Copper absorption from foods labelled intrinsically and extrinsically with Cu-65 stable isotope

Abstract

Objective: To determine copper absorption from copper containing foods labelled either intrinsically or extrinsically with a highly enriched Cu-65 stable isotope label. Design: A longitudinal cross-over study. Setting: The study was conducted at the Institute of Food Research, Human Nutrition Unit, Norwich, UK. Subjects: Subjects were recruited locally via advertisements placed around the Norwich Research Park. A total of 10 volunteers (nine female, one male) took part in the study, but not all volunteers completed each of the test meals. Interventions: A highly enriched Cu-65 stable isotope label was administered to volunteers in the form of a reference dose or in breakfast test meals consisting of red wine, soya beans, mushrooms or sunflower seeds. Faecal monitoring and mass spectrometry techniques were used to estimate the relative quantities of copper absorbed from the different test meals. Results: True copper absorption from the reference dose (54%) was similar to extrinsically labelled red wine (49%) and intrinsically labelled sunflower seeds (52%), but significantly higher than extrinsically labelled mushrooms (35%), intrinsically (29%) and extrinsically (15%) labelled soya beans and extrinsically labelled sunflower seed (32%) test meals. Conclusions: The use of Cu-65 extrinsic labels in copper absorption studies requires validation according to the food being examined; intrinsic and extrinsic labelling produced significantly different results for sunflower seeds. Sponsorship: Funding from the European Commission and the Biotechnology and Biological Sciences Research Council.

Novel and Nontraditional Use of Stable Isotope Tracers To Study Metal Bioavailability from Natural Particles

“…Tracers are invaluable tools to investigate the fate of minerals and trace elements in various biological systems such as cell cultures, animals, and humans. − In environmental toxicology, nutrition, and biomedicine, tracers are commonly used to characterize the absorption, excretion, transport, and transformation of trace metals, − major cations, and nutrients. ,− The most common types of tracers are radioisotopes and enriched stable isotopes . Both share similar advantages such as low detection limits and the possibility to discriminate tracer from background and to work with multiple isotopes for some elements.…”

Use of stable isotopes to evaluate the functional effects of nutrients

“…Two stable isotopes, in addition to the most naturally abundant isotope, are necessary (therefore absorption of copper that has only two stable isotopes cannot be measured by the dual isotope method). A point to consider also is whether the orally ingested stable isotope is given in isolation or with food, and if the food is labelled intrinsically (biosynthetic incorporation) or extrinsically (mixed with the tracer) because different results can be obtained [56]. These methods have been used to investigate the effects of fructo-oligosaccharides on calcium [57,60] and trace element [54] absorption, or of phytate on zinc absorption [58].…”