While vitamin A can't turn bad eyesight into perfect vision, this important nutrient can help prevent a wide range of eye conditions when consumed in sufficient quantities. Understanding the many different types of vitamin A and learning about the other food compounds that the body can convert into vitamin A can help make the exact relationship between vitamin A consumption and vision much clearer.
Vitamin A actually refers to a group of compounds, including retinol, retinal and retinoic acid, which are collectively known as preformed vitamin A; retinol and retinal can be found in food. Some dietary sources of vitamin A include sweet potato, spinach, carrots, pumpkin, cantaloupe, peppers, mangoes, apricots, broccoli and eggs. The Recommended Daily Allowance for vitamin A is 700 micrograms per day for women and 900 micrograms a day for men.
Provitamin A Carotenoids
Another group of compounds related to vitamin A are the provitamin A carotenoids, plant compounds that can be converted by the body into vitamin A. These include beta-carotene, alpha-carotene and beta-cryptoxanthin. Once these provitamin A carotenoids are converted into vitamin A in the body, they act exactly the same as pre-formed vitamin A, which is the active form. It takes 12 micrograms of dietary beta-carotene to equal the activity of 1 microgram of retinol and 24 grams of other carotenoids to equal the same level of activity.
Vitamin A in Eyes
Vitamin A in the form of retinol collects in the surface cells of the retina of the eye. The retina is the portion of the eye that senses light and transmits the information about what it sees along nerves to the brain. When needed, the cells of the eye can take stored retinol and use it as a building block for rhodopsin, a compound necessary for night vision.
Deficiencies and Vision
Mild deficiencies in vitamin A can cause night blindness. As a deficiency progresses, the individual might develop a type of eye dryness that damages the cornea, the clear covering that protects the eye. In severe cases, ulcers and scarring develop on the cornea, and the person might go blind. Getting sufficient vitamin A or provitamin A carotenoids in the diet helps prevent corneal damage.
The progressive eye disease macular degeneration usually strikes in old age and can lead to total blindness if left unchecked. The Age-Related Eye Disease Study, or AREDS, which was sponsored by the National Eye Institute, looked at the effect of vitamin A along with vitamins C and E, zinc and copper when used together as a supplement to fight macular degeneration. In the study, researchers found that individuals with mild to intermediate macular degeneration who took the supplement were 25 percent less likely to develop advanced macular degeneration.
- eyes image by Mat Hayward from Fotolia.com
This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.