Journal Name:
J. Am. Coll. Nutr.
Article Title:
Dietary Linolenic Acid Intake Is Positively Associated with Five-Year Change in Eye Lens Nuclear Density.
Date Written:
2007
Volume:
26
Number:
2
Page:
133
Author(s):
Lu, M.; Taylor, A.; Chylack, Jr., L.T.; Rogers, G.; Hankinson, S.E.; Willett, W.C.; Jacques, P.F.
Article:
Cataract is the leading cause of low vision, responsible for approximately 50% of bilateral vision worse than 6/12 (20/40) among white, black, and Hispanic persons in the US [1]. An estimated 20.5 million (17.2%) Americans older than 40 years have cataract in either eye [2]. The number of Americans affected by cataract and undergoing cataract surgery will dramatically increase over the next 20 years as the US population ages. 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 [3– 6]. There has been little epidemiological research on dietary fat intake and risk of cataract. In previous research, this group indicated that 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 [9]. In the present study conducted in this same group of women, we examine relationship between dietary fat intake and the change in nuclear lens opacification over a five-year follow-up period.
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.
The data revealed that the 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. 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 There were no significant associations between other dietary fats and change in nuclear density.
The authors note that the ALA association may be spurious as these findings show discrepancies with earlier cross-sectional observations and the prospective observations from the full Nurses Health Study. Differences in sample size and follow-up time also might contribute to the discrepancy. In addition, an association between linoleic acid and nuclear opacities was not seen in the present study, an association that was observed in earlier work. Since vegetable oils and margarines are the best source for both linoleic and ALA, our 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. There could be misclassification of linoleic acid and ALA for women who don’t always use the same type of oil or margarine, limiting the ability to identify specific associations with these two fatty acids. In this study sample, linoleic acid and linolenic acid intakes were strongly correlated.
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.
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