|Grusak, Michael - Mike|
Submitted to: Journal of Nutritional Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2003
Publication Date: 11/1/2003
Citation: Lienaua,L., Glaserb,T., Tang,G., Dolnikowskib,G.G., Grusak,M.A., Alberta,K. 2003. Bioavailability of lutein in humans from intrinsically labeled vegetables determined by LC-APCI-MS. Journal of Nutritional Biochemistry. 14(11):663-670. Interpretive Summary: Lutein is a pigment molecule found in plants and plant food products, which has been shown to provide beneficial health effects in humans. Lutein has antioxidant properties, and also is an important carotenoid found in the retina of eyes. Although it is known that various foods contain lutein, little is known about how lutein is absorbed in the human gut when it is consumed in a complex meal. In order to provide guidance to consumers as to the percentage of lutein that might be absorbed from various foods (that is, its bioavailability), we developed a tracer method for determining the relative bioavailability of food-derived lutein in humans. Spinach and collard plants were grown with a special form of water (non-radioactive heavy water) which allowed us to label lutein molecules in the leafy vegetables. These vegetables were fed in a complete meal to study subjects; blood samples were then collected over a one month period. We were able to identify, or trace, the labeled lutein in the blood of the human subjects using mass spectrometry instrumentation, and thereby measured the relative absorption of lutein from each food. This technique should enable us to study lutein bioavailability from different foods of diverse carotenoid composition, and following different cooking procedures.
Technical Abstract: The aim of the investigation was to assess a stable isotope method for determining the relative bioavailability of food-derived lutein in humans. Subjects were administered a single dose of deuterium-labeled carotenoids from intrinsically labeled spinach or collard green; 10 mL blood samples were drawn at various time points over a 34 d period. The vegetables had been hydroponically grown using 25 atom-% deuterated water. Lutein molecules in the vegetables were partially deuterated with a highest abundance isotopomer at M0 + 8 (unlabeled molecular mass, M0, plus 8 additional mass units from 8 deuterium atoms in the molecules). This allowed labeled lutein to be distinguished from endogenous lutein in serum samples after consuming the labeled meal. The presence of labeled lutein in the circulation was determined by liquid chromatography-mass spectrometry (LC/MS) equipped with an atmospheric pressure chemical ionisation (APCI-MS) interface. The quantification of the labeled lutein in serum samples enabled the calculation of the enrichment for each time point after the dose; these values were plotted versus time to generate absorption-clearance curves for each of the subjects. Area under the curve analyses of four different subjects (integrated over 29 d) yielded relative bioavailabilities of 226 to 461 nmole-day/mg lutein, following acute feeding doses of 9.8 to 18.8 mg labeled lutein. This technique will facilitate the study of lutein bioavailability from different foods of diverse carotenoid composition and/or following various food preparation procedures.