Lehmann & Pollak [1942a] observed that the phosphates and carbonates of Ca and Mg were much more soluble in solutions of oa-amino-acids than they were in pure water, and it has since been shown that the solubility of commercial 'phytin ' can be increased in the same way. In consequence of their observations, Lehmann & Pollak suggested that amino-acids might facilitate the absorption of Ca. To prove or disprove this hypothesis, it was decided to study in human subjects the effect of varying protein consumption upon absorption and excretion of Ca and Mg. Subjects and experimental arrangements There have been five subjects, four men and one woman, and each has carried out two experiments, one at a high level and one at a low level of protein intake. A low protein and a moderately low Ca diet containing fixed rations of milk, 92 % wheatmeal bread, sugar and table fat, was given in both experiments. The rest of the basal diet was made up essentially of potatoes and other vegetables, flavoured and cooked in various ways. The fare varied from day to day during the first experiment, but the menus were repeated exactly during the second. Each person weighed out and ate as much of the vegetable dishes as he or she wished during the first experiment, and adhered to the same amounts during the second. These basal diets, which contained 45-70 g. of protein per day, were supplemented with 100-130 g. of protein (see Table 1) or with an equicalorific ration of sugar or fat. Four different sources of amino-acids were used to widen the scope of the investigation. All the protein supplements contained minerals, and, as far as possible, the intakes of Ca, Mg and P were made equal in the two experiments by administering a salt mixture with the sugar or fat supplement, or, alternatively, by reducing the milk ration when the protein intake was high. One of the protein supplements did not arrive in time to be analysed before the low protein experiment was well under way, and unfortunately in this case the Ca intakes were not equalized. The initials of the subjects, their ages, sex and weights, the duration of their experiments, the nature of their supplements and the * Beit Memorial Fellow.
