(NaturalNews) Vitamin A is an essential nutrient which plays numerous important roles in the human body, most notably in eye health, proper growth and immune function.

This vitamin was discovered sometime in 1913 by two groups of researchers, who found that young animals which consumed a diet lacking in natural fats suffered from inhibited growth and poor immunity. Their eyes also became badly infected and inflamed. However, the addition of either butterfat or cod-liver oil to their diets - both high in vitamin A - quickly reversed their conditions.

Vitamin A was the first fat-soluble vitamin to be recognized and it is sometimes referred to as the "anti-infective vitamin".

Key functions

This vitamin plays a part in proper growth and development. Some of the body functions which are influenced by vitamin A include: manufacturing and activity of adrenal and thyroid hormones; maintaining nerve cell structure and proper function; immune function; cell growth; plus maintaining skin structure and health. Research suggests vitamin A helps with many skin ailments, including acne and psoriasis.

Vitamin A has profound effects on the eyes and visual system as well. There are four types of vitamin A-containing compounds in the retina of the human eye which play a role in vision. When a person is deficient in vitamin A, night blindness or reduced adaptation of the eyes to darkness is an early tell-tale sign.

Deficiency

A deficiency in vitamin A can result from inadequate intake in one's diet or due to some secondary reason which inhibits the absorption, storage or transport of the vitamin. Exposure to toxic chemicals could also elevate vitamin A degradation in the liver, thus leading to an increased need for the vitamin. Vitamin A deficiency is widespread in developing countries, particularly Asian countries.

Some effects of vitamin A deficiency are:

• Higher mortality rates - even slight vitamin A deficiency is linked to a marked increase in mortality.

• Poor growth and development.

• Suppressed immune function characterized, for example, by reduced ability to launch an effective antibody response and lowered levels of helper T-cells. This makes a person more prone to infectious diseases, including chicken pox, respiratory syncytial virus (RSV), measles, pneumonia, sinusitis, AIDS, colds and other respiratory infections. Worse, during the course of an infectious disease, the body's stores of vitamin A are depleted, contributing to a vicious cycle which further increases one's infection rate.

• Vision issues like night blindness and dry eyes (cornea and conjunctiva). In severe cases, an eye disease known as xerophthalmia could result, a condition which afflicts millions of Asian children annually.

• Dry hair

• Dry skin and skin disorders like acne.

• Compromised mucous membranes in the respiratory, gastrointestinal and genitourinary tracts.

• Ear abscesses

• Insomnia

• Fatigue

• Reproductive issues

• Weight loss

Food sources

Dietary sources of vitamin A fall into two categories - foods which contain preformed vitamin A and foods which contain provitamin A, compounds that are converted to vitamin A in the body. The body's ability to properly absorb vitamin A is dependent on healthy mucosal cells plus the presence of bile, pancreatic enzymes, fat, protein and antioxidants. Conversion of provitamin A to vitamin A depends on the presence of protein, zinc, vitamin C and thyroid hormones.

The richest sources of preformed vitamin A include liver, kidney, butter and whole milk.

Good sources of provitamin A are dark green leafy vegetables like kale, spinach and collards; yellow-orange vegetables like carrots, yams, squash, and sweet potatoes; plus other foods like apricots, green peppers and dandelion root.

More details on foods high in vitamin A and provitamin A is available here.

Sources for this article include:

Murray, Michael, ND., Pizzorno, Joseph, ND., and Pizzorno, Lara, MA, LMT. The Encyclopedia of Healing Foods. New York, NY: Atria Books, 2005. Print.

Stengler, Mark, ND. The Natural Physician's Healing Therapies: Proven Remedies Medical Doctors Don't Know. New York, NY: Prentice Hall Press, 2010. Print.

Murray, Michael T., ND. Encyclopedia of Nutritional Supplements: The Essential Guide for Improving Your Health Naturally. New York, NY: Three Rivers Press, 1996. Print.

Balch, Phyllis A., CNC. Prescription for Nutritional Healing: A Practical A-to-Z Reference to Drug-Free Remedies Using Vitamins, Minerals, Herbs & Food Supplements. 5th ed. New York, NY: Avery, 2010. Print.

About the author:
Reuben Chow has a keen interest in natural health and healing as well as personal growth.

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