Associations between nutrition and cataract.

Blindness due to opacification of the lens, or cataract, afflicts 50 million persons worldwide. In the United States over 541,000 cataract extractions are done annually at a cost of over $3.8 billion. Conservative estimates indicate that the prevalences of cataracts in Americans aged 65-75 and 75-85 years are 18% and 46%, respectively. Cataracts are even more prevalent in some other populations. It is estimated that the need for cataract extractions would be diminished by half if onset of cataract could be delayed by only ten years. Hypotheses regarding the etiology of cataract include oxidative perturbations of protein metabolism, diverse pathologic conditions, and perhaps glycation of lens proteins. Epidemiologic data indicate that elevated plasma levels of specific nutrients (i.e., carotenoids, ascorbate, tocopherol, and taurine) are associated with diminished incidence of certain types of cataract. Biochemical evidence suggests that each of these compounds can delay photooxidative damage to lens proteins. Roles in lens metabolism for selenium and tryptophan have been suggested. Elucidation of mechanisms by which caloric restriction delays cataract development is a promising area of current research.