The amount of dietary trace elements absorbed from a meal depends, among other factors, on the quantities of certain minor plant constituents present in the meal. These substances can act as ligands and bind trace elements in the digestive tract in available or unavailable forms for absorption. The present study was designed to investigate the extent to which different polyphenols (PP) may influence Zn and Cu absorption in rats. Different PP of nutritional interest (chlorogenic acid, caffeic acid, catechin and rutin) were studied using meals extrinsically-labelled with stable isotopes67Zn and 65Cu. Male Wistar rats were fed on a non-labelled semi-synthetic diet containing (mg/kg) 38 Fe, 35 Zn and 7·5 Cu for 8 d. PP were dissolved in dimethyl sulfoxide as the solvent and added to the meal at 1 g/kg during 3 d before isotope administration and until the end of the experiment (a further 3 d). The control group received the dimethyl sulfoxide only. After overnight food deprivation, rats were fed on the labelled test meals (4 g diet+0·1 mg 67Zn and 0·1 mg 65Cu) with 0·5 mg Dy as a faecal marker. Faeces and urine pools were collected for 3 d and analysed for 67Zn and65 Cu isotopic enrichment using the inductively-coupled plasma mass spectrometry technique. Zn absorption was significantly less in rats fed on chlorogenic acid or caffeic acid than in the control group. Catechin ingestion non-significantly inhibited 67Zn absorption. However, the PP studied were without effect on Cu absorption. The study illustrates the effect of metal-binding phenolic compounds on mineral nutrition in the rat, and the possible importance of the effects of different foods rich in these compounds on mineral absorption in man.
Short-term ingestion of chlorogenic or caffeic acids decreases zinc but not copper absorption in rats, utilization of stable isotopes and inductively-coupled plasma mass spectrometry technique
