Age-related cataract is an important public health problem because approximately 50% of the 30-50 million cases of blindness worldwide result from leaving the condition untreated (Jacques 1999). The mechanisms that bring about a loss in transparency include oxidation, osmotic stress, and chemical adduct formation (Bunceetal 1990). Besides traditional risk factors such as diabetes, nutrient deficiency is also being considered, particularly those with antioxidant properties.
Cataract was shown to be associated with riboflavin deficiency in animals in the 1930s and subsequently with deficiencies of amino acids, vitamins and some minerals (Wynn & Wynn 1996). This has been confirmed in human studies whereby lens opacities have been associated with lower levels of riboflavin, vitamins A, C and E, iron, and protein status (Leske et al 1995, Mares-Perlman et al 1995).
Glutathione reductase is a key enzyme involved in lens protection. Riboflavin levels indirectly influence glutathione reductase activity, increasing the lens's ability to deal with free radical formation (Head 2001). One study documented severe glutathione reductase deficiency in 23% of human lens-epithelium specimens, possibly reflecting a dietary deficiency of riboflavin (Straatsma et al 1991). Another study identified that a significant number of people with cataracts have inactive epithelial glutathione reductase (Horwitz et al 1987).
A large cross-sectional survey of 2873 volunteers aged 49-97 years detected a link between dietary vitamin supplement and a lower incidence of both nuclear and cortical cataract. Vitamin A, niacin, riboflavin, thiamine, folate and vitamin B12 all appeared to be protective, either in isolation or as constituents of multivitamin preparations (Kuzniarz et al 2001).
A recent sample of 408 women from the Nurses' Health Study aged 52-74 years at baseline participated in a 5-year study that assessed nutrient intake and the degree of nuclear density (opacification). Findings revealed that the geometric mean 5-year change in nuclear density was inversely associated with the intake of riboflavin (P = 0.03) and thiamin (P = 0.04), and most significantly with the duration of vitamin E supplement use (P = 0.006) (Jacques et al 2005).
The evidence currently suggests that higher intakes of riboflavin are protective against the progression of age-related lens opacification.
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