Lutein intake decreases risk of late but not early AMD The findings of a meta-analysis indicate that dietary lutein and zeaxanthin is not significantly associated with a reduced risk of early AMD, whereas an increase in the intake of these carotenoids may be protective against late AMD.

Dietary antioxidants, particularly lutein and zeaxanthin, are hypothesized to have the capacity to modulate defense and repair systems that operate in response to oxidative damage and inflammation. As the major components of macular pigment, lutein and its structural isomer, zeaxanthin, are thought to have the beneficial effects on preventing the onset and progression of AMD. Laboratory data suggested an important role for these two carotenoids in protecting the neural retina from photo-oxidative damage and the development of common visually disabling disorders by absorbing blue light and by quenching reactive oxygen species through powerful antioxidant activity.

Lutein and zeaxanthin are thought to decrease the incidence of age-related macular degeneration (AMD); however, findings have been inconsistent.

Methods & Results

The researchers conducted a systematic literature review and meta-analysis to evaluate the relationship between dietary intake of lutein and zeaxanthin and AMD risk. Relevant studies were identified by searching five databases up to April 2010. Reference lists of articles were retrieved, and experts were contacted. Literature search, data extraction and study quality assessment were performed independently by two reviewers and results were pooled quantitatively using meta-analysis methods. The potential sources of heterogeneity and publication bias were also estimated.

The search yielded six longitudinal cohort studies. The pooled relative risk (RR) for early AMD, comparing the highest with the lowest category of lutein and zeaxanthin intake, was 0.96 (95 % CI 0.78, 1.17). Dietary intake of these carotenoids was significantly related with a reduction in risk of late AMD (RR 0.74; 95 % CI 0.57, 0.97); and a statistically significant inverse association was observed between lutein and zeaxanthin intake and neovascular AMD risk (RR 0.68; 95 % CI 0.51, 0.92). The results were essentially consistent among subgroups stratified by participant characteristics.

Discussion & Conclusions

The present meta-analysis involved data on evaluating the effects of lutein and zeaxanthin on AMD prevention published in six cohort studies. Results suggested that high intake of lutein and zeaxanthin was significantly associated with a reduction in risk of late AMD (FIGURE). No significant relationship was found for dietary intake of these carotenoids and early AMD (FIGURE).

Several biological mechanisms have been proposed for the potential protective effect of lutein and zeaxanthin on preventing the onset of AMD. As the major components of macular pigment, lutein and zeaxanthin are uniquely concentrated at the macula, indicating that these carotenoids may exert their effects on protecting the macula from age-related loss of visual function and macular disease. Both lutein and zeaxanthin, possessing a series of unconjugated double bonds, are believed to be very effective antioxidants. They have been shown to help quench singlet oxygen, scavenge reactive free radicals and inhibit lipid peroxidation of membrane phospholipids, and thus may prevent or delay the development of AMD. In addition, the spectrum of lutein and zeaxanthin includes a broad absorption band, with a peak at approximately 450 nm; therefore, these carotenoids have an important role in absorbing and attenuating the damaging blue light before it reaches the photoreceptors.

As there were no randomised clinical trials regarding the effect of dietary lutein and zeaxanthin on AMD prevention at present. It is generally considered that cohort studies provide stronger evidence for evaluating a relationship than other observational studies, because the cohort studies could largely reduce the likelihood of selection bias and reverse causation. Therefore, only cohort studies were included in the present systematic review and meta-analysis.

Results from the present analysis showed that lutein and zeaxanthin intake was not significantly associated with a decrease in the risk of developing early AMD. Among the six available studies, only one found a significant association between dietary lutein and zeaxanthin and the incidence of early AMD, whereas the others found no associations that were consistent with the present finding.

In contrast with the findings for early AMD, we found a statistically significant relationship between lutein and zeaxanthin intake and the risk of late AMD. These inconsistent relationships from different stages of AMD might be partly explained by differences in the degree of macular pigment damage and ascertainment of AMD. Previous studies had shown that no significant differences in macular pigment optical density were found between eyes with and without early AMD or between the various stages of early AMD. Results from studies that compared the macular pigment optical density of eyes with and without late AMD were not consistent; however, most indicated declines in the optical density of macular pigment among subjects with late AMD. Similar results had also been found in the peripheral retina of autopsy specimens from donor eyes with AMD, indicating that the loss of macular pigment might reflect the accumulation of damage accrued over an entire lifespan.

In conclusion, the present systematic review and metaanalysis demonstrates that, on the basis of evidence available to date, dietary intake of lutein and zeaxanthin is not significantly associated with a decrease in the risk of developing early AMD, whereas an increase in the intake of xanthophylls may have beneficial effects for late AMD.

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Br J Nutr. 2012 Feb;107(3):350-9