While we were living in Mexico, an ophthalmologist friend (Dr. Mario Turati) asked me to tell him why vitamin A was so important to the eyes when he was convinced that the eyes do not contain that nutrient. Ever since then, I have been intrigued with how much diet plays in good vision. It was this same friend who related this story to me.
One of his patients came in for an eye exam complaining of poor vision in one eye. Since his livelihood was driving a taxi, it was important for him to have this corrected. The eye was examined and the problem found. When the doctor started to examine the other eye, the man said, “Oh, don’t bother with that one, I can’t see a thing out of it”. Sad part was, he was not the only such taxi driver like that. I rode with several of them!
Diet and good vision involves more than just “eating carrots” – although it was good advice from our mothers. The following will give you a rough idea of just some of the nutrients that the eye requires in order to do its job effectively. Since vitamin A is the most well-known and studied nutrient involving vision, we will begin with that one.
Vitamin A, or retinol, is an element most closely tied to vision. The retina contains two kinds of light sensitive receptors, rods and cones, which receive light and provide information about the object we are seeing. This information is converted by the retina to electrical impulses and sent to the brain, which translates these impulses into an image.
The rods are responsible for peripheral vision and function in dim light. They contain the pigment rhodopsin, or visual purple, which is chemically very similar to vitamin A. The cones are responsible for central vision, detail, and colour. They require bright light to function. The cones produce iodopsin, or visual violet.
In both these pigments, vitamin A, in the form of retinaldehyde, is the prosthetic group; but the proteins to which the aldehyde is attached are different. When light strikes rhodopsin, changes occur in the chemical configuration of retinaldehyde; and the pigment splits into its component parts, retinaldehyde and protein.
These changes initiate a nerve impulse that is then transmitted to the brain by way of the optic nerve. Regeneration of rhodopsin occurs in the dark, but some retinaldehyde is lost in each cycle so that a constant supply from the blood must be present.
When light strikes a rod, the rhodopsin is broken down and used up. In order to make new rhodopsin and continue to function, the rod must draw on vitamin A within the body. Without the replenishment of vitamin A, the rods will eventually be destroyed and vision will diminish.
The first sign of vitamin A deficiency is night blindness. In dim light, the eye depends on the rods to maintain vision. Thus, when there is not enough vitamin A, the rods cannot function properly and night blindness occurs.
Vitamin A is also essential for maintaining mucous membranes that line the tear ducts, glands, and other places in the eye. Mucous secretions maintain the integrity of the epithelium, especially the membranes lining the eyes, and provide resistance to bacterial invasions.
Therefore, tissues weakened by the lack of vitamin A are more susceptible to infections. A study, caried out at the Massachusetts Eye and Ear Infirmary, in Boston, showed that applying vitamin A directly to the eye may stimulate mucous-producing cells.
Vitamin A deficiency is the cause of xerophthalmia, which is a leading cause of blindness in developing countries, particularly Africa and Latin America. According to Helen Keller International, xerophthalmia impairs the vision of up to ten million children annually.
Xeropthalmia responds well to nutritional supplements of vitamin A (especifically for dry eyes), vitamin B6, C, and zinc, which all work together to help heal the problem. However, third world children do not have access to nutritious diets, never mind these vital nutrients.
Harvard researchers have proven that vitamin A, in the treatment of retinitis pigmentosa, an inherited disease, is able to help alleviate the disorder so that patients can keep their sight longer. They also showed that vitamin A was instrumental in preventing night blindness, Bitot’s spots, corneal lesions, and photophobia.
The delicate tissues surrounding the eyes and eyelids, as well as the actual eye itself, need vitamin A and vitamin C in order to maintain optimal health. The frequent appearance of styes usually indicates a vitamin A deficiency. Since Vitamin A is used up quickly when the eyes are exposed to glare or bright lights, it is an especially important that this nutrient be supplemented for those do much driving, work outdoors in the bright sun, or work with glary-white paper.
A study at the University of Illinois suggests that daily consumption of fruits and vegetables rich in Vitamin A may be linked to a lower risk of macular degeneration. Also, the risk seemed to decrease with each additional day that fruits and vegetables were consumed. Those who regularly ate five servings or more of dark green leafy vegetables each week, foods rich in the carotenoids lutein and zeaxanthin, had markedly lowered their risk of developing macular degeneration than did participants who ate smaller amounts or none of these vegetables. There is some evidence that taking lutein supplements has a similar benefit.
Vitamin A is found mainly in such yellow vegetables as carrots and yams. The darker the orange color, the higher the content of vitamin A. Vitamin A is also stored in the body for long periods of time in the liver. Supplements of vitamin A are best taken in the form of beta carotene; otherwise, it is possible to develop a toxicity. However, with beta carotene supplementation, the body is able to store it without any risk of toxicity.
Vitamin A is also an antioxidant. This means it is a free radical destroyer. Free radicals attack the structural proteins, enzymes, and cell membranes of the eye. Antioxidants are those vitamins, minerals, and enzymes that help maintain healthy cells and tissues by combating free radicals in the bloodstream.
Free radicals are unstable oxygen molecules, and under normal circumstances, perform a number of valuable functions. However, a surplus can damage normal cells and play a role in the development of cataracts, macular degeneration, and glaucoma, as well as a host of other diseases, including cancer and cardiovascular disease. Some studies are showing that anthocyanin, another antioxidant, may improve night vision.
Although vitamin supplements are acknowledged as being vital for eye health, as well as health of the body in general, most doctors are skeptical when it comes to the possibility of them preventing or curing any disorder or disease. They are learning though, just as the rest of the public has been doing over the years.
The following are some other nutrients known to prevent, slow the progression of, or cure some common eye problems.
Vitamin C is found in high concentrations in the aqueous humor. It is vital for maintaining normal vision and for keeping the capillaries and connective tissues of the eye in good working order.
- Large doses of vitamin C have proven to be effective in drawing fluid away from the eye and reducing elevated intraocular pressure (IOP) associated with glaucoma.
- Vitamin C may be effective in the prevention of cataracts and such retinal disorders as diabetic retinopathy and age-related maculopathy. Since cataracts and retinal damage may be caused by an excess of free radicals and since vitamin C is an antioxidant, a diet containing this vitamin may slow the process of developing cataracts or retinal disorders.
- Retinitis is a disease commonly associated with diabetes. Its perceptive structure, as well as other complaints associated with capillary fragility, have responded well to the administration of bioflavinoid-vitamin C therapy.
- Scurvy is a well-known result of vitamin C deficiency, which then leads to ocular hemorrhage. Any hemorrhage of the eye not related to diabetes, hypertension, or another cause, should be investigated as a symptom of scurvy. Vitamin C treatments usually produce results within a week.
Zinc is one of the most common trace minerals in the body and is highly concentrated in the retina. Zinc allows vitamin A to be released from the liver and is used in the process of metabolism in the retina. Since a zinc deficiency prevents the body from using any available vitamin A, it may cause the same effects as a vitamin A deficiency.
- It is speculated that a deficiency of zinc contributes to macular degeneration and retinal detachments.
- Zinc, as well as copper, deficiencies may also be linked to the formation of cataracts.
Amino Acids are the “building blocks” of protein. Protein deficiencies show up under a myriad of complaints, and vision is no exception. Frequently, it is in the form of “bags under the eyes.” Specific amino acid deficiencies and their contribution to eye health, or the lack thereof, are as follows:
- Taurine is found in high concentrations in the eye. It is the most abundant amino acid in the retina of all species studied. Cats, which make less of their own taurine than humans, may become blind on taurine or methionine deficient diets. This blindness, usually in kittens, is caused by degeneration of the light-sensitive cells in the eye. It can be reversed if caught early enough and the animal’s diet is supplemented with taurine. Although there have not yet been any reports of taurine-deficiency blindness in humans, it has been found that people suffering from retinitis pigmentosa show abnormal blood levels of taurine. Decreased taurine levels within the eye have been linked to this disease. Taurine is also known to protect the body, as well as the eye, from various toxins.
- Lysine is neccesary for collagen formation in tissue needed for lens repair. It also neutralizes viruses implicated in lens damage.
- Experiments on animals have produced the following results: animals missing either histidine or phenylalanine in their diets developed pre-cataract conditions, that is, a widening of the sutures, separation of fiber cells, and haziness of the lens. Diets missing histidine will produce cataracts in three weeks. Diets lacking leucine, threonine, isoleucine,valine, lysine, or any sulfur amino acid produced eye defects but did not produce blatant cataracts.
- Glutathione is is a tri-peptide of glutamic acid, cysteine, and glycine. It is not considered a true amino acid, but does have a close enough relationship to them to be included. It is a powerful antioxidant that inhibits the formation of free radicals. Glutathione is found in particularly high concentrations in the cornea and lens of the eye, where it seems to help keep the lens transparent, protecting against cataracts. Testing further revealed that riboflavin deficiency, as previously mentioned, is a factor in cataract formation because the riboflavin-dependent enzyme glutathione reductase decreases when glutathione is deficient. With the presence of another amino acid called cysteine, eliminated the effects of riboflavin deficiency, probably because it is able to increase gluthathione.
B-complex vitamins, also known as the anti-stress vitamins, are important for intracellular eye metabolism. Treatment with adequate dosages of these vitamins usually reverses or improves conditions.
- B-complex deficiency contributes to overall vision loss.
- B-complex vitamins with extra riboflavin (B-2) has been used to improve farsightedness and generally improves intraoccular celluar metabolism.
- Riboflavin (B2), pantothenic acid (B5), and thiamine (B1) deficiency have been linked to cataract formation.
- Since a deficiency of thiamine (B1) affects the optic nerve, this means an interruption or an interference with messages. This condition, referred to as nutritional amblyopia, produces scotomas (blind spots) in the field of vision. Thiamine supplements can often correct and restore vision lost due to this deficiency.
- Vitamin B2 (riboflavin) deficiency may cause cornea disease or keratitis.
- Vitamin B6 (pyridoxine) deficiency may cause vascular congestion and corneal neovascularization.
- Vitamin B12 deficiency, or pernicious anemia, is associated with retrobulbar neuritis (swelling of the optic nerve).
- Eyes that are dry and scaly at the corners, indicate a deficiency of riboflavin (B2) and B6. Improvement is noted after these nutrients have been restored to the diet.
Vitamin E is another antioxidant nutrient. Studies suggest that both vitamin E and vitamin C may slow the growth of cataracts.
Iron deficiency is the cause of one type of anemia, which often shows up as “pale eyes.”
Combinations of nutrients often help in certain cases.
- For instance, in the case of herpes zoster (Shingles) near the eye or on the face, treatment by an ophthalmologist is required in order to prevent damage to the cornea. Helpful treatments include high-potency B-complex vitamins with extra B12 and vitamin E. Applying zinc oxide cream to the blisters and affected areas may also help. After the blisters are healed, aloe gel and vitamin E applied to the areas to speed healing and prevent scarring. If all of this shows little improvement within three days, injections of 25 grams of Vitamin C brings relief almost immediately.
- Calcium and magnesium, in a minimal ratio of 2:1, help microcirulation in the eye. Such other problems as retinal vascular leakage, microaneurisms, and retinal edema have responded well to nutritional supplements of calcium and magnesium.
- Gary Price Todd was an ophthalmologist who discovered than many diseases of the eyes. For example, cataracts and macular degeneration, can be treated effectively with appropriate nutritional supplements. He suggested taking a multivitamin and mineral supplement the night before eye surgery, with an additional 10,000 IU of Vitamin A (beta carotene form is best), 1000 mg of vitamin C, and 1200 mg of vitamin E. However, do not take this amount if you have high blood pressure or have never taken vitamin E before. Always start with 400 mg, or less, of Vitamin E and work up gradually. After surgery, Dr. Todd recommended the continued use of these vitamins, plus adding 2 mg of copper and at least 20 mg of zinc to help speed healing.
- Research indicates that proper nutrition is an important factor in the prevention of cataracts. Deficiencies of vitamins A, C, B-2, B-6, E, panothenic acid, and calcium may all contribute to cataract formation. In addition, copper, manganese, selenium, and zinc are minerals important for proper healing and for retarding the growth of cataracts. Therefore, it seems to be important to have a nutritious diet in order to prevent cataract formation.
- Conjunctivitis treatment includes large doses of vitamins A and C, as well as zinc, which promote rapid healing and increases immunity.
- Deficiencies of vitamins A, B, C, and trace minerals, are known to increase the risk of glaucoma.
- Supplements of vitamins A, C, and E may be prescribed in combination to retard the progression of diabetic retinopathy, age-related maculopathy, and cataracts. They also help maintain the health of blood cells and vessels of the retina and assist in the healing process after surgery.
On the other hand, an excess of vitamin D2 may cause opacities in the cornea or conjunctiva and scleral calcification. Overdose in infancy may produce optic atrophy, optic neuritis, or convergent strabismus. However, overdosing on this vitamin is extremely hard to do, especially if taking vitamin D3.