The Nutrition and Vision Project

The Nutrition and Vision Project (NVP) is an ongoing collaboration between the Nutritional Epidemiology Program at the USDA Center at Tufts, the Center for Ophthalmic Research at Brigham and Women's Hospital at Harvard, and the Nurses' Health Study at Harvard.

Findings from the NVP research team over the years strongly suggest that antioxidants provide protection against nuclear and cortical opacity (1). They have observed, for example, that:

• Intake of vitamin C of 300 mg/ day provides benefit over intake of 140 mg/day (although the latter is twice the RDA).
• For women under 60, use of vitamin C supplements for at least 10 yrs was associated with 60% decreased odds for cortical cataract.
• Onset or progression of cataract over 5 years is diminished 29% in users of vitamin E supplements for 10 years or more.

In a new study, the NVP reports that long-term vitamin E supplementation and higher intake of several B-vitamins may reduce cataract progression (2).

Study Design

The present study examines the change in nuclear lens opacity during a 5-year follow-up period in women aged 52 to 74. Nutrient intake was determined from multiple food frequency and supplement use questionnaires. The degree of nuclear density (opacification) was assessed using computer-assisted analysis of digital lens images.

Results

The median 5-year change in nuclear density of 18 was positively correlated with amount of opacity at baseline (p< .001). Geometric mean 5-year change in nuclear density was inversely associated with the intake of riboflavin (p trend = .03) and thiamin (p trend = .04). However, the strongest inverse correlation was between change in nuclear density and length of vitamin E supplement use (p trend = .006). The increase in nuclear density among women who never used vitamin E supplements was 42% higher than for those who used vitamin E supplements for 10 or more years (Table 1).

Summary

The authors conclude: "Our observation that vitamin E intake is associated with a reduction in nuclear opacification is consistent with other longitudinal studies and strengthens the hypothesized role for this specific nutrient in nuclear cataract formation".

Discussion

The authors offer several possible explanations as to why the inverse association between vitamin C intake and cataract seen previously was not observed in this study. First, women who did not use vitamin C supplements and had a greater risk of increased nuclear density were, unfortunately, excluded from the analyses. Secondly, different nutrients may influence the process of lens opacification at different stages. Previous studies examined very early opacities, while the current study largely examined their progression. Vitamin C may help protect lens crystallins from initial insults, while vitamin E and other nutrients seem to act at a later stage, perhaps protecting lens membranes against damage.

Table 1. Relation Between 5-Year Change in Nuclear Density and Duration of Vitamin Supplement Use* Duration of Supplement Use               Supplement None† 1-4y 5-9y ≥10y   P  Trend Vitamin C               Mean 17.7 18.5 19.2 16.6     95% Confidence Interval 13.9-21.9 14.4-23.0 14.2-24.8 12.2-21.6 .58   Sample Size 221 96 40 50                 Vitamin E               Mean 17.9 18.1 16.6 12.6     95% Confidence Interval 14.1-22.2 14.2-22.5 11.8-22.1 8.2-17.6 .006   Sample Size 261 87 31 29                 Multivitamin               Mean 18.2 17.1 18.5 17.8     95% Confidence Interval 14.2-22.8 13.1-21.6 14.3-23.2 13.8-22.3 .93   Sample Size 134 86 73 115

*Geometric 5-year change in mean nuclear density measured as pixel density units adjusted for age at examination, smoking at baseline, body mass index at baseline, summertime sunlight exposure in 1980, usual alcohol intake at baseline, nuclear density at baseline, & length of follow-up. † No or <1yr use of supplement

References

1. Jacques PF et al. Long-term nutrient intake and early age-related nuclear lens opacities. Arch Ophthalmol 119:1009-19, 2001
2. Jacques PF et al. Long-term nutrient intake and 5-year change in nuclear lens opacities. Arch Ophthalmol 123:517-26, 2005.