Apparent absorption and retention of Ca, Cu, Mg, Mn, and Zn from a diet containing bran

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Abstract
To establish conditions for comparisons of mineral bioavailability from plant sources, seven male subjects consumed a constant diet containing bran fiber and phytate. Absorption and retention of Ca, Cu, Mg, Mn, and Zn were measured for 7-day periods through wk 2–7. Intakes of Mg, Mn, and Zn significantly exceeded the RDA; Ca and Cu intakes were only slightly in excess of RDA. All mineral retentions fluctuated from week to week but only Mg and Mn showed a consistent positive trend over time. Phytate excretions showed characteristic individual patterns, but did not appear to change with time. In contrast to previous observations fecal recovery of polyethyleneglycol (PEG) (MW = 4000) was consistently lower than recovery of simultaneously ingested Cr. Only five of the seven subjects returned close to 100% of Cr within 7 days. It was concluded that at least 4 wk were needed for adaptation in investigations involving more than one mineral when the experimental diet is adequate in the nutrients under investigation, that measurements of responses to treatment required 2–3 wk each, and that successive isotopically labeled test meals may overlap if they are spaced at 7-day intervals.