Since our eyes are such a valued part of our everyday life, let's focus on the vitamin that feeds and helps maintain them in good health. Vitamin A is part of a family which includes betacarotene. Here we'll explore 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 helps all body cells, but we'lll look mainly at its value to your eyes. Researchers have been convinced that one of the best ways to prevent cataracts is to eat more fruits and vegetables which are high in betacarotene.
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 and 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).
So, why is vitamin A so important to your vision? The retina is a small postage stamp sized area in the back of your eye. It' is filled with tiny cells known as rods and cones. Cones enable you to see color, while rods determine shades of gray that enable you to see in varying degrees of darkness.
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 in the vitamin A molecule which will 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 which give 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 which is the transparent covering over the pupil and iris.
What happens if you're short of vitamin A? One of the first things is that when driving at night, oncoming headlights may cause visual pain and an immediate dimming of sight which slowly to recovers. 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 eye pain or aching. Glare from paper reflected into the eyes increases the constant need for vitamin A.
People who experience unusual light sensitivity to the point that they're most comfortable wearing sunglasses may be short on vitamin A. Bright light can actually cause pain to these individuals.
I recall reading of an early explorer who developed such intense eye pain that he could not function. An Indian fed him the liver of a fish and soon his pain diminished. Most of us would recoil at that thought, but it saved that man's eyes. Some are quick to dismiss such folklore, but we now know that fish liver is one of the most concentrated sources of vitamin A in its retinol form.
Other symptoms of vitamin A shortage include: recurring styes, itching, inflamed eyelids, headaches and even nervousness.
Animal sources of vitamin A are: liver, kidney, sweetbreads (the common term for the pancreas), eggs and butterfat.
Although margarine is still being sold, more people are turning to butter as they can afford it. They're learning that the process of manufacturing margarine makes it, in the opinion of some, unfit for human consumption. Butter must be consumed with moderation, but because it's a natural food, it's used in the body in a beneficial way which cannot be said about margarine.
Eggs are another source of contention. People have been taught to be concerned about the cholesterol content of egg yolks. However, the yolks also contain lecithin which is a natural agent that enables your body to use that cholesterol in a way that does not cause blood levels to elevate.
I once read of a physician who sent his patients on vacation and told them to eat eggs. He took their blood cholesterol before their trip, and afterwards. 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, Im not saying to go against those recommendations. Rather, it would be a good idea to read up on these matters so you might be better informed and then discuss the issues with them.
Sources of betacarotene 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 that the brighter or more intense the hue of green, yellow or orange, the greater the betacarotene concentration.
In order for either vitamin A or betacarotene 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 simply pass through the body in waste matter.
Another factor is the importance of vitamin E consumption at the same time vitamin A and betacarotene are eaten. A lack of vitamin E will cause vitamin A or retinol to be oxidized which means it's destroyed before it can be used.
If the B complex family member choline is not present in the diet, retinol can't be stored in 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 having symptoms not only in their eyes, but also experiencing a weakened immune system and a variety of skin conditions as well.
Some medical personnel overreact to the idea of patients taking vitamin A supplements. One reason for this is in medical training people may hear horror stories about people who took too much vitamin A and had terrible things happen such as: liver enlargement (due to the storage of vitamin A there), hair loss, lack of appetite, weight loss, dryness and cracking of lips, loss of sleep, headaches, joint and bone pain.
There is also the story of a woman who consumed nearly a bushel of carrots each day by daily drinking a lot of carrot juice. Her skin turned a lovely shade of yellow-orange. It's rare to find someone so dedicated to carrots. However, if that were to happen, simply stopping the intake will cause the color to fade away.
Synthetic vitamin A is usually coupled with vitamin D and there is reason for caution about consuming artificial vitamins. Pregnant women should be especially careful as an overdose can cause problems with her 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. that 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've not heard of the above list of symptoms being caused by a vitamin A overdose from any natural source. Most people do not get enough of this vitamin to cause problems.
Perhaps the best supplement of retinol is cod liver oil. (No gagging, please.) It now comes in flavors as orange and lemon. We're not fanatic about taking it, but each of us may take a tablespoonful from one to three or four times a week. 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 such a modest manner.
Many brands also come in capsule form.The following site recommended Vital Omega 3 by Vital Nutritive.
It's important when taking supplements to check the total amounts being consumed, especially if one is taking more than one type of source.
I'm not trying to persuade you to take supplements. My purpose is to give you a look at some possibilities that can possibly free you from certain groups of symptoms. Consult your physician and together decide the choices you want to make for your health.
References:
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.
PS. This is an edited version of a health column I wrote in 1993. Consider doing your own research. There is more current information, but this is a good basic start. Here's to healthy eyes!
Nancy L. Pidutti, PhD, NHH, Author, Hospital Chaplain
