Vitamin A: The First Recognized Vitamin

Vitamin A, in the forms retinol, retinal, and retinoic acid, was the first vitamin recognized as such by early researchers. Beta-carotene, the stuff that makes carrots and yams orange, is often mistaken for vitamin A as well; in actuality, it is a precursor, a substance that once in the body can easily be transformed into vitamin A.

No vegetable provides vitamin A; instead, they provide carotenoids, various substances that have vitamin A type activity or that sometimes can be changed into vitamin A (like beta-carotene). True vitamin A is derived only from animals, mostly in the form of retinoids.

Regardless of its source, you must have vitamin A in order to carry on several vital life functions.

What Vitamin A Does

Vitamin A is best known for promoting good vision. What many don't realize is that it also helps maintain healthy skin and is critical for proper reproduction and growth.

Its effects on the skin has led to vitamin A derivatives being used in many oral and topical applications, primarily as Retin-A, designed to eliminate wrinkles. Retin-A is a form of retinoic acid, and it acts like a hormone in your body to regulate cell differentiation. Another derivative, Accutane, is commonly used to combat cystic acne, and is very effective. However, this only works with the derivative. Large doses of straight vitamin A won't have any effect on acne, and is much more likely to harm your body.

Interestingly, you can't take retinoic acid alone as vitamin A; your eyes need retinal, a different form of vitamin A. Retinal is critical for any vision, not just good vision. It is used in visual processes to help transmit light energy through the back retina of the eye to the optic nerve. Most retinal is preserved by the body; however, in the normal use of your eyes, small amounts of retinal are lost necessitating that the body replace it. Without a steady small flow of retinal, you
will go blind.

The third form of vitamin A, retinol, supports reproductive cell production and good fetal development. Too much vitamin A in any form, however, can cause birth defects in babies.

Vitamin A Deficiencies

The first sign of a deficiency in vitamin A is night blindness; if you normally see well at dusk and night and then one day you can't, consider upping your dose of vitamin A. This deficiency shows up fairly often in pregnant women; the baby's development pulls vitamin A away from the mother's body, resulting in small deficiencies in the eyes and sometimes the skin.

A lack of vitamin A can lead to extreme susceptibility to measles, making normal childhood illness deadly. It can also lead to the keratinization of the skin, a condition in which rough scaly patches that feel a little like fingernails develop.

Fortunately, in adults it usually takes one to two years for enough vitamin A to be depleted from the body to cause negative effects. In children, however, depletion happens much more quickly.

Vitamin A Toxicity

Beta-carotene overdoses are easy to spot: your skin turns to a characteristic yellow-orange shade, caused by the storage of beta-carotene in the layer of fat just under the skin. If this is caused by eating too many carrots, it's not harmful at all. If, in contrast, it's caused by taking too many supplements, it can cause the destruction of vitamin A in the body and encourage too much cell division, which can lead to skin cancer.

Pregnant women taking doses of vitamin A only four times the RDA have a one in 57 chance of giving birth to a malformed infant. It is especially important for them to take vitamins in moderation.

The Least You Should Know

Fat-soluble, so supplements should be taken with a meal or a glass of milk.
Adult RDA: 700-900 micrograms/day
Max recommended dose: 3000 micrograms/day (a level that can cause birth defects in fetuses)
An adult can carry as much as two years worth of vitamin A stored in the liver.