A supplementation study in human subjects with a combination of meso-zeaxanthin, (3R,3 0 R)-zeaxanthin and (3R,3 0 R,6 0 R)-lutein We measured the blood uptake of meso-zeaxanthin (MZ) from a mixture of macular pigments since its bioavailability in man has not been studied. Volunteers (ten men and nine women) were recruited and received one capsule of Lutein Plus w /d. Blood was taken at baseline, day 10 and day 22. One capsule contained 10·8 mg lutein, 1·2 mg (3R,3 0 R)-zeaxanthin and 8·0 mg MZ. Plasma lutein and total zeaxanthin concentrations were quantified using isocratic liquid chromatography and the eluting xanthophyll fractions were collected and re-chromatographed on a chiral column to assess the proportion of MZ. Plasma concentrations per mg dose at day 22 suggested that (3R,3 0 R)-zeaxanthin (0·088 mmol/l per mg) was about 50 % more actively retained by the body than lutein (0·056 mmol/l per mg) (although the difference was not significant in women) and 2·5-3·0 times more than MZ (0·026 mmol/l per mg). Concentrations of MZ at day 22 were 2·5 times higher in women than men. The plasma responses from lutein and (3R,3 0 R)-zeaxanthin in the Lutein Plus w were lower than literature values for the pure substances. That is, their uptake into plasma appeared to be slightly depressed by the presence of MZ. Plasma concentrations of b-carotene were depressed by about 50 % at day 10 and about 35 % at day 22. In conclusion, the lower plasma response to MZ compared with (3R,3 0 R)-zeaxanthin probably indicates that MZ is less well absorbed than (3R,3 0 R)-zeaxanthin but work with pure MZ will be needed to confirm that the lower plasma response was not due to the large amount of lutein in the Lutein Plus w .