Although numerous studies show vitamin A intake can affect various aspects of ocular health, little is known about how it may influence myopia. A prospective study published in Translational Visual Science & Technology explores the relationship of dietary vitamin A and myopia.
The research reviewed the cases of 642 participants in Western Australia.. The investigation employed data from Australia’s parent-child Raine Study Gen2, which follows children from the second trimester of gestation (generation 2) to adulthood. Adolescents’ diet was evaluated with retrospective yearly food questionnaires at 14, 17, and 20 years of age, and ocular function was assessed using post-cycloplegic autorefraction at about 20 years of age. Other tests included axial length, central corneal and retinal thickness, and conjunctival ultraviolet autofluorescence (CUVAF). Right eye measurements were analyzed.
Vitamin A-equivalent data was compared with the 20-year ophthalmic assessment. Results demonstrated young adults whose vitamin A intake was sufficient had less risk for myopia (P =.03), but after adjusting for potentially confounding factors such as parental myopia, the link became less impactful (P =.06).
At year 14, 5.8% of the sample displayed low vitamin A intake of fewer than 600 μg per day. At year 17, 16.7% had low consumption; and at year 20, 69.3% were classified low in vitamin A. Of individuals with low intake at 14 years of age, 29.7% developed myopia. At 17 years of age, 23.4% of those with fewer than 600 μg per day developed myopia; and at 20 years of age, 27.4% of participants classified as low in this nutrient displayed myopia.
Investigators did not find significant linear correlations between spherical equivalent refractive errors and total vitamin A at years 14 and 17. Similarly, researchers noted no significant correlations between refractive error and vitamin A at year 20 (P =.14), but they did note “significant negative association between the myopic group and low vitamin A intake category,” (P =.01).
Correlations between axial length and vitamin A were insignificant. While no reported associations involved carbohydrates, zinc intake, or highest educational level at year 20, investigators did see correlations between myopia and the factors CUVAF (P <.001), and parental history (P =.001).
Questionnaires were used to estimate quantity, in μg, of retinol consumption from animal foods, alpha carotene and beta carotene-equivalent from plants, and total dietary vitamin A. Survey data was based on recall. Serum levels that could reflect certain types of genetic tendencies such as retinoic acid metabolism were not measured — a limitation of this study. Also, the sample was relatively lacking in the lower ranges of vitamin A intake. Strengths of the analysis included an established longitudinal cohort, with data for CUVAF and parental history, allowing for statistical adjustment.
“Although the link between myopia and vitamin A does not appear to be linear, a threshold may exist for optimal vitamin A intake and axial elongation,” according to the study.
Ng FJ, Mackey DA, Sullivan TA, et al. Is dietary vitamin A associated with myopia from adolescence to young adulthood? Trans Vis Sci Tech. 2020;9(6):29. doi:10.1167/tvst.9.6.29.