Earlier EduFacts issues have reviewed evidence of the inverse relationship between decreased rates of lens opacities and/or cataract extraction and higher overall intake (supplements and/or food intake) of the anti-oxidative vitamins E and C. In this report, data supporting the value of vitamin A in cataract prevention are presented.

Vitamin A, or retinol, is part of the visual pigment in the human eye, protecting the retinal epithelium. The importance of vitamin A with respect to retinal health is well known; severe vitamin A deficiency is a leading cause of blindness among under-nourished populations. However, it is sometimes overlooked that vitamin A, as an anti-oxidant, is also of value in preventing lens opacities. The Lens Opacities Case-Control Study (1), the Nutritional Factors in Eye Disease Study (part of the Beaver Dam eye Study) (2), and the Nurses' Health Study (3), provide evidence of decreased risk of lens opacities associated with increased vitamin A intake.

In the Case-Control study (1) patients with opacities were compared with controls with respect to level of vitamin A obtained through supplements on a regular basis (at least once a week for at least a year). Increased vitamin A intake was associated with a 55% decrease in cortical opacities and a 40% decrease in mixed opacities (adjusted for age and sex).

In the Nutrition and Eye Disease Study (2) moderate levels of vitamin A intake were associated overall with a 40% decreased risk of nuclear sclerotic opacity (p=0.002). This risk was adjusted for age, sex, smoking, and heavy drinking. Among smokers, risk of cataract was reduced 50%.

In the Nurses' Health Study (3), a large cohort of nurses has been followed for almost 20 years. In this longitudinal study increased dietary intake of vitamin A was associated with a 39% reduction in risk of cataract extraction.

References

1. Leske MC, Chylack LT Jr, Wu S. The lens opacities case-control study:risk factors for cataract. Arch Ophthalmol 1991;109:244-251.
2. Mares-Perleman JA Klein BEK, et al. Relationship between lens opacities and vitamin and mineral supplement use. Ophthalmology 1994;101:315-325.
3. Hankinson SE, Stampfer MJ et al. BMJ volume 305, 1992