Researchers concluded that genetic factors account for about 35 per cent of the difference in cataract progression, while environmental factors like diet account for 65 per cent. “We found no beneficial effect from supplements, only from the vitamin C in the diet,” says Dr Christopher Hammond, an author of the study, published in Ophthalmology. Foods high in vitamin C include oranges, cantaloupe, kiwi, broccoli and dark leafy greens.