In the previous EduFacts ("Dietary Carotenoids, Smoking, & Age-Related Macular Degeneration") data from the Eye Disease Case Control Study (1) were presented, which suggested that high intake of the carotenoids lutein and zeaxanthin may modulate some of the risk of age-related macular degeneration AMD associated with smoking. While smoking has been identified as a risk factor for AMD since the early 1980's, the etiology of this risk factor has remained unclear even among recent studies. Generally the clinical studies suggest that smoking causes atherosclerotic and hypoxic damage to the choroidal vasculature resulting in maculopathy, or that smoking directly causes oxidative damage to retinal cells. In a 1996 report by Hammond and colleagues (2), 34 smokers were compared with 34 non-smokers matched for the following variables: age, weight, sex, degree of pigmentation (of eyes, skin and hair), dietary intake of carotenoids, fat, and iron. Macular pigment (retinal carotenoid) density was measured with a psychophysical method described in the paper. The main result of the study was that non-smokers had over twice the macular pigment density as smokers (p<0.0001). Almost 2/3 of the smokers had extremely low macular pigment densities. Since the investigators matched smokers and non-smokers on dietary carotenoid intake, smoking seems to be associated independently with substantially reduced retinal carotenoid density.

However the few smokers in the study who did have higher macular pigment densities, also had very high (> 2 std deviations above the mean) dietary carotenoid intake. This supports the suggestion by Seddon and colleagues that increasing the macular pigment density through increased intake of lutein/zeaxanthin could ameliorate some of the risk of AMD associated with smoking (1).

References

1. Seddon JM, Ajani UA, Sperduto RD et al. Dietary Carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. JAMA 1994; 272: 1413-1420.
2. Hammond BR, Wooten BR, Snodderly DM. Cigarette smoking and Retinal Carotenoids: Implications for Age-Related Macular Degeneration. Vision Res 1996; 36(18): 3003-3009.