Joseph R. Anticaglia MD
Medical Advisory Board
Janet told this story: “When I was 4 or 5 years old, I remember my mother saying, ‘Eat the carrots. They’re good for your eyesight.’”
Janet continued, “While in the first grade, I had difficulty reading. During a school conference, the teacher advised my parents to have my eyes examined. When the doctor told my mother that I needed eyeglasses, she wept.”
Mother: “Did I do something wrong?”
Her doctor said, “Of course, not. Sometimes we just don’t know why things like this happen. But every year we continue to learn new things about vision and vitamin A. We’ve discovered it’s not only important for eyesight.”
Functions of Vitamin A
Many are aware that vitamin A is needed for normal eyesight, especially in low light. Vitamin A helps maintain a healthy cornea, the clear, outer layer of the eye. It’s also needed by the retina, the nerve layer that lines the back of the eye, for it to function normally.
Less familiar is the indispensible role it plays in remodeling bone to promote growth in children. It has an immune, anti-infective function since the body depends on an adequate supply of vitamin A to defend itself against infections.
Vitamin A is needed for reproduction, for healthy skin and for the protective internal linings of the body such as found in the intestines, lungs and vagina. It assists in cell differentiation wherein each cell develops to perform a specific job. The goblet cells secrete mucus which helps protect the internal linings of the body.
Vitamin A is part of a group of fat-soluble vitamins (A. D. E and K) found in the fats and oils of foods. It’s stored in the liver and the body’s fatty tissues.
There are two basic forms of Vitamin A:
- Retinol — Animal based foods
- Beta-carotene — plant based foods
Beta-carotene is an antioxidant and an important component in plant foods for vitamin A. It’s called “provitamin A” because it needs to be converted in the liver to the active form retinol. Some examples of plant foods containing carotenes (carotenoids) are carrots, sweet potatoes and spinach. Fortified cereals and milk are also a source of vitamin A.
Retinol is the active form of vitamin A. Good sources of this vitamin are found in cod liver oil and liver. Other sources are butter, eggs and cheese. It’s called “preformed” vitamin A because
retinol is already present in certain seafood and animal foods. Vitamin A is also known as retinol because of its association with the pigments of the retina.
Deficiency of vitamin A occurs when the diet is consistently low in retinol and beta-carotene. At times, e.g. due to sickness, the body is incapable of converting plant foods with beta-carotene to vitamin A. In developing countries, vitamin A deficiency is an important cause of blindness and problems with the immune system.
The World Health Organization estimates that in developing countries 190 hundred million children and 19.1 million pregnant women are more susceptible to infections because of an impaired immune system due to a lack of vitamin A.
In the United States, several factors can contribute to low levels of vitamin A, particularly in the elderly and poor.
- Malabsorption syndromes secondary to surgery for obesity or medical conditions.
- Premature infants are at risk to develop vitamin A deficiency because they do not have adequate liver stores of vitamin A at birth.
- Persons with Cystic Fibrosis have pancreatic insufficiency putting them at an increased risk for vitamin A deficiency because they have difficulty absorbing fats.
- Mineral oil laxative abuse.
- Not consuming enough food with preformed vitamin A or beta-carotene…
- Conditions which prevent the conversion of beta-carotenes to active vitamin A.
- Insufficient bile. Bile is the fluid that’s secreted by the liver and stored in the gallbladder. Vitamin A requires bile for it to be absorbed by the body.
If you lack vitamin A you are at an increased risk to experience night blindness, dry eyes and irreversible corneal damage. You may be more susceptible to dry, scaly skin, an increase incidence of infections and children might experience developmental problems. Vitamin A deficiency places children at a greater risk to develop severe cases of measles.
Vitamin A Toxicity
Too much beta-carotenes can turn the skin to a yellow-orange color most noticeably on the palm of the hands and soles of the feet The whites of the eyes remain white and the excessive intake of beta-carotenes is otherwise benign.
Too much preformed vitamin A from food or supplements can cause a variety of problems that range from headache to coma to even death. Pregnant women should not take high doses of vitamin A supplements because they can cause birth defects.
Vitamin A is essential for the healthy growth and maintenance of our body. Although vitamin A deficiency is rare in industrialized countries, the lack of vitamin A is a pervasive world-wide affliction affecting millions of people.
- S. Pinkaew et al; Triple fortified rice containing vitamin A reduced marginal vitamin A deficiency in school aged Thai children; Journal of Nutrition, Feb 5, 2014
- WHO. Global prevalence of vitamin A deficiency in populations at risk 1995–2005. WHO Global Database on Vitamin A Deficiency. Geneva, Switzerland: World Health Organization; 2009.
- NIH; Vitamin A; October 5, 2018
- Rothman, K et al; Teratogenicity of high vitamin A intake; N Engl J Med; Nov 23, 1995
- Anticaglia, Joseph R; Vitamin Basics; HC Smart, 2019
This article is intended solely as a learning experience. Please consult your physician for diagnostic and treatment options.