Studies in Calcium Metabolism. Effect of Food Phytates on Calcium45 Uptake in Boys on a Moderate Calcium Breakfast

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Abstract
Seventeen boys were given two test breakfasts, one of oatmeal and one of farina, at an interval of three weeks, for the purpose of comparing calcium uptake in the presence and in the absence of food phytate. The boys had subnormal intelligence but were otherwise normal, were institutionalized under relatively uniform conditions. The two test breakfasts contained, respectively: 220 and 220 ml of milk; 241 and 237 mg of Ca., 80 and 0 mg phytic P; and 0.85 and 0.85 µc of Ca45. Ca uptake was studied by determining the Ca45 contents of the serum samples taken 2.5 hours following ingestion of the test breakfast, and by measuring the Ca45 output in pooled urine and stool specimens collected for 72 and 120 hours, respectively, following ingestion of the Ca45-labeled meals. The specific activities of the serum and urine samples obtained from these subjects were not significantly changed when the cereal of the test breakfast was changed from oatmeal to farina, or the reverse. For purposes of a criss-cross design the individuals had been divided into two subgroups. The fecal output of Ca45 of each subgroup was affected significantly by changing the cereal of the test breakfast from oatmeal to farina. However, the direction of change was opposite for each subgroup. When the results of the fecal output of the two subgroups were pooled, the difference between the two test breakfasts was no longer significant. The percentage of absorbed Ca decreased as the Ca intake increased. It is concluded that phytates do not exert a significant effect on Ca45 absorption when the meal provides 239 mg of Ca and when the phytic P intake is 80 mg. Because this ratio of Ca to phytic P is typical of diets in the United States, it may be concluded that food phytates are of no nutritional concern in this country.