Cataract: New evidence that antioxidants support lens health

Cataract are the clouding of the eye's lens that develops gradually over time. They have been linked to a number of factors including age, diet and sun exposure.

A number of studies over the past decade have suggested that antioxidant vitamins might reduce the risk of age-related cataract. For example the Vision and Nutrition Project found that long-term use (ten years or more), of antioxidants like vitamin C, reduces cataract risk (1). Other studies have noted risk reduction in people with higher blood levels of vitamin E (2). Recent studies have also linked lutein, rather than beta-carotene, to reduced risk (3).

Since early cataract probably begins at about age 45, some experts believe that people in their 30s and 40s can delay the onset or progression of lens clouding by consuming more fruits and vegetables or taking antioxidant supplements. Now a new study called REACT (4), lends considerable support for that belief.

In REACT, or the Roche European and American Cataract Trial, 297 patients were randomized to one of three clinical centers in Boston, Bradford and Oxford England. The volunteers received placebo or the antioxidants vitamins C, E and beta-carotene, and were followed, on average, for three years. To assess how much their cataracts were progressing, the investigators measured the increase in the area of cloudiness.

When the antioxidant takers in both countries were compared to all placebo takers, a significant reduction in the progression of lens clouding was found in the group getting vitamins. The beneficial effect was more pronounced when looking only at the US participants, particularly in those who had early or no cataract to begin with. However in their British counterparts, whose cataracts were generally more advanced at the study's start, antioxidant and placebo groups were not significantly different.

While the slowing in cataract progression among the antioxidant takers was modest, it could be very important in the long term, according to the authors. The extent of lens clouding was 1.6% less in the antioxidant treated group over the three-year period. At that rate, if antioxidants were taken over ten to twenty years it would translate to a clinically important 5-10% reduction in lens clouding, a slowing that could have a sizable impact on the need for cataract surgery.

References

1. Taylor A et al. Long-term intake of vitamins and carotenoids and odds of early age-relate cortical and posterior subcapsular lens opacities. Am J Clin Nutr; 75:540-49, 2002
2. Lyle BJ et al. Serum carotenoids and tocopherols and incidence of age-related cataract. Am J Clin Nutr; 69:272-7, 1999
3. Chasan-Taber et al. A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women. Am J Clin Nutr; 70:431-2, 1999
4. The REACT Group. The Roche European American Cataract Trial (REACT): A randomized clinical trial to investigate the efficacy of an oral antioxidant micronutrient mixture to slow progression of age-related cataract. Ophthalmic Epidemiology; 9:49-80, Feb. 2002