Intermittent and continuous faecal markers in short-term metabolic balance studies in young women.

I The continuous faecal marker chromic oxide, Cr,O,, and the intermittent marker brilliant blue were used together in metabolic balance studies of calcium and magnesium in two young women. 2. Faecal output was derived by four methods: no marker, brilliant blue, Cr,Os, or both brilliant blue and Cr,Os. 3. Balances of Ca and Mg derived by the four methods of obtaining faecal output were compared. 4. Recovery of ingested CrzOs in the faeces appeared complete in experiments on three further subjects, with only a negligible amount being excreted in the urine. 5. Simultaneous use of both types of marker is recommended for short-term balance studies of nutrients such as Ca and Mg which are not readily absorbed.