Agreement of estimated values with measured values in dietary intakes of minerals: A validation study in Japan

This study was initiated to examine the validity of newly published food composition tables (FCT) as a tool for estimation of mineral intakes in Japan. For this purpose, 24-hour food duplicate samples were collected from residents in two areas. In practice, 24 adult women in one area and 17 adults (men and women) in the other offered complete samples (i.e. the samples with which the energy intakes were ≧1.2 times basal metabolic rates). The concentrations of nine minerals (Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn) in the duplicates were estimated by use of FCT, and compared with the values measured by flame atomic absorption spectrometry or inductively-coupled plasma atomic emission spectrometry. Close agreement was observed between the estimated values (E) and the measured values (M) on a group basis; the E/M ratios were in a range of 0.92-1.26. Lower limits of the 95% confidence interval of the ratio were, however, low, i.e. 0.42 for Ca, 0.54 for Na and 0.59 for Fe. The risk of over-estimation was highest for Mg (by +26%), Fe (by +22%) and Mn (by +22%). Thus, it appeared prudent to conclude that FCT-based estimation is reliable on a group basis for the minerals studied, and that care should be practiced, however, when application is made on an individual basis, especially for Ca, Fe and Na.