Use of a C tracer to quantify the plasma appearance of a physiological dose of lutein in humans

Increased intake of lutein from vegetables promotes increased density of the macular pigment and therefore may protect against age-related macular degeneration.

Our objective was to use a C-tracer and high-precision gas chromatography-combustion interfaced-isotope ratio mass spectrometry (GC-C-IRMS) to investigate metabolism of lutein dose equivalent to that absorbed from vegetables.

Biosynthetic per-labeled (>99% C) lutein was purified from a commercially available extract of of algal biomass. Subjects (n=4) ingested 3 mg of [C] lutein with a standardized low-carotenoid breakfast. Blood samples were collected at baseline and then hourly for 12 h ; additional blood samples were drawn at 16, 24, 48, 72, 96, 192, 360, and 528 h. To produce parhydro-beta-carotene suitable for analysis by GC-C-IRMS, the plasma lutein fraction was hydrogenated on palladium-on-carbon catalyst with acid-catalyzed hydrogenolysis. The stable carbon isotope (C/C) ratio mesasured by GC-C-IRMS was used to calculate the plasma concentration of [C] lutein. There was a rapid increase in [C] lutein in plasma until peak enrichment at 16 h followed by by a decline to the next measurement at 24 h. At 528 h, small changes in C enrichment from baseline could still be measured in plasma lutein. High-precision GC-C-IRMS enables complete definition of the appearance and disappearance of [C] lutein in plasma after ingestion of a dose similar to that absorbed from foods.