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   The role of phytic acid in legumes: antinutrient or beneficial
   function?
   J Physiol Biochem 2000 Sep;56(3):283-94
   Urbano G. Lopez-Jurado M. Aranda P. Vidal-Valverde C. Tenorio E.
   Porres J.
   This review describes the present state of knowledge about phytic acid
   (phytate), which is often present in legume seeds. The antinutritional
   effects of phytic acid primarily relate to the strong chelating
   associated with its six reactive phosphate groups. Its ability to
   complex with proteins and particularly with minerals has been a
   subject of investigation from chemical and nutritional viewpoints. The
   hydrolysis of phytate into inositol and phosphates or phosphoric acid
   occurs as a result of phytase or nonenzymatic cleavage. Enzymes
   capable of hydrolysing phytates are widely distributed in
   micro-organisms, plants and animals. Phytases act in a stepwise manner
   to catalyse the hydrolysis of phytic acid. To reduce or eliminate the
   chelating ability of phytate, dephosphorylation of hexa- and
   penta-phosphate forms is essential since a high degree of
   phosphorylation is necessary to bind minerals. There are several
   methods of decreasing the inhibitory effect of phytic acid on mineral
   absorption (cooking, germination, fermentation, soaking, autolysis).
   Nevertheless, inositol hexaphosphate is receiving increased attention
   owing to its role in cancer prevention and/or therapy and its
   hypocholesterolaemic effect.

   Dietary factors influencing zinc absorption.
   J Nutr 2000 May;130(5S Suppl):1378S-83S
   Lonnerdal B. Iino M. Shears SB. Woodcock EA. Arthur JF. Matkovich SJ.
   Urbano G. Lopez-Jurado M. Aranda P. Vidal-Valverde C. Tenorio E.
   Porres J.
   Marginal zinc deficiency and suboptimal zinc status have been
   recognized in many groups of the population in both less developed and
   industrialized countries. Although the cause in some cases may be
   inadequate dietary intake of zinc, inhibitors of zinc absorption are
   most likely the most common causative factor. Phytate, which is
   present in staple foods like cereals, corn and rice, has a strong
   negative effect on zinc absorption from composite meals. Inositol
   hexaphosphates and pentaphosphates are the phytate forms that exert
   these negative effects, whereas the lower phosphates have no or little
   effect on zinc absorption. The removal or reduction of phytate by
   enzyme (phytase) treatment, precipitation methods, germination,
   fermentation or plant breeding/genetic engineering markedly improves
   zinc absorption. Iron can have a negative effect on zinc absorption,
   if given together in a supplement, whereas no effect is observed when
   the same amounts are present in a meal as fortificants. Cadmium, which
   is increasing in the environment, also inhibits zinc absorption. The
   amount of protein in a meal has a positive effect on zinc absorption,
   but individual proteins may act differently; e.g., casein has a modest
   inhibitory effect of zinc absorption compared with other protein
   sources. Amino acids, such as histidine and methionine, and other
   low-molecular-weight ions, such as EDTA and organic acids (e.g.,
   citrate), are known to have a positive effect on zinc absorption and
   have been used for zinc supplements. Knowledge about dietary factors
   that inhibit zinc absorption and about ways to overcome or remove
   these factors is essential when designing strategies to improve the
   zinc nutrition of vulnerable groups.
   


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