Nutritional evaluation of mineral intake=Comparison of the food composition table method and food duplicate-ICP analysis method

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Daily dietary intakes of 28 trace elements were estimated from 24-food duplicate records of 456 adult women. The estimates made it possible to classify the elements into three groups of high (i.e., >1 mg/day as a median ; 7 elements of Al, Cu, Mg etc.), medium (2-985 ug/day ; 13 elements of As, B,Ba, Be etc.) and low intake (<1 ug/day ; 5 elements of Cd, Co, Li etc.). Published values for the element intake were available for 15 elements among the 28. Comparison showed that the food composition-based estimates tended to agree with the published values only when the estimated intakes were above 1 ug/day, but the discrepancies were evident for four elements of low intake (i.e., <1 ug/day). In a subsequent study, 24-hour total food duplicates were collected from 231 adult women in 9 prefectures in Japan, and dietary intakes of 5 minerals [sodium (Na), potassium (K), phosphorus (P), calcium (Ca) and iron (Fe) ] were estimated from the weights of food items in each duplicate sample by use of food composition tables. Food components in each duplicate sample was homogenized and wet-ashed for element determination by inductively-coupled plasma spectrometry (ICP). The comparison of the two sets of values, the estimates and ICP-measured values, showed that the estimates were significantly larger than the measured values in cases of Na (the ratio of the estimated over the measured ; 118%), K (115%), Ca (109%) and Fe (130%), whereas the two values did not differ from each other in case of P (the ratio ; 93%). Thus, food composition-based estimation carries the risk of over-estimation in case of Na, K,Ca and Fe, but not so in case of P.