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We read with interest the letter published by Vu et al1 which investigated the risk of age related macular degeneration (AMD) and its association with the dietary carotenoids, lutein and zeaxanthin (LZ), stratified by linoleic acid intake. Vu et al reported a marked increase in the risk of both early and late AMD among people who consumed greater than the median intake of linoleic acid and higher dietary intakes of LZ.
We have a number of concerns in relation to the authors’ letter and their conclusions. The letter used cross sectional data based on photographic macular assessments of 71.9% of their sample of 2448 people, who attended follow up examinations. The authors also included 212 people who did not have photographic macular assessment (10.8% of those with dietary assessments). This is one area of concern. The dietary assessment method (food frequency questionnaire, FFQ) was not conducted at baseline, which only allows …