title: The carotenoid conundrum: improved nutrition boosts plasma carotenoid levels but not immune benefits of carotenoid supplementation.
abstract: Carotenoids are widely heralded as central to honest signaling due to their dual roles as pigments and antioxidants/immunostimulants. The aim of this study is to test if diet quality and carotenoids alone or in an interaction influence condition, carotenoid availability in plasma and immune responsiveness. Therefore, a diet experiment during the moult of great tits, Parus major, was performed. In a two-way design, we manipulated general quality (digestibility, protein and vitamin content) as well as carotenoid (lutein) content of semi-synthetic diets. Higher quality diet improved individual condition since birds had greater body mass, and to a lesser extent, higher hematocrit. In addition to the expected positive effect of carotenoid supplementation and individual lutein consumption on circulating lutein, there was a positive effect of enhanced diet quality on plasma carotenoid levels. Carotenoid supplementation, but not diet quality, improved the local inflammatory response and maintenance of body mass during a humoral immune reaction. The enhancement of circulating carotenoid levels by improved general quality of the diet or individual condition could provide a testable, mechanistic explanation for the variation in effects of carotenoid supplementation studies.
authors.affiliation: Behavioural Ecology of Sexual Signals Group, Max Planck Institute for Ornithology, Radolfzell, Germany. Anne.Peters@monash.edu
authors.forename: Anne
authors.initials: A
authors.lastname: Peters
authors.forename: Steffen
authors.initials: S
authors.lastname: Magdeburg
authors.forename: Kaspar
authors.initials: K
authors.lastname: Delhey
mesh_terms: D000818:Animals; D002338:Carotenoids / Q000097:blood*; D004032:Diet; D019587:Dietary Supplements; D004435:Eating; D056724:Immunity, Humoral; D007249:Inflammation / Q000139:chemically induced; D014975:Lutein / Q000008:administration & dosage*; D008297:Male; D009752:Nutritional Status; D010835:Phytohemagglutinins; D020308:Songbirds / Q000097:blood* / Q000276:immunology
chemical_list: D010835:Phytohemagglutinins; D002338:Carotenoids; D014975:Lutein