The metabolic balance technique: a critical reappraisal.
Twenty-six metabolic balance studies (MBS) of Ca, Mg, and P have been conducted in 11 postmenopausal women with osteoporosis and in 4 patients suffering from Paget's disease of bone. Subjects were given a liquid formula diet (LFD) matched as closely as possible to the patient's home diet. Studies lasted for 25 days, separated into 5-day periods by a carmine marker combines with Cr2O3 as continuous fecal marker. The balance studies were combined with a tracer technique using 47Ca to detect a possible loss of Ca by perspiration. The reliability of analytical methods necessary for mineral balances was tested. In 22 of the 26 MBS a steady state (SS) reflecting the patient's regular living conditions was demonstrated, while a non-SS situation possibly due to changes of physical activity was seen in four instances. The overall precision and accuracy of this balance method for Ca and P was found to be better than plus or minus 50 mg/day after four periods and plus or minus 40 mg/day after five periods, as related to an average daily intake of 920 mg Ca and 1230 mg P. For Mg (intake 190 mg/day), a precision of plus or minus 10 mg/day was recorded. The dermal loss of Ca was found to be less than 20 mg/day. As shown for Ca, Mg and P, the precision of a balance study is only little enhanced when the investigation is continued for more than four periods. At the present time is not possible to predict non-SS situations before starting such a study but a simple formula is proposed to detect those which were not performed under SS conditions.
D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002136:Calcium, Dietary / Q000008:administration & dosage; D004032:Diet; D005243:Feces / Q000032:analysis; D005260:Female; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008433:Mathematics; D008593:Menopause; D008875:Middle Aged; D010001:Osteitis Deformans / Q000378:metabolism*; D010024:Osteoporosis / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D012867:Skin / Q000378:metabolism; D013997:Time Factors
D002132:Calcium Radioisotopes; D002136:Calcium, Dietary; D010758:Phosphorus; D008274:Magnesium; D002118:Calcium