Vitamin A is commonly known as the vitamin needed for good eyesight. Along with promoting vision, vitamin A is also vital for regulating genes, maintaining healthy skin, supporting the immune system and producing red blood cells. Deficiencies are rare in first world countries and are largely a problem of developing countries. A vitamin A deficiency primarily causes impaired vision and increases susceptibility to infectious diseases.
There are several forms of Vitamin A that are needed by the body. These include:
- Retinal - a metabolite of vitamin A required for vision.
- Rentinol - the form of vitamin A that can be stored by the body and converted to retinal when needed.
- Retinioc acid - a growth factor needed primarily to regulate genes.
Vitamin A Is important for vision
When we look at objects, light is reflected from the object and enters the eye, striking a tissue located in the back of the eye. This tissue is known as the retina. When light strikes the retina, retinol is converted to retinal, which is then shuttled to rods - the cells that help you to see in the dark. In rod cells, retinal binds to a protein called opsin. As a result, opsin changes shape and causes nerve impulses to be generated. These nerve impulses then carry messages to the brain regarding the objects in our visual field. Retinal is then converted back to retinol, ending the visual cycle.
A hallmark of vitamin A deficiency is night blindness - an impaired ability to see in low light conditions. This is because with a reduced availability of retinol, the nerve impulses necessary for our brain to interpret visual information are hindered.
Vitamin A Regulates Genes
Our genes hold the code for vital proteins needed to carry out the body's day to day functions. Thus, when these proteins are needed, the genetic code needs to be transcribed. However, gene transcription is highly regulated. This includes when it occurs and how fast it occurs. The retinoic acid form of Vitamin A helps to regulate the rate of gene transcription.
Vitamin A Supports the Immune System
The skin and the lining that covers the digestive, respiratory and urinary tracts are important components of the immune system. They are your body's first barrier against infection. The retinol form of vitamin A is responsible for maintaining the function of the cells that make up these barriers. Vitamin A is also needed for the formation and activation of white blood cells.
Vitamin A Is Important for Red Blood Cell Production
All blood cells are developed from stem cells. Vitamin A facilitates the specialization of stems into red blood cells. Vitamin A also allows iron to be incorporated into hemoglobin - the oxygen carrying component of red blood cells.
Sources of Vitamin A
Vitamin A can be sourced from both plants and animals. A few of the best sources of vitamin A include:
- Cod liver oil
- Whole milk
- Sweet Potato
- Squash/ butternut