Progress 10/01/03 to 09/30/06
Outputs
Loss of central vision in older adults is caused by a degenerative process in the macula of the human eye retina. The exact pathogenesis of this condition is unknown, but it appears from recent research that the macular pigment may play a role in protecting vision. The macular pigment is made up exclusively of the carotenoids lutein and zeaxanthin. These two plant pigments, known as xanthophylls, are found in a variety of foods, mostly green, yellow, and orange fruits and vegetables. Egg yolks are also a source of highly bioavailable xanthophylls. Clinical studies have consistently shown that an increase in dietary intake of xanthophylls leads to an increased macular pigment density. Results from epidemiological studies, however, have been inconsistent in demonstrating the association between dietary intake of plant xanthophylls, serum concentrations, and macular pigment density. No population studies to date have included eggs as a dietary source of lutein and
zeaxanthin. The objective of the study was to determine whether or not there is an association between egg consumption, lutein intake and central vision loss among community-dwelling older adults at risk for age-related macular degeneration (AMD). Egg intake was assessed with a survey questionnaire validated for content by older adults native to Kansas. Subjects were recruited from voter registration lists, newspaper advertisements, and local contacts. A total of 612 women and men provided responses for known and potential risk factors for macular degeneration in addition to the food items. Macular degeneration was ascertained by self-report in response to the question: "Has your eye doctor ever told you that you have age-related macular degeneration?" Individuals, rather than eyes, were the category of analysis for the outcome variable. Subjects who reported a diagnosis of macular degeneration (n=105) compared to subjects who reported no changes in the macula (n=507) were older (75+
years), had a known family history of macular disease, had a history of high cholesterol, and were farsighted. After adjusting for these four independent risk factors, none of the egg intake variables showed a significant inverse trend with higher consumption. There was a modest reduced risk of macular degeneration (OR:0.80; 95% CI:0.41,1.54) in the upper 25% level of total egg intake. These exploratory data suggest that reversing the trend of decreased consumption of eggs and egg products may provide a protective effect on age-related macular degeneration. The biologic plausibility exists for the role of egg yolks in increasing macular pigment density, which may provide protection from damage to the photoreceptors critical to central vision. The finding from our analysis of no relationship between dietary egg intake and central vision loss may be mediated by the relatively limited egg intake in our study participants.
Impacts
The purpose of this project is to assess the consumption of eggs and egg products and to estimate the total lutein intake. The results of this study will be a first step in gathering evidence of eggs as a nutritionally dense, high quality, inexpensive source of carotenoids needed to produce the macular pigment. Increasing the density of the pigment may aid in protecting the macula from damage and thereby reduce the risk of central vision loss in older adults.
Publications
- Holcomb CA. Consumption of carotenoid-rich foods and central vision loss. Journal of Nutrition for the Elderly 2004;24(1):1-18
- Allen C. Egg consumption and age-related macular degeneration: A pilot study. PhD Dissertation, Kansas State University, 2004.
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Progress 01/01/05 to 12/31/05
Outputs
Loss of central vision in older adults is caused by a degenerative process in the macula of the human eye retina. The exact pathogenesis of this condition is unknown, but it appears from recent research that the macular pigment may play a role in protecting vision. The macular pigment is made up exclusively of the carotenoids lutein and zeaxanthin. These two plant pigments, known as xanthophylls, are found in a variety of foods, mostly green, yellow, and orange fruits and vegetables. Egg yolks are also a source of highly bioavailable xanthophylls. Clinical studies have consistently shown that an increase in dietary intake of xanthophylls leads to an increased macular pigment density. Results from epidemiological studies, however, have been inconsistent in demonstrating the association between dietary intake of plant xanthophylls, serum concentrations, and macular pigment density. No population studies to date have included eggs as a dietary source of lutein and
zeaxanthin. The objective of the present study is to determine whether or not there is an association between egg consumption, lutein intake and central vision loss among community-dwelling older adults at risk for age-related macular degeneration (AMD). Egg intake was assessed with a survey questionnaire validated for content by older adults native to Kansas. Subjects were recruited from voter registration lists, newspaper advertisements, and local contacts. A total of 612 women and men provided responses for known and potential risk factors for macular degeneration in addition to the food items. Macular degeneration was ascertained by self-report in response to the question: Has your eye doctor ever told you that you have age-related macular degeneration? Individuals, rather than eyes, were the category of analysis for the outcome variable. Subjects who reported a diagnosis of macular degeneration (n=105) compared to subjects who reported no changes in the macula (n=507) were older
(75+ years), had a known family history of macular disease, had a history of high cholesterol, and were farsighted. After adjusting for these four independent risk factors, none of the egg intake variables showed a significant inverse trend with higher consumption. There was a modest reduced risk of macular degeneration (OR:0.80; 95% CI:0.41,1.54) in the upper 25% level of total egg intake. These exploratory data suggest that reversing the trend of decreased consumption of eggs and egg products may provide a protective effect on age-related macular degeneration. The biologic plausibility exists for the role of egg yolks in increasing macular pigment density, which may provide protection from damage to the photoreceptors critical to central vision. The initial finding from our analysis of no relationship between dietary egg intake and central vision loss may be mediated by the relatively limited egg intake in our study participants. The next phase of the project will involve
calculations and an in-depth analysis of the lutein content of the selected egg food items and additional data collection on other food sources of xanthophylls from a sub-sample of study participants.
Impacts
The purpose of this project is to assess the consumption of eggs and egg products and to estimate the total lutein intake. The results of this study will be a first step in gathering evidence of eggs as a nutritionally dense, high quality, inexpensive source of carotenoids needed to produce the macular pigment. Increasing the density of the pigment may aid in protecting the macula from damage and thereby reduce the risk of central vision loss in older adults.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
Loss of central vision in older adults is caused by a degenerative process in the macula of the human eye retina. The exact pathogenesis of this condition is unknown, but it appears from recent research that the macular pigment may play a role in protecting vision. The macular pigment is made up exclusively of the carotenoids lutein and zeaxanthin. These two plant pigments, known as xanthophylls, are found in a variety of foods, mostly green, yellow, and orange fruits and vegetables. Egg yolks are also a source of highly bioavailable xanthophylls. Clinical studies have consistently shown that an increase in dietary intake of xanthophylls leads to an increased macular pigment density. Results from epidemiological studies, however, have been inconsistent in demonstrating the association between dietary intake of plant xanthophylls, serum concentrations, and macular pigment density. No population studies to date have included eggs as a dietary source of lutein and
zeaxanthin. The objective of the present study is to determine whether or not there is an association between egg consumption, lutein intake and central vision loss among community-dwelling older adults at risk for age-related macular degeneration (AMD). A cross-sectional sampling of adults age 65 and older was conducted in six counties in central Kansas. These six counties were selected to represent the three highest and three lowest counties in the prevalence of AMD among Medicare beneficiaries. The majority of subjects (69%) were randomly selected from voter registration lists, with the remaining subjects being recruited at senior centers (19%) or from referrals (12%). The questionnaire developed for the study contained 31 items assessing both frequency and amount of intake of whole eggs and egg products. The sample analyzed to date consists of 627 study participants, including 110 subjects who reported a physician diagnosis of AMD. The study participants are primarily female (63%)
and white, not Hispanic (97%), The average age of the group is 76.1 years. Data analysis is being conducted by using binary logistic regression, controlling the confounding variables of age, heart disease, and high cholesterol as predictors of egg intake. Preliminary results indicate no association between total egg intake in servings per week and AMD status. Frequencies of dietary intakes of whole eggs and egg products separately are also not associated with AMD diagnosis. The biologic plausibility exists for the role of egg yolks in increasing macular pigment density, which may provide protection from damage to the photoreceptors critical to central vision. The initial finding from our analysis of no relationship between dietary egg intake and central vision loss may be mediated by the relatively limited egg intake in our study participants. The next phase of the project will involve calculations and an in-depth analysis of the lutein content of the selected egg food items and
additional data collection on other food sources of xanthophylls from a sub-sample of study participants.
Impacts
The purpose of this project is to assess the consumption of eggs and egg products and to estimate the total lutein intake. The results of this study will be a first step in gathering evidence of eggs as a nutritionally dense, high quality, inexpensive source of carotenoids needed to produce the macular pigment. Increasing the density of the pigment may aid in protecting the macula from damage and thereby reduce the risk of central vision loss in older adults.
Publications
- Allen, C 2004. Egg consumption and age-related macular degeneration: A pilot study. PhD Dissertation, Kansas State University.
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Progress 01/01/03 to 12/31/03
Outputs
A questionnaire was developed with 15 items on consumption of eggs and egg products plus an additional 23 items in the non-diet section. The format of the diet section is a semi-quantitative food frequency questionnaire containing the name of the food item, frequency of consumption, and portion size consumed. The independent variables of interest are age, gender, sunlight exposure, birth weight, smoking history, iris color, medical conditions, medication use, and supplement use. The survey form was reviewed with experts in nutrition and aging and pilot tested with volunteer adults age 65 years and older. Revisions were made to increase clarity and specificity of the items. Press releases, posters, and letters to agencies serving older adults in the six target counties were used to advertise the study and recruit participants. To date subjects have been recruited by self referral (12.7%), on-site visits to senior centers (32.0%), mailings to registered voters (46%),
referrals from county Extension leaders (5.3%), and snowballing techniques (4.0%). Data collection has been completed in two of the six counties. Completed questionnaires come from 219 women (73%) and 81 men (27%). Respondents range in age from 65 to 99 years (mean = 77 years). Fifty-seven respondents have been told by a physician that they have age-related macular degeneration (AMD) with 41 of them experiencing central vision loss due to AMD. Ninety-five percent of the first respondents are of European ancestry with light skin complexion.
Impacts
The purpose of this project is to assess the consumption of eggs and egg products and to estimate the total lutein intake. The results of this study will be a first step in gathering evidence of egg consumption as a nutritionally dense, high quality, inexpensive source of carotenoids needed to produce the macular pigment. Increasing the density of the pigment may aid in protecting the macula from damage and thereby reduce the risk of central vision loss in older adults.
Publications
- No publications reported this period
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