By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital
Edited by Kate Findley and proofread by Angela Shoemaker, Wondrium Daily
You might be familiar with vitamin A’s benefits when it comes to vision. However, according to Professor Anding, vitamin A is a great multitasker and plays many important roles in the body.
Vitamin A Benefits
Vitamin A is an important fat-soluble vitamin and as such, much more likely to be toxic. Still, vitamin A carries a wide variety of benefits and is particularly important for normal and healthy vision.
Vitamin A is a necessary constituent to the visual pigment rhodopsin, which is found in the rods. These are necessary to see black and white, as well as for you to see during the night. It also plays a key role in gene transcription and making DNA and RNA; these are necessary steps for ultimately synthesizing proteins that we need.
Vitamin A is also a conductor in that it teaches cells what they should become. This is known as cell differentiation, which is important in clinical nutrition because cells need to know which direction to go in. Epithelial cells, which are cells that come from the surface of your body such as skin or blood vessels, normally produce mucus that lubricates and prevents keratinization, the thickening of skin.
Immune Function and Vitamin A
Vitamin A is also needed for T lymphocytes, which are central to the immune system. Thus, when it comes to immune function, vitamin A protects the immune system via its role in epithelial cell development. These skin cells line the intestinal tract.
If they become keratinized, and thicken and crack, bacteria can be allowed to translocate. Since a lot of bacteria is normally present in the food that we eat—including bacteria transferred from our hands—our bodies are protected from bacterial invasion if the intestinal cells are doing their job. If those cells are differentiated, they don’t become keratinized. When the skin cells don’t crack, the bacteria won’t be able to translocate from the gut into the blood, which would make you ill.
Other important roles of vitamin A include normal embryonic development and reproduction, bone metabolism, and the growth and development of bones. Additionally, vitamin A is needed for hematopoiesis, the formation of blood components.
Sources of Vitamin A
Fruits and vegetables are the best sources of vitamin A. Fresh-cooked carrots have about 671 micrograms of vitamin A for a 4-ounce serving. Six ounces of carrot juice has over 1,600 micrograms.
A medium sweet potato baked with the peel has over 1,000 micrograms. A fourth of a medium cantaloupe, which would be raw, has 230 micrograms. When you take it as a supplement, you’re going to often get above and beyond those amounts.
You may be wondering how much vitamin A you actually need. The recommended daily allowance (RDA) in micrograms per day for males, ages 19 to 70, is 900 micrograms. Females, ages 19 to 70, need about 700 micrograms. Both amounts are very easily met within a normal diet.
Too Much of a Good Thing
Important to remember, vitamin A is a fat-soluble vitamin, which means that it can be toxic when taken in excess. Although beta-carotene is much less likely to be toxic than preformed vitamin A, too much beta-carotene can actually cause yellow-orange skin.
“I had a client one time that absolutely loved carrots and felt that he needed to have adequate amounts of carrots every day,” Professor Anding said. “He ate bags of carrots. You could look at the palms of his hands and the soles of his feet, and they actually had a nice orange glow to them.”
Additionally, impotence and other sexual dysfunction can occur with a level of vitamin A that’s outside of the therapeutic range. There can be calcium loss in bones that can lead to osteoporosis and vague symptoms of irritability, nausea, headache, fatigue, dizziness, and diarrhea. Skin and hair changes—skin peeling, itching, oily skin, hair loss, cracks at the corners of the mouth. In infants, an abnormal softening of the skull bone and poor weight gain can also result.
Sun-tanning pills, in their early days, had high-dose beta-carotene in them. They, too, would turn your skin yellow-orange. However, for the average person who is not taking vitamin A supplements or going overboard with carrots, it should be easy to stay within a healthy range.
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.
