Dietary Phytate Research Articles

Effect of age and dietary phytate on the availability of phytate and minerals in rats.

(1983). Effect of Age and Dietary Phytate on the Availability of Phytate and Minerals in Rats. Agricultural and Biological Chemistry: Vol. 47, No. 11, pp. 2641-2644.

The influence of four dietary proteins and sodium phytate on the metabolism of cholesterol and the lipoproteins in rat

The hypocholesterolemic effect of dietary proteins could not be related to their vegetal or animal origin and seemed correlated to their different amino acids proportions. Comparing rats fed soy protein diet to those fed casein diet for 45 days, we observed a decrease of serum HDL cholesterol levels. Furthermore sequential centrifugation showed a decrease of HDL2–3 fraction and especially apolipoprotein E in the serum of soy protein fed rats. The sodium phytate, added to the diet, did not change the metabolism of sterols.

Feed digestibility and mineral balance of the diet of young mice kept in mouse cages inside or outside an isolator, using varied concentrations of sodium phytate.

Young male mice of the C3H inbred strain were kept inside or outside a Trexler vinyl isolator and fed on three autoclaved purified diets which contained 0%, 1% or 5% sodium phytate. The feed N efficiency, the apparent digestibility of gross components of the diet, the balances of N, Ca, Mg and P, and the ash, Ca, Mg and P contents of bone were investigated for each group of mice. No significant differences in these parameters were found with respect to the location of the mouse cages inside or outside an isolator. Mice fed on 5% phytate diet, as compared with mice fed on 0% or 1% phytate diet, had a higher apparent digestibility of crude fat, and a lower apparent digestibility and retention rate of Mg. Urinary excretion and apparent digestibility of P in mice fed on 5% phytate diet were higher than in other groups of mice.

Phytate content of foods: Effect on dietary zinc bioavailability

The phytate content of several foods is presented. Published zinc values were used to calculate phytate:zinc molar ratios. These ratios can be used to estimate the relative risk of having an inadequate intake of zinc. They may be used in planning menus to select the combination of foods that will supply the most available zinc to the daily diet. On the basis of animal experiments to date, a daily phytate:zinc molar ratio of 10 or less is thought to be acceptable in providing adequate dietary zinc, and daily ratios consistently above 20 may jeopardize zinc status. Many factors other than the daily dietary phytate:zinc molar ratio influence zinc nutriture, but the ratio concept is a tool which may contribute to a more accurate assessment of zinc status.

Iron Availability and Absorption in Rats Fed Sodium Phytate

Effects of dietary sodium phytate on iron availability and absorption in rats were assessed in two experiments. In the first experiment, iron-deficient rats were switched to diets containing variable levels of added sodium phytate and variable levels of iron as ferrous sulfate. Iron availability was evaluated by measuring hemoglobin regeneration after 2 weeks of feeding these diets. In the second experiment, both iron-adequate and iron-deficient rats were force-fed a slurry containing an iron-deficient diet, 59Fe and sodium phytate. Iron absorption was assessed by measuring the percentage of the 59Fe dose retained by the rats after 9 days. The results of the first experiment indicated that levels of dietary phytate up to 4% of the diet do not impair hemoglobin regeneration by anemic rats. The results of the second experiment indicated that sodium phytate does not affect iron absorption differently in iron-adequate rats compared to iron-deficient rats. It is suggested that conflicting results in the literature on effects of phytate on iron absorption may be explained by differences in experimental conditions or by the presence in the diet of some inhibitory component besides phytate, possibly dietary fiber.iron bioavailability dietary phytate

Metabolism of 14C-Phytate in Rats: Effect of Low and High Dietary Calcium Intakes

The purpose of this study was to explore in rats the in vivo metabolism of phytate, using [U-14C]phytate and to assess the effects of calcium intake on phytate and myo-inositol metabolism. Labeled phytate was prepared from wheat following injection of the plants at the milk stage with [U-14C]myo-inositol. Groups of 30-day-old male rats were adapted for at least 6 weeks either to a low-calcium (2.9 mM/100 g dry diet) or a high-calcium (30.6 mM/100 g dry diet) cereal-based diet. They were then transferred to metabolic cages, continued on their respective diets and given an oral dose of [14C]phytate or [14C]myo-inositol. Appearance of radioactivity in expired air, feces and urine was monitored for 48 hours; the rats were then killed for determination of 14C-activity in liver, kidneys, blood and femur. The high-calcium diet significantly increased the output of radioactivity in feces (54% of dose) and reduced the appearance of radioactivity in expired air (25% dose) and in body tissues following 14C-phytate administration. The high-calcium intake did not affect the fate of [14C]myo-inositol (96% of dose). These results suggest that phytate or a derivative(s) is almost quantitatively absorbed (94% of dose) when calcium intake is low (Ca/P molar ratio; 0.21) and it is extensively oxidized to CO2 (60% of dose). Thus, a high-calcium intake (Ca/P molar ratio; 2.24) inhibits the utilization of [14C]phytate. Hence, it is suggested that the impact of dietary phytate on trace mineral bioavailability will depend upon the presence of factors, including excess calcium, that alter the absorption and utilization of phytate.

Studies on the phytate: zinc molar contents in diets as a determinant of Zn availability to young rats

1. Studies were carried out in vitro to examine the effects of phytate on the solubility of the trace elements zinc, copper and manganese. Appropriate volumes of a solution of sodium phytate were added to a mineral solution to achieve phytate: Zn values of from 0 : 1 to 45 : 1. In a second series the same values for phytate: Zn were achieved by varying the amount of added Zn at a fixed phytate concentration. 2. In both experiments greater than 85% of the Zn was rendered insoluble at pH 6.5 even at the lowest value for phytate: Zn (5 : 1). The effect of phytate on Zn solubility was greater than effects on Cu or Mn. 3. In a dietary study, rats were offered a semi-synthetic egg-albumin-based diet with added phytate. Two series of diets were prepared, the first had a constant Zn content (18.5 mg Zn/kg) and the amount of sodium phytate varied so as to achieve values for phytate: Zn of from 0 : 1 to 40 : 1 (series 1). In the second series, the same values for phytate: Zn were achieved by adding a fixed amount of phytate (7.4 g phytic acid/kg) while the amount of Zn was varied (series 2). 4. Dietary phytate caused significant reductions in growth rates, plasma Zn concentrations and hair Zn concentrations and greying of the coat at values for phytate: Zn of 15 : 1, 10 : 1, 15 : 1 and 15 : 1, respectively. 5. While phytate was apparently slightly more effective in reducing Zn status when phytate: Zn values were achieved at the lower absolute levels of phytate and zn (series 1 diets), the differences at equivalent phytate: Zn values were small. It was concluded that phytate: Zn values can be used as an indicator of Zn availability from phytate-rich diets. 6. Rats offered three diets containing soya-bean-based textured-vegetable-protein (TVP) exhibited low rates of weight gain compared with rats offered an egg-albumen-based diet of similar Zn content (14.5 mg Zn/kg). Additional Zn supplied in drinking-water (25 mg Zn//l) was without effect on rats consuming the egg-albumin diet but significantly improved the weight gain of rats on the TVP diets. 7. It was concluded that phytate naturally present in TVP behaves similarly to phytate added to an otherwise phytate-free diet and that the reduced availability of Zn in TVP diets can be accounted for entirely by their phytate contents.

A possible relationship between high-extraction cereal and rickets and osteomalacia.

The evidence of the present study suggests a strong and possibly causal relationship between high-extraction cereal and rickets and osteomalacia. It seems likely that this occurs when vitamin-D status is border-line. The rachitogenic component of high-extraction cereal remains to be identified; dietary phytate now seems unlikely and phytate-derived polyphosphate esters or dietary phosphorus may be incriminated. The present study strongly indicates that Mellanby's original suggestion of an "anti-calcifying substance" in high-extraction cereal remains valid.

The effects of phytate on intestinal absorption and secretion of zinc, and whole-body retention of Zn, copper, iron and manganese in rats.

1. The inclusion of phytate (10 g/kg) in a purified diet containing zinc (15 mg/kg) fed to young male rats significantly reduced growth rate and food intake, and promoted a cyclic pattern of food intake characteristic of an uncomplicated Zn deficiency. The decreased growth rate could be accounted for by the reduced food consumption. 2. Rats maintained on a Zn-deficient diet (0.5 mg Zn/kg) were found to have a cyclic pattern of food intake and a very slight weight gain. The addition of phytate (10 g/kg) to the Zn-deficient diet promoted a net loss of mean body-weight. 3. Rats maintained on the Zn-supplemented diet containing phytate excreted significantly more Zn in their faeces than either pair-fed or ad lib.-fed control rats. Rats given the Zn-deficient diet supplemented with phytate excreted more Zn in their faeces than Zn-deficient control rats. 4. Dietary phytate significantly reduced the average daily accumulation (mug/d) and whole-body retention (relative to dietary intake) of iron, copper, manganese and Zn, whether or not the diet was supplemented with Zn. 5. The addition of phytate to the lumen fluid of ligated loops of rat duodenum maintained in situ significantly inhibited 65Zn absorption, compared with the control systems without added phytate. 6. Other studies using ligated duodenal and ileal loops indicated that Zn is secreted into the gut lumen and approximately one-third of this is normally reabsorbed. Recycling of endogenous Zn may be a significant process in the over-all body economy of this trace element. 7. The absorption of 65Zn added to the diet was significantly reduced by dietary phytate. Dietary phytate also reduced the biological half-life of body 65Zn from 61 to 211 h post-administration, possibly by inhibiting reabsorption of endogenous 65Zn and thus promoting a more rapid loss from the body.

Effect of Phytate on Iron Absorption in the Rat

Hemoglobin regeneration was studied in groups of anemic rats fed purified diets containing 10 or 20 ppm of iron in which either 45 or 75% of the phosphorus was replaced with phytate phosphorus. The results were compared with those obtained with control animals receiving phytate-free diets. In the groups receiving 20 ppm of iron, hemoglobin regeneration was more rapid than in the groups given 10 ppm. However, at either level of iron, dietary phytate had no effect on iron absorption as measured by total hemoglobin regeneration.

Dietary phytate as a possible cause of magnesium deficiency.

Dietary phytate as a possible cause of magnesium deficiency.

Effect of dietary phytate on faecal absorption of radioactive ferric chloride.

IT has been stated that diets with high phosphate, phytate and low calcium content affect iron absorption by precipitating the iron as an insoluble iron phytate or phosphate; and that this might be a factor in the etiology of the widespread and severe iron-deficient anaemias of the tropics1–6. It is known that bulk has a deleterious effect on iron absorption.

The role of vitamin D and intestinal phytase in the prevention of rickets in rats on cereal diets

A study with rats of the role played by vitamin D in overcoming the rachitogenic properties of high-Ca phytic acid containing diets has shown that phytic acid in a low-Ca cereal ration was hydrolyzed almost completely even when vitamin D was absent. On the other hand, when the Ca content of the ration was increased, the hydrolysis of phytate was decreased. Under these conditions the addition of vitamin D increased the hydrolysis. The phytase and alkaline phosphatase activity of fecal and intestinal extracts from rats, whether they were fed cereal or noncereal, rachitogenic or nonrachitogenic rations, was always increased when vitamin D was given. However, no consistent correlation in a quantitative sense was found between the degree of hydrolysis of dietary phytate and enzyme activity, nor with the severity of rickets. The increased hydrolysis of phytic acid which is effected by the addition of vitamin D to high-Ca cereal diets did not liberate sufficient P in the inorganic form to account by itself for the prevention of rickets. Although less phytate was hydrolyzed by rachitic rats, the inorganic P in the feces was increased due to a decrease in its absorption. It therefore appears that the antirachitic action of vitamin D with cereal diets is due primarily to an improved utilization of inorganic P.