Vitamin A (retinol) is necessary for the function of light-sensitive nerve cells (photoreceptors) in the eye’s retina and thus helps maintain night vision. It also helps keep the skin and the lining of the lungs, intestine, and urinary tract healthy and protects against infections. Good sources of vitamin A include fish liver oils, liver, egg yolks, butter, cream, and fortified milk. (See also Overview of Vitamins Overview of Vitamins Vitamins are a vital part of a healthy diet. The recommended dietary allowance (RDA)—the amount most healthy people need each day to remain healthy—has been determined for most vitamins. A safe... read more .)
Carotenoids, such as beta-carotene, are pigments in fruits and vegetables that give them their yellow, orange, or red color. Once consumed, carotenoids are slowly converted to vitamin A in the body. Carotenoids are best absorbed from cooked or homogenized vegetables served with some fat or oil. Good sources of carotenoids are dark green, yellow, and orange vegetables and yellow and orange fruits.
Vitamin A deficiency is usually caused by
This deficiency is common in areas of the world where people do not eat enough of foods that are good sources of vitamin A, such as
For example, vitamin A deficiency occurs in southern and eastern Asia, where regular rice, which contains no vitamin A, is the main food. Golden rice has higher amounts of beta carotene, and may decrease vitamin A deficiency.
Disorders that impair the intestine’s absorption of fats can reduce the absorption of the fat-soluble vitamin A and increase the risk of vitamin A deficiency. These disorders include chronic diarrhea Diarrhea in Adults Diarrhea is an increase in the volume, wateriness, or frequency of bowel movements. (See also Diarrhea in Children.) The frequency of bowel movements alone is not the defining feature of diarrhea... read more , celiac disease Celiac Disease Celiac disease is a hereditary intolerance to gluten (a protein found in wheat, barley, and rye) that causes characteristic changes in the lining of the small intestine, resulting in malabsorption... read more , cystic fibrosis Cystic Fibrosis (CF) Cystic fibrosis is a hereditary disease that causes certain glands to produce abnormally thick secretions, resulting in tissue and organ damage, especially in the lungs and the digestive tract... read more , certain pancreatic disorders, and blockage of the bile ducts The liver produces bile, a greenish yellow, thick, sticky fluid. Bile aids digestion by making cholesterol, fats, and fat-soluble vitamins easier to absorb from the intestine. Bile also helps... read more . Surgery on the intestine or pancreas can have the same effect.
Liver disorders Overview of Liver Disease Liver disease can manifest in many different ways. Characteristic manifestations include Jaundice (a yellowish discoloration of the skin and whites of the eyes) Cholestasis (reduction or stoppage... read more can interfere with the storage of vitamin A. (Most of the body's vitamin A is stored in the liver.)
Vitamin A deficiency is common among people who have had a severe deficiency of protein and calories (protein-energy undernutrition Protein-Energy Undernutrition Undernutrition is a deficiency of calories or of one or more essential nutrients. Undernutrition may develop because people cannot obtain or prepare food, have a disorder that makes eating or... read more ) for a long time. People with this disorder do not consume enough vitamin A, and storage and use of vitamin A is impaired.
An early symptom of vitamin A deficiency is night blindness, which is caused by a disorder of the retina. Soon thereafter, the whites (conjunctiva) and corneas of the eyes may become dry and thick—a condition called xerophthalmia Keratomalacia Keratomalacia is an eye disorder that involves drying and clouding of the cornea (the clear layer in front of the iris and pupil) due to vitamin A deficiency in people with undernutrition. Vitamin... read more . Xerophthalmia is particularly common among children who have a severe deficiency of calories and protein, which includes inadequate intake of vitamin A. Foamy deposits (Bitot spots) may appear in the whites of the eyes. The dry cornea may soften and deteriorate, and blindness may result. Vitamin A deficiency is a common cause of blindness in developing countries.
The skin becomes dry and scaly, and the lining of the lungs, intestine, and urinary tract thicken and stiffen.
The immune system Overview of the Immune System The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more does not function normally, making infections more likely, particularly in infants and children.
Children’s growth and development may be slowed. More than half of children with severe vitamin A deficiency may die.
Doctors suspect vitamin A deficiency based on symptoms, such as night blindness.
Doctors measure the level of vitamin A in the blood. However, levels do not decrease until the deficiency is severe because the body stores large amounts of vitamin A.
If people have problems seeing in the dark, eye tests, such as electroretinography Electroretinography A variety of tests can be done to confirm an eye problem or to determine the extent or severity of an eye disorder. Each eye is tested separately. In general, angiography involves injecting... read more , may be done to determine whether vitamin A deficiency is the cause.
To help confirm vitamin A deficiency, doctors may give people vitamin A supplements to see whether they relieve symptoms.
To help prevent vitamin A deficiency, people should eat dark green leafy vegetables, yellow and orange fruits (such as papayas and oranges), carrots, and yellow vegetables (such as squash and pumpkin). Other food sources include milk and cereals that are fortified with vitamin A, liver, egg yolks, and fish liver oils. The carotenoids that give fruits and vegetables their yellow, orange, or red color and that are converted to vitamin A in the body, are best absorbed from cooked or homogenized vegetables served with some fat or oil.
Children who live in developing countries and are at risk of vitamin A deficiency should take vitamin A supplements.