The Effect of “High Fibre Biscuits” on Urinary Risk Factors for Stone Formation

Abstract

Idiopathic hypercalciuria is a common finding in stone formers¹⁻³. Conversely, a reduction in urinary calcium decreases the recurrence rate of stone formation⁴. Excessive absorption of calcium from the intestine is the major cause of hypercalciuria⁵, but an increased consumption of fibre may reduce urinary calcium^3,6 by binding calcium in the gut. If this is the mechanism by which fibre reduces urinary calcium, however, there is the risk that more oxalate might become available for passive absorption. This may produce marginal hyperoxaluria, as in the case of other calcium-binding agents, such as cellulose phosphate⁷. The most common form of fibre supplement is cereal bran which contains a variable quantity of oxalate. It is not known if this oxalate is “available” for absorption.