An attempt to measure the availability of calcium in edible leaves commonly consumed by South African negroes

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Abstract
Most primitive and emerging populations obtain their calcium, largely or almost wholly, from vegetable sources. Of these, edible leaves (wild and cultivated), in certain contexts, are very important. To throw light on the availability of the calcium content, five common types of cooked edible leaves or “spinaches”, all having low concentrations of oxalic acid, were fed in amounts containing about 200 mg calcium, to groups of South African Negro children. Urinary calcium excretions, accruing over 6 hour periods, were determined. The mean amounts of calcium excreted were of the same order and similar to that resulting from consumption of a volume of milk containing 200 mg calcium. Using the methodology described, it was confirmed that the calcium in Swiss Chard “spinach”, (Spinacia oleracea) with its high oxalic acid content, is poorly absorbed. Nevertheless, it is inferred that the calcium contained in leaves of “spinaches” commonly consumed is available for utilization, a finding in agreement with observations on South African Negroes with respect to the satisfactory composition, dimensions, and other related indices of bone which reflect calcium status.