Since we've been looking at eye exercises, it seems fitting to focus on the vitamin that feeds and helps maintain them in good health. Vitamin A is not alone but is part of a family which includes beta-carotene. However, today we'll look at retinol which is the specific name for vitamin A.

Retinol is the form of vitamin A the body recognizes as immediately available for use. In fact, before betacarotene can be used, it must undergo a process of change in the body which takes several hours until it turns into retinol.

Vitamin A has a long list of ways in which it's generally helpful to body cells, but let's look mainly at its value to your eyes. Recent researchers are convinced that one of the best ways to prevent cataracts is to eat more fruits and vegetables that are high in beta-carotene.

Paul F. Jacques, D. Sc., was an epidemiologist with the U.S. Department of Agriculture's Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts. He was quoted in Prevention's Food & Nutrition, a 1993 book release as saying, "Eating a healthy diet may delay the usual aging of the lens of the eye and so delay cataracts." (p. 6).

Here is why vitamin A is so important to your vision. The retina is a small postage stamp-sized area in the back of your eye. It's filled with tiny cells known as rods and cones. Cones enable us to see color, while rods determine shades of gray that enable us to see in varying degrees of the dark.

There's a pigment in the retina called rhodopsin or visual purple. Rhodopsin is formed by the protein opsin connecting to vitamin A. The connection puts a bend to the vitamin A molecule which snaps back to its straightened form as it's used up in the visual process.

Rhodopsin is found only in rods. In cones, vitamin A connects with three different opsins forming three pigments giving us our three primary colors: red, green, and blue. The brain then mixes the colors to give us our extraordinary visual palette of shades and hues.

Visual purple is constantly being formed, used up, and reformed. Vitamin A is responsible for the electrical transmission of light into the visual images seen by the brain. Vitamin A is also important to the health of the cornea, the transparent covering over the pupil and iris.

What happens if you're short of vitamin A? Perhaps the first noticeable thing is that when driving at night, oncoming headlights may cause visual pain and an immediate diminishing of sight which is slow to recover. However, for an office worker who sits under the glare of fluorescent lights or works with computers, their first symptom might be burning, stinging eyes or aching or eye pain. Glare from paper reflected into the eyes increases the constant need for vitamin A.

People who experience unusual light sensitivity to where they are most comfortable wearing sunglasses may be short on vitamin A. Bright light can cause pain to these individuals.

I remember reading about an explorer who developed such intense eye pain that he could not function. An Indian fed him the liver of fish and shortly his pain diminished.

Some have been quick to dismiss such folklore, but we now know that fish liver is one of the most concentrated sources of vitamin A in the retinol form.

Other symptoms of vitamin A shortage include recurring styes, itching, inflamed eyelids, headache, and even nervousness.

Animal sources of vitamin A are liver, kidney, sweetbreads (term for pancreas), eggs, and butterfat.

Some physicians still recommend margarine over butter. However, as you'll see later, the process of manufacture that margarine undergoes makes it, in the opinion of some, unfit for human consumption. Butter must be consumed with extreme moderation, but because it's a natural food, it's used within the body in a beneficial way which can't be said about margarine.

Eggs are another source of contention. People are concerned about the cholesterol content of the yolks. The yolks also contain lecithin, a natural agent that enables your body to use the cholesterol in a manner that does not cause your blood levels to elevate.

I read once about a physician who sent his patients on vacation and told them to eat eggs. He took their blood cholesterol before their trip, and afterward. He found no elevation in any case; and in some, there was a decided lowering of cholesterol.

If your physician told you to avoid butter and eggs, I'm not telling you to go against the recommendation. However, it would be a good idea to read up on these matters so you might be better informed and then discuss the issues with him or her.

Sources of beta-carotene include Swiss chard, kale, spinach and other green leafy vegetables, broccoli, green beans, carrots, yams, sweet potatoes, yellow or acorn squash, apricots, and all brightly colored fruits, tomatoes, lettuce, and asparagus. The general rule of thumb is the brighter or more intense the color the greater the beta-carotene concentration.

In order for either vitamin A or beta-carotene to be absorbed, they must first combine with bile salts in the small intestine. If the diet is extremely low in fats, not enough bile salts will be produced and these vitamins may pass through the body in waste matter.

Another important factor is vitamin E consumption at the same time vitamin A and or beta-carotene are eaten. A lack of vitamin E will cause vitamin A or retinol to be oxidized meaning it's destroyed before it can be used.

If the B complex family member choline is not present in the diet, retinol cannot be stored within the liver for future use.

Based on all of these variables and the modern American tendency to eat junk food, it's little wonder people are showing up with symptoms of their eyes, a weakened immune system, and a variety of skin conditions as well.

Some medical personnel react to their patients taking vitamin A supplements. In medical training people sometimes heard horror stories about people who took too much vitamin A and had terrible things happen such as: liver enlargement (due to vitamin A storage there), hair loss, lack of appetite, weight loss, dryness and cracking of lips, loss of sleep, headaches, joint and bone pain.

There is the celebrated story of the woman who consumed close to a bushel of carrots every day by becoming juicer happy. Her skin turned a lovely shade of yellow-orange. It's rare to find someone so dedicated to carrots. However, if that happens, stopping the intake will cause the coloration to fade away.

Synthetic vitamin A is usually coupled with vitamin D and there's reason for caution about consumption of artificial vitamins. Pregnant women should be especially careful as an overdose can cause problems with their developing baby.

Under normal conditions, the liver can handle about 500,000 I.U. (International Units) according to Dr. Thomas Moore of Cambridge, England's Dunn Nutritional Laboratory. (1967). However, most normal people would not consume that amount in a month.

Normal toxic doses are usually given at 50,000 I.U.a day. However, few people would take more than the 5,000 I.U. which the U.S. Food and Drug Administration set in 1973 as the RDA or Recommended Daily Allowance.

Many authorities believe that should be reevaluated to 10,000 I.U. with children over four taking half that amount.

I have not heard of the above list of symptoms from vitamin A overdose from any natural source. Most people do not get enough of this vitamin to cause problems. As we've seen from types of factors that must accompany vitamin A consumption, we're looking at rarities that would under normal conditions not appear.

Perhaps the best supplement of retinol is cod liver oil. (No gagging allowed.) It now comes in flavors such as orange, lemon, and mint. At no time have I ever read or heard of a problem in taking cod liver oil as a source of vitamin A (and D) especially when consumed in a modest manner.

It's important when taking supplements to check the total amounts being consumed, especially if one is taking more than one type of tablet or source.

I'm not trying to persuade you to take supplements. I encourage you to read helpful resources, consult your physician, and together decide about how you want to care for your health.

Bibliography
Guyton, Arthur C., M.D., Textbook of Medical Physiology, 7th Edition. Philadelphia: W.B. Saunders Company, 1986.
Haas, Elson M., M.D., Staying Healthy with Nutrition. Berkely: Celestial Arts, 1992.
Prevention Staff, The Complete Book of Vitamins, Emmaus: Rodale Press, 1972.
The Human Body Series, The Eye, Window to the World. New York: Torstar Books, 1984.

Suggested Resources:
Balch, James F., M.D., and Phyllis A., C.N.C., Prescription for Nutritional Healing. Garden City Park, NY: Avery Publishing Group, Inc., 1990.
Dunne, Lavon J., Nutrition Almanac, Third Edition . New York: McGrawHill, 1990.
Quillin, Patrick, Ph. D., R.D.,Healing Nutrients,, New York: Vantage Books, 1989.