Phytic acid calcium

As reviewed recently by Solomons W, many dietary and non-dietary factors may affect the bloavallablllty of zinc. Dietary factors are subdivided Into "Intrinsic factors" and "extrinsic factors". "Intrinsic factors" relate to the chemical nature of zinc Itself. "Extrinsic factors" Include non-heme Iron, ethyl-enedlamlnetetraacetlc acid (EDTA), dietary fiber, phytic acid, calcium, copper and specific foods such as cow s milk, cheese, coffee, eggs, celery and lemon which have been demonstrated to decrease zinc bloavallablllty as well as other factors which may Increase zinc utilization. 

The prediction of zinc bioavailability from complex food systems is not a simple matter. Animal bioassays and in vitro tests help us to identify factors that may enhance or inhibit zinc utilization from the diet. With simple model food systems, we can demonstrate the negative effects of phytic acid, calcium and other factors on zinc bioavailability. However, the interaction of these factors in complex food systems, and their effect on zinc status for man is not well understood at this time. 

To study the effect of phytic acid, calcium and protein in bread meals in various combination, on the zinc absorption in man. 

Sequestrants form complexes with metal ions, which accelerate oxidative degradation, and show synergistic effects with the a.m. antioxidants. - Phytic acid, calcium gluconate (- gluconic acid), - lactic acid and lactates, - tartaric acid and tartrates, - citric acid and citrates and - lecithin are such RR-based products. 

Proteins and Meals. Nutritional properties of the oilseed protein meals and their derived products are deterrnined by the amino acid compositions, content of biologically active proteins, and various nonprotein constituents found in the defatted meals. Phytic acid (3), present as salts in all four meals, is beheved to interfere with dietary absorption of minerals such as 2inc, calcium, and iron (67) (see Food toxicants, naturally occurring Mineral nutrients). ... 

Heretofore, no economical method for preparing pure phytic acid was known. The classical method was to dissolve calcium phytate in an acid such as hydrochloric acid, and then add a solution of a copper salt, such as copper sulfate to precipitate copper phytate. The latter was suspended in water and treated with hydrogen sulfide, which formed insoluble copper sulfide and released phytic acid to the solution. After removing the copper sulfide by filtration, the filtrate was concentrated to yield phytic acid as a syrup. 

The phytic acid in the form of a calcium phytate press cake may however be contacted with a cation exchange resin to replace the calcium with sodium to yield phytate sodium. 

For HS-I, with calcium intakes of about 1100 mg/day, no difference was observed in either apparent absorption or balance of calcium over the last 10 of 15 days when the phytate intake was 0.2 or 2.0 g/day. The molar ratio of phytate/calcium was either 0.01 or 0.1 in HS-I. In HS-II the calcium intake was lower, about 740 mg/day, but the same across three levels of phytic acid, 0.5, 1.7 and 2.9 g/day. The phytate/calcium molar ratios were 0.04, 0.14 and 0.24. Apparent absorption of calcium for the 15-day diet treatment period became progressively less as the molar ratio of phytate/calcium increased, to the extent that 6 of 12 individuals excreted more calcium in the feces than they consumed when the mean ratio was 0.24. About 200 mg of calcium was excreted daily in the urine by... 

Table V shows the composition of the liquid meals for this study. As in the previous study, two levels each of cottage cheese and beef were fed to the subjects. In addition, 45 g of protein from soy isolate was also fed. The phytic acid content of this meal was 126 mg. A basal diet containing all nutrients except protein was also included in this study. It was necessary to reduce the fat content of the basal diet for palatability the total energy for this meal only was 250 kcal. In this study, the calcium and phosphorus levels of each meal were equalized across all levels and sources of protein. Levels of other meal components were maintained as constant as possible and are shown at the bottom of Table V.

Veum, T. L., Ledoux, D. R., Bollinger, D. W., Raboy, V., and Cook, A. (2002). Low-phytic acid barley improves calcium and phosphorus utilization and growth performance in growing pigs. J. Anim. Sci. 80, 2663-2670. 

Much of the current research has centered upon the role of phytic acid on zinc and iron bioavailability (110-124). Work performed at the authors institution with several different types of soy foods suggests that phytic acid is a major factor affecting availability of zinc from foods derived from the legume (110-114). In addition, it appears that endogenous zinc in high-phytate foods may be a limiting factor in optimal utilization of these foods for man. We have found that fortification of soy foods (under proper conditions) with zinc, iron, magnesium, or calcium results in excellent... 

Phytic acid, although restricted to a more narrow range of food products, mainly grains, complexes a broader spectrum of minerals than does oxalic acid. Decreased availability of P is probably the most widely recognized result of excessive intakes of phytic acid, yet Ca. Cu, Zn, Fe. and Mn are also complexed and rendered unavailable hy this compound. High intakes of both calcium and vitamin D help to offset ihe deleterious effects of oxalates. 

Ravindran (1991) estimated the protein content of ragi to be 9.8%, that of calcium, oxalate, and phytic acid to be 0.24%, 0.44 mg%, and 0.48%, respectively. Hadimani and Malleshi (1993) compared the protein, lipid, ash, calcium, phosphorus, and dietary fiber contents of seven native and milled millets. The protein content of ragi milled flour decreased by 61%... 

Fig. 21. Example of results analysed using the site-blocking mechanism, eqn. (196), for the growth of calcium hyroxyapatite (HAP) on HAP seeds in the presence of phytic acid. (Reproduced from ref. 58 by courtesy of Academic Press, Inc.)...

The ash content of soybeans is relatively high, close to 5 percent. The ash and major mineral levels in soybeans are listed in Table 5-7. Potassium and phosphorus are the elements present in greatest abundance. About 70 to 80 percent of the phosphorus in soybeans is present in the form of phytic acid, the phosphoric acid ester of inositol (Figure 5-5). Phytin is the calcium-magnesium-potassium salt of inositol hexaphosphoric acid or phytic acid. The phytates are important because of their effect on protein solubility and because they may interfere with absorption of calcium from the diet. Phytic acid is present in many foods of plant origin. 

The Interest In the chemical interrelationships of phytate Initially centered around Its complexatlon with calcium and subsequent effect on the availability of calcium (33). This led to the classical studies by Hoff-Jorgenson (34). He determined eight of the twelve dissociation constants of phytic acid and using these data calculated thj solubilij products of penta-calclum phytate as between 10 and 10. A decade later with the use of neutralization curves and conductivity measurements it was concluded that phytic acid contained 6 strong acid groups which were completely dissociated in solution (pk = 1.84), 2 weak acid functions (pk = 6.3) and 4 very weak acid protons (pk = 9.7) (M). 

Our work with soy products indicates that extrinsic zinc is more available than intrinsic zinc. The intrinsic and extrinsic zinc pools do not completely mix in all soy products. Phytic acid is an inhibitor of zinc bioavailability and this inhibition is aggravated by higher levels of dietary calcium and perhaps magnesium. Neutralization of soy isolates and concentates, with subsequent drying, reduces zinc utilization for rats. 

In animal experiments it has been shown that a high calcium content in combination with the phytic acid in whole flour bread will decrease the zinc absorption (10), When adding milk and milk products to the whole flour bread in Dr. Sandstr0ms experiments the same positive effect was seen from the protein despite of the higher calcium content (Table III). 

Interaction between zinc and calcium has been demonstrated In several animal studies (l- ). It has been shown that calcium antagonizes the biological effects of zinc and that calcium reduces the availability of zinc for absorption. This decrease In zinc absorption resulted In severe malnutrition and parakeratosis (1.-7.) Several studies have conclusively shown that the calclum-zlnc antagonism studied In animals Is due to excess phytic acid In the diet (, 9). However, In the absence of phytic acid, excess dietary calcium per se has also been shown to decrease the Intestinal absorption and the retention of zinc In rats (10). This Inhibitory effect on zinc absorption. Induced by calcium, was further enhanced by the addition of phosphorus to the high calcium Intake (11). 

These studies, as well as additional studies carried out In this Research Unit, have shown that Increasing the calcium Intake up to 2000 mg per day does not affect the excretions or retention of zinc In man. These observations are In contrast to results obtained In animal studies (10) which have shown that a high calcium Intake per se. In the absence of phytic acid, can decrease... 

Phytates found in cereals, legumes, nuts and oil seeds form complexes with minerals, the mineral-phytate complexes in decreasing order of stability being zinc > copper > nickel > cobalt > manganese > calcium. Thus, zinc is affected most. An increase in pH results in phytic acid becoming more ionized and initiates binding to cations. 

Plant foods contain relatively large amounts of inositol phosphates, including the hexaphosphate, phytic acid. Phytate chelates minerals, such as calcium, zinc, and magnesium, forming insoluble complexes that are not absorbed. However, both intestinal phosphatases and endogenous phosphatases (phytase) in many foods dephosphorylate a significant proportion of dietary phytate. The inositol released can be absorbed and utilized for phosphatidylinositol synthesis. 

Both the glycolipids and the phospholipids of corn have lower percentages of linolenic acid (18 3) and are more saturated than those in the soybean. In general, cmde corn and soybean lecithins are equal in linoleic acid (18 2) content, but lino-leic acid in corn varies from 42% to 70% depending on the variety of corn. Phytic acid, 88% of which is in the com germ, is extracted as part of the lecithin fraction (32, 37). Elimination of phytic acid in com is desirable because it binds zinc, magnesium, and calcium. 

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