OCT 28, 2011
This large, population-based, cross-sectional study from the October issue of Ophthalmology examined the association between vitamin C and cataract in India. The authors collected data on socioecomonic and lifestyle factors, obtained blood samples and conducted clinical exams in 5,638 people age 60 and older. They found a strong association between vitamin C and cataract. The results also indicate that the population was vitamin C-depleted, which may explain in part the high levels of cataract in India.
Vitamin C was inversely associated with cataract. Inclusion of other antioxidants in the model (lutein, zeaxanthin, retinol, β-carotene and α-tocopherol) made only a small attenuation to the result (OR 0.68; 95% CI, 0.57–0.82; P < 0.0001). Similar results were seen with vitamin C by type of cataract: nuclear cataract (adjusted OR 0.66; CI, 0.54–0.80; P < 0.0001), cortical cataract (adjusted OR 0.70; CI, 0.54–0.90; P < 0.002) and posterior subcapsular cataract (PSC) (adjusted OR 0.58; CI, 0.45–0.74; P < 0.00003). Lutein, zeaxanthin and retinol were significantly inversely associated with cataract, but the associations were weaker and not consistently observed by type of cataract. Inverse associations were also observed for dietary vitamin C and cataract.
The authors believe this to be the first large population-based study to provide evidence from a low- or middle-income country on the relationship between vitamin C and cataract. They propose that the finding of gradients of risk across different levels of plasma vitamin C suggests there may be no clear threshold above which there is no additional benefit or adverse effect. However, they consider this concept tentative because of the relative paucity of studies investigating plasma vitamin C and cataract and the inconsistent findings from high-income countries.