Vitamin A is an all-important nutrient on which many chemical processes in the body depend. Without adequate levels of Vitamin A, proteins, minerals and water-soluble vitamins cannot be utilized by the body.
This powerful vitamin also acts as an antioxidant, protecting the body against pollutants and free radicals. It provides a vital role in building strong bones and healthy blood; it stimulates the gastric juices that are needed for digestion; and is needed for good night vision and color perception.
Another of its key functions is the protection of mucous membranes- the linings of the mouth, nose, throat and lungs; without this vitamin, these tissues dry out and cannot perform their vital functions.
There are two kinds of Vitamin A. Vitamin A in food can come from retinol, which is also called preformed Vitamin A, or from a group of components called carotenoids, also known as provitamin A.
Vitamin A is fat-soluble, so the main sources are foods that contain some fats and oils. Studies have also found that the body cannot convert carotenes into Vitamin A without the presence of fat in the diet. Therefore, it's essential to include fats and oils along with food sources in the diet to make sure the body gets enough of this nutrient and is able to absorb it.
Sources of preformed Vitamin A, or retinol,are from foods that come from animals, including butterfat, egg yolks, organ meats, seafood and fish liver oils.
Provitamin A, or carotene, is also a powerful antioxidant. It is found in all yellow, orange, red or dark green fruits and vegetables.
The body stores surplus amounts of Vitamin A in fatty tissues like the liver, so excessive doses can be toxic. Therefore it is best to obtain most Vitamin A intake from natural sources, and not from synthetic supplements.