Analysis of total and dialyzable copper levels in duplicate meals by ETAAS: daily intake

The determination of total and dialyzable copper levels of 108 hospital meals by the duplicate diet sampling method was performed. The analysis of Cu levels was done by an electro thermal atomic absorption spectrometry (ETAAS) method developed. The criteria for the validation of the method [sample recoveries, repeatability, limit of detection, sensibility and analyses of the standard reference materials (BCR CRM 063R and CRM 185R)] demonstrated its reliability and accuracy. The total Cu supply by meals is directly and significantly (P < 0.001) correlated with their macronutrient contents. The mean total and dialyzable Cu levels were 314.0 ± 123.2 μg and 84.19 ± 50.96 μg, respectively. The mean dialysis Cu percentage was 25.95 ± 15.70%. The total and dialyzable Cu levels and dialysis Cu percentages (Cu bioaccesability) found in breakfasts were significantly lower (P < 0.001). The dialysis Cu levels enhance significantly with the total element contents. The dialysis Cu levels and dialysis Cu percentages present in meals were primary and significantly correlated with carbohydrates, fibre, P, Fe, cholesterol, protein and several amino acids (P < 0.01). Food like cereals, legumes and dry fruits are primary sources of bioaccesible Cu in the diet. The protein and derivate amino acids, previous digestion, form soluble complexes with Cu in the gastrointestinal tract enhancing significantly the element bioavailability. Dialyzable Cu levels and dialysis Cu percentages enhanced significantly with corresponding Cr levels of meals (P = 0.001). The mean Cu daily dietary intake (DDI) found was 941.5 μg/day. The method of duplicate diet sampling and analysis of Cu facilitates the most accurate and reliable results and considers the influence of technological and cooking processes. The Cu DDIs reported indicate that probably no problems in relation to Cu nutrition could be observed in usual consumers of these meals (users and staff of the hospital).