Vitamin A is a fat-soluble vitamin that comes from two sources: preformed retinoids and provitamin A carotenoids. That may sound rather complex, but put in simpler terms, retinoids are found in animal sources such as eggs, dairy products such as whole milk, and liver. Vitamin A found in animal foods like these is called preformed vitamin A and is absorbed in the form of retinol, one of the most usable forms of vitamin A.
Provitamin A carotenoids, on the other hand, are found in plant foods like colorful fruits and vegetables including yellow vegetables and carrots. Many fruits and vegetables, however, contain beta-carotene and other vitamin A precursors, which the body can turn into vitamin A—and this is an effective way of getting vitamin A for many.
In fact, according to the Office of Dietary Supplements fact sheet on vitamin A, in the United States, approximately 26% of vitamin A consumed by men and 34% of vitamin A consumed by women is in the form of provitamin A carotenoids. They note that the common provitamin A carotenoids found in foods that come from plants are beta-carotene, alpha-carotene, and beta-cryptoxanthin—with beta-carotene leading the pack in most efficiently making retinol.
But what’s so special about vitamin A? Lots.
You may have heard about how vitamin A helps with eye health, but vitamin A does much more than help you see in the dark. (Note: Vitamin A is essential for the formation of something called visual purple, a pigment found in the retina of the eyes and is needed for night vision.) Vitamin A also stimulates the production and activity of white blood cells and takes part in the remodeling of bone.
Additionally, vitamin A is necessary for the health of the outer skin as well as the mucous membranes that line the respiratory, gastrointestinal, and urinary tracts. Add that to how vitamin A serves to support cell growth and division as well as its importance in immune health, and you have a pretty important vitamin.
What’s more is that approximately 90 percent of the body’s vitamin A is stored in the liver with small amounts deposited in the fatty tissues, lungs, kidneys, and retinas. Under stressful conditions, however, the body uses this reserve supply when it doesn’t receive enough of the vitamin from the diet. Interestingly enough, the liver also needs a sufficient supply of zinc so that it can mobilize and release stored vitamin A into the bloodstream so it is also important to get enough zinc in your diet.
Vitamin A deficiency can cause night blindness and actual blindness if the deficiency causes dryness of the cornea, resulting in corneal and retinal damage. A deficiency in vitamin A can also diminish the body’s ability to fight infections.
There is a growing interest, however, in early forms of vitamin deficiency that do not display obvious symptoms—as this early form of vitamin A deficiency may increase children’s risk of developing respiratory and diarrheal infections, decrease their growth rate, slow their bone development, and decrease their chances of surviving a serious illness. Children at risk include toddlers and preschoolers, the poor, the undernourished, and kids with inadequate fat digestion or absorption as well as those with diseases of the pancreas, liver, or intestines.
You see? Vitamin A is not just for the eyes.