The risk of cataracts appears to diminish among those who regularly eat spinach and those who have taken vitamin C supplements for more than 10 years.

These were the main findings of a long term survey by Harvard Medical School among 50,000 women across 11 states of the US.

Surgery to remove cataracts accounts for 12 per cent of the US Medicare budget. Delaying the onset of cataracts by 10 years could reduce the need for surgery by 45 per cent.

It was against this backdrop that the survey was started in 1980 among female registered nurses over the age of 45; others were included as they reached that age.

During the survey period, 493 cataracts were removed. Those in the study group who took regular doses of vitamin A had a 39 per cent lower risk of developing cataracts. Among the food groups, those who regularly ate spinach also seemed to face lower risk of developing cataracts, although no evidence seemed to support the remedy of folklore that carrots could improve the eyes.

The risk was also low among those who regularly took vitamin C for 10 years or more, although this was not so among those who took vitamin C as part of a multivitamin. The beneficial effects of vitamin C were particularly strong among those who have never smoked.

The study team said their findings lend support to the antioxidant hypothesis of cataract prevention. British Medical Journal, 8 August 1992.

Another study has shown that smoking cigarettes substantially increases the risk of developing cataracts in later life.