
As a countermeasure, strategies such as soaking, sprouting and fermentation are often employed.
For those who eat meat regularly, deficiencies caused by phytic acid are not a concern.
On the contrary, consuming high-phytate foods as part of a balanced diet has numerous benefits.
In most cases, these benefits outweigh any negative effects on mineral absorption.