It takes an entire alphabet of nutrients to keep the body healthy, and the list begins with vitamin A. This important vitamin helps ensure that photoreceptors, or light-sensitive nerve cells in the eye's retina, function properly. Vitamin A is also important to the health of the skin, lungs, intestine, and urinary tract, and it helps prevent infection. Most people around the world get plenty of vitamin A through foods or multivitamins, but vitamin A deficiency is common in developing countries or in areas where people do not eat enough eggs or vegetables.
Problems with Vitamin A Absorption
While most cases of vitamin A deficiency come from inadequate nutrition, it can also be a side effect of certain health disorders. Conditions like celiac disease, cystic fibrosis, blockage of the bile ducts, and some pancreatic disorders can diminish the body's ability to metabolize fats, which impairs vitamin A absorption.
Related: Five Myths about Vitamins
Vitamin A Deficiency Symptoms
The first symptom of vitamin A deficiency is a reduced ability to see in dimmer light, or night blindness. If left untreated, foamy deposits called Bitot spots can form in the whites of the eyes, and people can develop xerophthalmia, a condition in which the whites and corneas of the eyes become thick and dry. Softening and deterioration of dry corneas can result in blindness. In fact, vitamin A deficiency is a common cause of blindness in developing countries.
Other vitamin A deficiency symptoms include:
- Dry, scaly skin
- Thickening of the lungs, intestine, and urinary tract
- Frequent infection
Sources of Vitamin A
There are two types of vitamin A: preformed vitamin A found in animal products and provitamin A found in fruits and vegetables. Foods that contain vitamin A include dairy products, organ meats, fortified breakfast cereals, salmon, leafy green vegetables, and orange and yellow produce like cantaloupe, apricots, mangoes, carrots, sweet potatoes, and squash.
Studies show that people who consume high amounts of plant-based vitamin A (but not vitamin A supplements) may reduce risks for lung or prostate cancer. On the flipside, smokers who consume high doses of vitamin A supplements actually can increase their risk of lung cancer.
Studies have found that vitamin A supplements can be valuable for deficient children in developing countries who contract the measles. High doses of the vitamin reduce fever and diarrhea caused by measles and lower risks for death from the disease.
Dangers of Excessive Vitamin A
Just as vitamin A deficiency can have negative effects on the body, so too can having an excessive amount of vitamin A levels. Side effects include cracked lips, dry skin, hair loss, headache, weak bones, and brain pressure. Getting vitamin A from food rather than supplements helps because the conversion process is very slow. However, if consumed in large quantities, carotenoids in orange and yellow fruits and vegetables can turn the skin yellow, particularly on the palms and soles of the feet.
Vitamin A is important to the human body in many ways. To maintain good health, it is important to get enough vitamin A, but too much can cause problems. People worried about vitamin A deficiency should see a medical professional for a blood test and treatment options.