The serum concentrations of xanthophylls at the end of the 7×/wk supplementation schedule and at the time of death are presented for comparison, with postmortem tissue concentrations shown in
Table 3 . Longitudinal measures of serum xanthophylls in these monkeys over the course of L and Z supplementation have been reported.
15 The unsupplemented xanthophyll-free monkeys had no detectable xanthophylls in serum and are not included in the table. There was a trend toward higher total xanthophyll concentrations in the L-fed group (
P = 0.052) at the end of the 7×/wk supplementation period but no difference at study’s end (
P = 0.2). In the L-fed monkeys, serum concentrations of L were significantly lower at the study’s end than at the end of the 7×/wk supplementation period (
P < 0.015), but in the Z-fed group there was no difference between the two time points. Serum xanthophyll concentrations at the end of the study were significantly higher in both the L- and Z-fed groups than in the stock-diet control group (
P < 0.014 and
P < 0.0001, respectively). Serum L in the L-fed monkeys was entirely in the
trans form. Serum Z in the Z-fed monkeys was in both the
trans (72%) and
cis (27%) forms. There was also a small amount of 3′ dehydrolutein (1%) present in the serum of these animals. The identification of this metabolite as 3′ dehydrolutein was suggested by coelution with a known standard, absorption spectra comparison with a known standard, and LC/MS (data not shown). Final serum xanthophyll concentration was not significantly related to sex or n-3 fatty acid status (by two-way ANOVA) or to body weight or the duration of supplementation (by linear regression), and the difference between the Z- and L-fed groups remained nonsignificant when adjusted for these factors by ANCOVA. Although serum xanthophyll concentrations initially decreased after the reduction in the frequency of supplementation,
15 the duration of 4×/wk supplementation was not related to final serum xanthophyll levels (
P = 0.366, overall;
P = 0.857 for the L-fed group and 0.790 for the Z-fed group).