In vitro determination of zinc dialyzability from duplicate hospital meals: influence of other nutrients

ObjectivesWe determined zinc (Zn) dialyzability as an indicator of Zn bioavailability in the in vitro gastrointestinal digests of 108 duplicate meals. The interaction exerted by levels of 51 nutrients and energy on total and dialyzable Zn fractions and on Zn dialyzability was also assessed.MethodsTotal and dialyzable Zn levels were measured by flame atomic absorption spectrometry. The Zn dialyzability is expressed as the percentage of dialyzed Zn in relation to the total Zn content in duplicate meals (dialysis Zn percentages).ResultsThe mean total and dialyzable Zn fractions and Zn dialyzability were 2.180 ± 1.806 mg, 0.478 ± 0.556 mg, and 25.23 ± 15.05%, respectively. The dialysis Zn levels increased significantly with total Zn content in duplicate meals (P < 0.001, r = 0.690). Total and dialyzable Zn fractions found in breakfasts were significantly lower (P < 0.001). The Zn dialyzability was significantly correlated only with total chromium contents, dialyzable copper (Cu) and manganese (Mn) fractions, and Cu and Mn dialyzabilities (P < 0.05). Zn dialyzabilities decreased significantly with increased daily Zn intakes (P = 0.010, r = 0.423). The total Zn supply by meals was directly and significantly (P < 0.001) correlated with their macronutrient contents (carbohydrates, protein, and fiber). The mean daily Zn intake determined was 6.541 mg.ConclusionDuplicate diets studied are moderately low Zn-bioavailability diets. The protein and derivate amino acids act as formers of soluble complexes with Zn in the gastrointestinal tract. Daily Zn levels supplied by hospital meals are low.