ABSTRACT
There is increasing recognition among carotenoid researchers that the 20 or so individual carotenoids that enter the blood stream tend to target specic systems within the body. Lycopene, e.g., tends to preferentially accumulate in the prostate gland of men and beta-carotene within the corpus luteum of women. Perhaps one of the more noteworthy examples of exclusivity, however, is the primate eye (including the retina, retinal pigment epithelium, ciliary tissue, crystalline lens, etc; Bernstein et al., 2001), which accumulates only lutein (L), zeaxanthin (Z), and the intermediary isomer, meso-Z (Bone et al., 1988; Bone et al., 1997). This accumulation is quite variable across individuals (e.g., Hammond et al., 1997). The primary driver appears to be the dietary intake of carotenoid-rich foods (even in infancy, see Figure 5.1), which can range from average levels that are quite low in the United States (about 1-2 mg/day of L and Z) to levels that, in some cultures, would be considered megadosing (mean intake of about 20 mg/day of L and Z in Fiji Islanders; Le Marchand et al., 1993). Once ingested, the probability that the carotenoids will actually reach their target tissue is moderated by numerous factors. These variables, roughly segregated, reect a balance of deleterious (largely pro-oxidant) and protective factors: deleterious variables tend to lower pigment levels (smoking, obesity, diabetic status, etc.), whereas more salubrious factors (such as a healthy diet) appear to allow more direct uptake (i.e., no systemic reduction) within the target tissue (reviewed by Hammond and Johnson, 2002). Whether high or low, however, the eye accumulates just these two isomers with distinct specicity: e.g., in adult retina, Z concentrates
Introduction ..............................................................................................................97 Effects of L and Z during Visual Development: Infancy and Childhood ............... 100 Effects of L and Z on the Visual Function of Healthy Adults ................................ 103 Effects of L and Z on the Aging and Diseased Visual System ............................... 104 Effect of Other Carotenoids on the Visual System ................................................ 105 Conclusion ............................................................................................................. 106 References .............................................................................................................. 107
in the very center whereas L is spread more evenly throughout the retinal tissue (Bone et al., 1997, 1988).
