A study using experimental animals found that vitamin E — as alpha-tocopherol, the most common form sold — protected the animals from radiation-induced cataracts.

In a human study, 175 people with cataracts were compared to 175 without cataracts, and researchers found that those with the highest vitamin E blood levels had a 50 percent lower risk of developing a cataract.

The Vitamin E and Cataract Prevention Study (VECAT) was a randomized trial that examined healthy volunteers ages 55 to 80 over a four-year period after being given either vitamin E or a placebo.

The researchers found that the vitamin E significantly protected against cortical cataracts but not nuclear cataracts — the type seen in most older people.

In a long-term study of 764 people, scientists reported a 30 percent reduction in lens clouding in subjects who took a daily multiple vitamin, along with a 57 percent reduction in regular users of vitamin E and a 42 percent reduction in those with high levels of vitamin E in their plasma.

Vitamin E is a powerful antioxidant and raises the glutathione level in the lens. The recommended dose is 500 IU a day as a mixed tocopherol (natural vitamin E).