Suzen M. Moeller

The Potential Role of Dietary Xanthophylls in Cataract and Age-Related Macular Degeneration

The carotenoid xanthophylls, lutein and zeaxanthin, accumulate in the eye lens and macular region of the retina. Lutein and zeaxanthin concentrations in the macula are greater than those found in plasma and other tissues. A relationship between macular pigment optical density, a marker of lutein and zeaxanthin concentration in the macula, and lens optical density, an antecedent of cataractous changes, has been suggested. The xanthophylls may act to protect the eye from ultraviolet phototoxicity via quenching reactive oxygen species and/or other mechanisms. Some observational studies have shown that generous intakes of lutein and zeaxanthin, particularly from certain xanthophyll-rich foods like spinach, broccoli and eggs, are associated with a significant reduction in the risk for cataract (up to 20%) and for age-related macular degeneration (up to 40%). While the pathophysiology of cataract and age-related macular degeneration is complex and contains both environmental and genetic components, research studies suggest dietary factors including antioxidant vitamins and xanthophylls may contribute to a reduction in the risk of these degenerative eye diseases. Further research is necessary to confirm these observations.

Associations Between Age-Related Nuclear Cataract and Lutein and Zeaxanthin in the Diet and Serum in the Carotenoids in the Age-Related Eye Disease Study (CAREDS), an Ancillary Study of the Women's Health Initiative

OBJECTIVE To evaluate associations between nuclear cataract (determined from slitlamp photographs between May 2001 and January 2004) and lutein and zeaxanthin in the diet and serum in patients between 1994 and 1998 and macula between 2001 and 2004. DESIGN A total of 1802 women aged 50 to 79 years in Iowa, Wisconsin, and Oregon with intakes of lutein and zeaxanthin above the 78th (high) and below the 28th (low) percentiles in the Womens Health Initiative Observational Study (1994-1998) were recruited 4 to 7 years later (2001-2004) into the Carotenoids in Age-Related Eye Disease Study. RESULTS Women in the group with high dietary levels of lutein and zeaxanthin had a 23% lower prevalence of nuclear cataract (age-adjusted odds ratio, 0.77; 95% confidence interval, 0.62-0.96) compared with those with low levels. Multivariable adjustment slightly attenuated the association (odds ratio, 0.81; 95% confidence interval, 0.65-1.01). Women in the highest quintile category of diet or serum levels of lutein and zeaxanthin as compared with those in the lowest quintile category were 32% less likely to have nuclear cataract (multivariable-adjusted odds ratio, 0.68; 95% confidence interval, 0.48-0.97; P for trend = .04; and multivariable-adjusted odds ratio, 0.68; 95% confidence interval, 0.47-0.98; P for trend = .01, respectively). Cross-sectional associations with macular pigment density were inverse but not statistically significant. CONCLUSIONS Diets rich in lutein and zeaxanthin are moderately associated with decreased prevalence of nuclear cataract in older women. However, other protective aspects of such diets may in part explain these relationships.

Association Between Dietary Fat Intake and Age-Related Macular Degeneration in the Carotenoids in Age-Related Eye Disease Study (CAREDS) An Ancillary Study of the Women's Health Initiative

OBJECTIVE To evaluate the relationships between the amount and type of dietary fat and intermediate age-related macular degeneration (AMD). DESIGN Women aged 50 to 79 years with high and low lutein intake from 3 sites of the Womens Health Initiative Observational Study were recruited into the Carotenoids in Age-Related Eye Disease Study. Fat intake from 1994 through 1998 was estimated using food frequency questionnaires, and AMD was assessed photographically from 2001 through 2004. RESULTS Intakes of omega-6 and omega-3 polyunsaturated fatty acids, which were highly correlated (r = 0.8), were associated with approximately 2-fold higher prevalence of intermediate AMD in high vs low quintiles. However, monounsaturated fatty acid intake was associated with lower prevalence. Age interactions were often observed. In women younger than 75 years (n = 1325), total fat and saturated fatty acid intakes were associated with increased prevalence of AMD (multivariate adjusted odds ratios [95% confidence interval] for intermediate AMD, 1.7 [1.0-2.7] for quintile 5 vs quintile 1 for total fat [P = .10 for trend] and 1.6 [0.7-3.6] for saturated fatty acids [P = .23 for trend]). The associations were reversed in older women. CONCLUSIONS These results support a growing body of evidence suggesting that diets high in several types of fat may contribute to the risk of intermediate AMD and that diets high in monounsaturated fatty acids may be protective.

Healthy diets and the subsequent prevalence of nuclear cataract in women.

OBJECTIVE To assess the association between healthy diet scores and prevalence of nuclear cataract in women. METHODS The association between healthy diet scores, which reflect adherence to the US dietary guidelines, and prevalence of nuclear cataract determined 4 to 7 years later was assessed in a sample of Womens Health Initiative Observational Study participants (aged 50-79 years) residing in Iowa, Wisconsin, and Oregon. Scores on the 1995 Healthy Eating Index, which reflect adherence to 1990 guidelines, were assigned from responses to food frequency questionnaires at the Womens Health Initiative baseline (1994-1998). Presence of nuclear cataract was determined from slitlamp photographs and self-reports of cataract extractions were assessed from May 1, 2001, to January 31, 2004, in 1808 women participating in the Carotenoids in Age-Related Eye Disease Study. RESULTS Having a high 1995 Healthy Eating Index score was the strongest modifiable predictor of low prevalence of nuclear cataract among numerous risk factors investigated in this sample. The multivariate-adjusted odds ratio for high vs low quintile for diet score was 0.63 (95% confidence interval, 0.43-0.91). Higher prevalence of nuclear cataract was also associated with other modifiable factors (smoking and marked obesity) and nonmodifiable factors (having brown eyes, myopia, and high pulse pressure). Vitamin supplement use was not related to cataract. CONCLUSION These data add to the body of evidence suggesting that eating foods rich in a variety of vitamins and minerals may contribute to postponing the occurrence of the most common type of cataract in the United States.

The effects of high fructose syrup.

High fructose corn syrup (HFCS) has become an increasingly common food ingredient in the last 40 years. However, there is concern that HFCS consumption increases the risk for obesity and other adverse health outcomes compared to other caloric sweeteners. The most commonly used types of HFCS (HFCS-42 and HFCS-55) are similar in composition to sucrose (table sugar), consisting of roughly equal amounts of fructose and glucose. The primary difference is that these monosaccharides exist free in solution in HFCS, but in disaccharide form in sucrose. The disaccharide sucrose is easily cleaved in the small intestine, so free fructose and glucose are absorbed from both sucrose and HFCS. The advantage to food manufacturers is that the free monosaccharides in HFCS provide better flavor enhancement, stability, freshness, texture, color, pourability, and consistency in foods in comparison to sucrose. Because the composition of HFCS and sucrose is so similar, particularly on absorption by the body, it appears unlikely that HFCS contributes more to obesity or other conditions than sucrose does. Nevertheless, few studies have evaluated the potentially differential effect of various sweeteners, particularly as they relate to health conditions such as obesity, which develop over relatively long periods of time. Improved nutrient databases are needed to analyze food consumption in epidemiologic studies, as are more strongly designed experimental studies, including those on the mechanism of action and relationship between fructose dose and response. At the present time, there is insufficient evidence to ban or otherwise restrict use of HFCS or other fructose-containing sweeteners in the food supply or to require the use of warning labels on products containing HFCS. Nevertheless, dietary advice to limit consumption of all added caloric sweeteners, including HFCS, is warranted.

Women's Health Initiative Diet Intervention Did Not Increase Macular Pigment Optical Density in an Ancillary Study of a Subsample of the Women's Health Initiative

In this study, we examined the impact of long-term (>8 y), low-fat, high-fruit and -vegetable diets on levels of lutein and zeaxanthin in the macula of the retina, as indicated by the OD of macular pigment. Macular pigment OD, measured by heterochromatic flicker photometry, was compared in women aged 60-87 y, who, 7-18 mo earlier (median 12 mo), had been in the dietary modification intervention (n = 158) or comparison (n = 236) groups of the Womens Health Initiative (WHI) at the Madison, WI site for a mean of 8.5 y. Women in the intervention group ate more fruits and vegetables (mean +/- SEM) (6.1 +/- 0.2 vs. 4.6 +/- 0.2 servings/d; P < 0.0001) and had higher intakes of lutein and zeaxanthin from foods and supplements (2.7 +/- 0.2 vs. 2.1 +/- 0.1 mg/d; P = 0.0003) than the comparison group. However, macular pigment density did not differ between the intervention (0.36 +/- 0.02 OD units) and comparison (0.35 +/- 0.01 OD units) groups. It tended to be higher (11%; P = 0.11) in women consuming lutein and zeaxanthin in the highest compared with the lowest quintile (median 6.4 vs. 1.1 mg/d). The increase in fruit and vegetable intake among dietary modification participants of this WHI subsample was not of sufficient magnitude to alter the mean density of retinal carotenoids, given other existing dietary conditions in this sample.

Ethnic differences in diet and age-related maculopathies.

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in people past the age of 65 in the United States and other developed countries, affecting 1.7 million elders. Even more people have been found to have early lesions, which, although not affecting vision, are believed to increase risk for AMD. Epidemiological studies have found that AMD rates vary between different population subgroups, both within the United States and around the world. These population subgroups are usually defined by their racial or national affiliation, or ancestry, which is broadly referred to as a group’s ethnicity. This variation in occurrence of AMD could reflect the prevalence of different genetic, lifestyle, or environmental factors among people of different ethnicities. Some of the first clues for risk factors for a disease come from studies that compare rates of disease across different nations or geographical regions of the world. This is not possible with AMD, as rates are not routinely monitored, and the definition of and methods to assess AMD vary widely. We can perhaps learn about such population differences by studying rates of AMD in ethnic groups within one region. In this chapter, we describe differences in prevalence of AMD across ethnic groups and the degree to which these may reflect differences in diet. We also briefly touch on the possibility that diet may impact AMD differently in people of different ethnic backgrounds.