Measles, one of the six major childhood diseases, rapidly reduces blood levels of vitamin A and frequently precipitates xerophthalmia. Retinol is chiefly found in milk, butter, cream, cheese, egg yolk, liver, kidneys and some of the fatty fish. Carotene is widely distributed among plant foods. It is found in green vegetables in association with chlorophyll, so that the green outer leaves of vegetables like cabbage and lettuce are good sources of carotene, while the inner leaves contain little or none. Other useful sources are yellow and red fruits and vegetables.
All vegetable oils are devoid of vitamin A activity with the exception of red palm oil.
Sufficient vitamin A-rich foods are often not available in some communities, particularly at certain times of the year. In other situations, vitamin A-rich foods may be available in the community but not be consumed in sufficient quantities by certain families for economic or cultural reasons, or they may be available in the family but not be eaten by young children or pregnant or lactating women. The whole question of vitamin A deficiency, the key resources in its prevention and elimination, the whole problem and the solution, has been studied in the past fifty years in detail globally. Even today more than a quarter of a million children six months to six years of age are estimated to go blind every year due to a deficiency of vitamin A, and some 14 million currently exhibit signs of clinical xerophthalmia ranging from dryness to severe ulceration's. Today people simply could not imagine how a poor man towards the end of the 1840's was starving there during his life.