Dietary Linolenic Acid Intake Is Positively Associated with Five-Year Change in Eye Lens Nuclear Density
Dietary Linolenic Acid Intake Is Positively Associated with Five-Year Change in Eye Lens Nuclear Density
Year: 2007
Authors: Lu, M. Taylor, A. Chylack, Jr., L.T. Rogers, G. Hankinson, S.E. Willett, W.C. Paul F. Jacques, P.F.
Publication Name: Journal of the American College of Nutrition
Publication Details: Volume 26; Number 2; Pages 133�140.
Abstract:
Dietary fat may affect lens cell membrane composition and function, which are related to age-related cataract. The present study was designed to examine the associations between dietary fat and the change in nuclear lens opacification over five years. Women aged 52 to 73 years without previously diagnosed cancer, diabetes and cataracts from the Boston, Massachusetts area were selected from the Nurses� Health Study cohort. Four hundred forty women participated in a baseline (1993�95) and a follow-up (1998�2000) eye examination. Intakes of total fat and selected fatty acids were calculated as the average intake from five food frequency questionnaires that were collected between 1980 and baseline. Change in the degree of nuclear density (opacification) was characterized by the difference between baseline and follow-up in pixel density at the central clear zone in the Scheimpflug slit image of the lens. Intake of alpha-linolenic acid (ALA) was positively associated with change in nuclear density. The geometric mean nuclear density change was 16% greater in the highest quartile category of ALA intake than in the lowest quartile category (P for trend< 0.05). For women in the high tertile category of baseline nuclear lens opacification, the geometric mean change in the highest quartile category of ALA acid intake was 70% higher than the change in the lowest quartile category (P for trend< 0.01). There were no significant associations between other dietary fats and change in nuclear density. Higher ALA intake was associated with a greater age-related change in lens nuclear density. (Author's abstract)
Cataract is the leading cause of low vision, with an estimated 20.5 million (17.2%) Americans older than 40 years experiencing one in either eye. The composition, structure and function of cell membranes are affected by dietary fat, while the development of cataract is associated with changes in the composition of the lens fiber cell membranes. A high level of polyunsaturated fatty acids in the diet has been reported to delay the development of advanced cataracts in animal studies. There has been little epidemiological research on dietary fat intake and risk of cataract. The prevalence of newly diagnosed, age-related nuclear opacities was positively associated with alpha-linolenic and linoleic acid intake in a subset of women from the Nurses� Health Study cohort. In the present study conducted in this same group of women, the relationship between dietary fat intake and the change in nuclear lens opacification over a five-year follow-up period is examined. The results indicated that a higher intake of ALA was associated with a greater five-year increase in nuclear lens density. The geometric mean nuclear density change was 16% greater in the highest quartile category of ALA intake than in the lowest quartile category. The relationship was much stronger for women with a greater degree of nuclear lens opacification at baseline. ALA is easily oxidized because it contains many unsaturated bonds. Oxidative stress is a major contributor to cataract formation. Since vegetable oils and margarines are the best source for both linoleic and ALA, the ability to distinguish between linoleic acid and ALA intake is strongly dependent on the types of vegetable oil and margarine that the women reported that they usually use and this could introduce discrepancies in the reporting and thus the observations. There could be misclassification of linoleic acid and ALA for women who don�t always use the same type of oil or margarine. Although these findings suggest that ALA intake might contribute to the development or progression of nuclear lens opacities, the mechanism by which ALA might adversely affect the lens is uncertain since ALA is undetectable in cataractous as well as normal lenses with current instrumentation. In summary, the data from this study suggest a relationship between a higher intake of ALA and increased nuclear lens opacification. However, more studies are needed to verify this association and clarify the relationship between intake of other fatty acids and age-related cataract. (Editor's comments)
Cataract is the leading cause of low vision, with an estimated 20.5 million (17.2%) Americans older than 40 years experiencing one in either eye. The composition, structure and function of cell membranes are affected by dietary fat, while the development of cataract is associated with changes in the composition of the lens fiber cell membranes. A high level of polyunsaturated fatty acids in the diet has been reported to delay the development of advanced cataracts in animal studies. There has been little epidemiological research on dietary fat intake and risk of cataract. The prevalence of newly diagnosed, age-related nuclear opacities was positively associated with alpha-linolenic and linoleic acid intake in a subset of women from the Nurses� Health Study cohort. In the present study conducted in this same group of women, the relationship between dietary fat intake and the change in nuclear lens opacification over a five-year follow-up period is examined. The results indicated that a higher intake of ALA was associated with a greater five-year increase in nuclear lens density. The geometric mean nuclear density change was 16% greater in the highest quartile category of ALA intake than in the lowest quartile category. The relationship was much stronger for women with a greater degree of nuclear lens opacification at baseline. ALA is easily oxidized because it contains many unsaturated bonds. Oxidative stress is a major contributor to cataract formation. Since vegetable oils and margarines are the best source for both linoleic and ALA, the ability to distinguish between linoleic acid and ALA intake is strongly dependent on the types of vegetable oil and margarine that the women reported that they usually use and this could introduce discrepancies in the reporting and thus the observations. There could be misclassification of linoleic acid and ALA for women who don�t always use the same type of oil or margarine. Although these findings suggest that ALA intake might contribute to the development or progression of nuclear lens opacities, the mechanism by which ALA might adversely affect the lens is uncertain since ALA is undetectable in cataractous as well as normal lenses with current instrumentation. In summary, the data from this study suggest a relationship between a higher intake of ALA and increased nuclear lens opacification. However, more studies are needed to verify this association and clarify the relationship between intake of other fatty acids and age-related cataract. (Editor's comments)
