Age related cataracts are responsible for 48% of blindness worldwide, a figure that represent around 20 million people. Cataracts are characterised by a clouding of the lens of the eye which occurs over time, and this eventually causes obstruction of view. Cataract surgery rose 10-fold between 1968 and 2003, which was caused largely by improvements in surgical techniques that lessened the time and risk associated with the operation. Diabetes, smoking and exposure to ultraviolet light are known risk factors for the development of cataracts, but evidence suggest that this risk can be reduced by diet. In particular, consumption of plant produce which are rich sources of carotenoids, vitamin C, vitamin E and other antioxidants may modulate the risk downwards by preventing the free radical damage thought to cause the clouding of the lens seen in cataract formation.
Because they eat more plant products and generally have higher levels of plant based antioxidants in their diets, vegetarians have a lower risk of cataracts when compared to non-vegetarian counterparts. For example, researchers1 have investigated the association between diet and cataracts in 27 670 non-diabetic subject age ≥40 years. Amongst the subjects studied, there was a 5.4% incidence of cataracts (1484 subjects). The results show a progressive reduction in the risk of developing cataracts from high meat eaters (50 to 99g meat/d) to low meat eaters (<50g meat/d), followed by fish eater, vegetarians and then vegans, with multivariate adjustment showing the incident ratios to be 0.96, 0.85, 0.79, 0.70 and 0.60, respectively. There was a 50% greater chance of developing cataracts amongst those subjects smoking 15 or more cigarettes a day, which supports findings from previous studies.
These results suggest that vegans and vegetarians are protected from developing cataracts by their diet. In particular it is thought that the xanthophylls lutein and zeaxanthin are able to reduce the risk of cataracts. These carotenoids are know to accumulate within the eye where they filter out the longer blue wavelength light and thus protect the eye. This is the same role that they perform in plants, where they protect from overexposure to damaging ultraviolet radiation. However in this study, carotenoids were not associated with protection from cataracts, as has been reported in many previous studies. Interestingly, retinol intake was associated with an inverse risk, and high retinol intakes are know to increase plasma levels of carotenoids, by sparing conversion to vitamin A. Taken as a whole these results support the hypothesis that increases in carotenoid antioxidants are protective of cataracts probably through an antioxidant action.
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