Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily
Deficiencies of vitamin A in the United States are not common. However, up to half a million children each year in developing countries, particularly in Africa and Southeast Asia, become blind as a consequence of vitamin A deficiency. Professor Anding explains the symptoms of deficiency, as well as toxicity.
Vitamin A Deficiency
Both vitamin A toxicity and deficiency can affect fetal development. As early as 1937, research suggested that vitamin A deficiency in early pregnancy increased the risk of fetal deaths. Deficiency is linked with cell differentiation and the inability of these cells to become what they are genetically predetermined to be.
A vitamin A deficiency can occur from inadequate dietary intake or from the malabsorption of lipids, or fats. States of illness that might cause malabsorption of fat can be brought on by very, very low-fat diets, certain lipid-lowering medications, and chronic exposure to oxidants like cigarette smoke.
Some of the statin resins can have an impact on vitamin A status, as well as problems with bile. Bile keeps oil and water mixed together, emulsifying them so the fat can be better absorbed. Problems with bile production such as malabsorption of fat can lead to malabsorption of vitamin A.
The following health problems may result from a deficiency: reduced night vision, the inability to correct vision when going from a light room to a dark room, and the inability to correct vision when going from a lighted home to driving on a dark road at night. If the deficiency continues, it can cause the condition of night blindness.
A vitamin A deficiency also causes dry eyes or eye inflammation. In a condition known as Bitot’s spots, superficial white or gray patches occur on the eye membrane. Often in developing countries, when medical professionals look at the eyes of children who have a vitamin A deficiency, Bitot’s spots are one of the first things that they can assess.
Disease and Deficiency
A deficiency of vitamin A contributes to the high prevalence of measles seen in developing countries. This is because if you have a deficiency, you get a keratinization of the cells surrounding the GI tract, which allows bacteria and viruses to translocate or penetrate the barrier protecting your bloodstream.
According to the World Health Organization, 100 to 140 million children suffer from a vitamin A deficiency. This deficiency makes vitamin A blindness one of the leading causes of blindness in children worldwide.
“In my clinical practice, the only time I’ve ever seen a vitamin A deficiency is in someone who’s recently emigrated from a foreign country,” Professor Anding said. “I had a nursing student when I taught at the University of Texas whose whole family went blind from a vitamin A deficiency. When she saw pictures and slides in my class, she knew exactly what it was. She was living in Africa during the time of a massive famine, when fruits and vegetables, as well as animal sources of vitamin A, were in short supply.”
Vitamin A Toxicity
However, vitamin A can also be toxic when taken in excess. Toxicity is generally about 10 times the recommended dietary allowance (RDA), which is 900 micrograms for the average male and 700 for most females.
The tolerable upper limit is about 3,000 micrograms per day, or about 10,000 International Units. Usually a supplement bottle will tell you how many International Units are available in that product.
In the United States, we haven’t quite made the transition between micrograms and International Units. Twenty thousand International Units during pregnancy can cause birth defects and spontaneous abortion.
The most notable birth defects in pregnancy are cardiac birth defects, and that is one of the reasons why the formulations of prenatal vitamins have changed in the past few years. Prenatal vitamins used to only contain retinol, the active vitamin A. Now they’ve removed some of that and replaced it with beta-carotene, an antioxidant which converts to vitamin A.
Symptoms of vitamin A toxicity include blurred vision and painful swelling of the long bones such as the femur. It can also cause gynecomastia, or swelling of breast tissue in men.
“Early in my clinical practice. I had a lady who came into Tulane Medical Center in New Orleans, complaining of long bone tenderness,” Professor Anding said. “It wasn’t so much her joints were achy, but her bones were hurting. She wanted to know if there was any kind of dietary reason for that.”
At first, the medical team thought she had hyperparathyroidism, and they scheduled her for surgery. As they explored her diet more, they discovered that she was taking a lot of preformed vitamin A.
She actually had vitamin A poisoning, which was responsible for her long bone tenderness, rather than hyperparathyroidism. She stopped the supplement, and the pain went away.
Thus, vitamin A deficiencies can cause ill health effects, but so can vitamin A when taken in excess. As with anything you put into your body, pay attention to the RDA and take care not to deviate too much from that amount.
Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.