Lutein ester in serum after lutein supplementation in human subjects

Lutein, one of the major carotenoids present in serum, is also widely consu med by most populations. For the purpose of testing the potential health be nefits of several carotenoids, lutein was supplied as part of an interventi on trial to test whether the consumption of these food constituents reduces oxidative damage to human tissue components. Lutein from a natural source (15 mg/d as mixed ester forms) was supplied for 4 months to eighteen non-sm oking, apparently healthy volunteers (nine men, nine women) aged 25-45 year s. The serum carotenoid profile was analysed at baseline and monthly therea fter. On average, lutein concentrations increased 5-fold after the first mo nth of supplementation (mean 1.34 (range 0.6-3.34)mu mol/l). On reviewing t he results, in those volunteers whose lutein levels surpassed 1.05 mu mol/l (fourteen of seventeen), we tentatively identified lutein monopalmitate al ong with another unidentified ester (possibly from a monoketocarotenoid) in serum. Lutein levels returned to baseline values and eater forms were not present 3 months after supplementation was discontinued. Their concentratio ns did not correlate with, and represented less than 3% of, lutein levels a chieved in serum. They were observed before development of, and despite the presence of, carotenodermia. To our knowledge, this is the first time xant hophyll esters have been described in human serum. In view of the fact that xanthophyll esters have not been previously reported in serum and chylomic rons, it seems unlikely that these ester forms would be a reflection of the contents of the capsule. They may indicate a 'ceiling effect' on or satura tion of the transport capacity for xanthophylls, and may have been re-ester ified in vivo because of the unusual dietary conditions. The determination of the physiological importance of this finding will require further invest igation, although neither haematological nor biochemical changes were detec ted.