Deficiencies of Vitamin A

The fat-soluble vitamin A is necessary for the synthesis of rhodopsin, a light-sensitive pigment in your retina. Vitamin A also keeps your skin healthy and contributes to the structure of the mucus membranes in your intestinal tract, lungs and kidneys. Deficiencies of vitamin A are a health problem in more than half of all countries, according to the World Health Organization.

Cause of Deficiency

Vitamin A deficiency is classified into two types based on the cause. Primary vitamin A deficiency is a type of deficiency caused by an extended period of inadequate dietary intake of vitamin A. Secondary vitamin A deficiency is a type of vitamin A caused by decreased availability or absorption of vitamin A. Decreased availability and absorption may occur as a result of celiac disease, cystic fibrosis, chronic diarrhea, bile duct obstruction or cirrhosis.

Symptoms

One of the earliest signs of a vitamin A deficiency is a decreased ability to see at night, or night blindness. As vitamin A deficiency worsens, it can lead to extreme dryness and damage to the cornea, a condition referred to as xerophthalmia. Xerophthalmia can lead to blindness, and according to "Nutrition and You" by Joan Salge Blake, is the leading cause of preventable blindness in children.

Vitamin A deficiency can also result in dry skin and thickening or scaling of the skin. Mucus membranes may also not form properly, which increases your susceptibility to infections.

Treatment

Treatment for vitamin A deficiency depends on the cause. Primary vitamin A deficiency can usually be corrected with oral supplementation with vitamin A. Oral supplementation can also increase vitamin A levels in those with secondary vitamin A deficiency, but further treatment is also needed for the underlying condition in order to prevent a recurrence.

Prevention

In order to prevent vitamin A deficiency due to a lack of sufficient dietary intake, it is important to meet your vitamin A requirements every day. Adult women should consume 700 mcg of vitamin A daily, whereas adult men should consume 900 mcg of vitamin A every day.

The best food sources of vitamin A include milk, cereals, egg, cheese, carrots, sweet potatoes, spinach and organ meats, such as liver. "Nutrition and You" by Joan Salge Blake notes that consuming foods that are rich in vitamin A with a tablespoon of vegetable oil can increase their absorption.