Symptoms of vitamin A deficiency include night blindness, which can lead to permanent blindness in severe cases; increased susceptibility to infection; and skin problems. Vitamin A deficiency is common in developing nations but rare in developed countries. Those most susceptible in developed countries include those on strict diets and those who abuse alcohol. Alcohol abuse presents a one-two punch: alcohol depletes vitamin A stores, and alcoholics often have poor diets. Chronic diarrhea, iron deficiency, and any condition that interferes with nutrient absorption in general can lead to Vitamin A deficiency.
An excess of vitamin A can lead to liver problems, central nervous system disorders, and decreased bone density, and can also cause birth defects. It is impossible to overdose on vitamin A through consumption of plant products because the carotenoids in plants are an inactive form. The skin may turn orange due to storage of carotene by the body. Consumption of excessive amounts of liver, which contains large amounts of retinol, and of supplements can lead to overdose symptoms.
Liver is the most concentrated food source of vitamin A. Carrots and sweet potatoes are very high in beta carotene, and a single carrot exceeds the recommended minimum daily intake. Other foods that contain significantly less of the vitamin but that are nonetheless rich sources include kale, mangoes, spinach, papaya, red peppers, apricots, and cantaloupe. Since beta carotene is a yellow-orange pigment, it may be easy to remember that most foods this color (but not oranges) are high in beta carotene, as are dark green vegetables. Eggs and dairy products also contain vitamin A.