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Vision Nutrition

Many nutritional compounds are important in vision, both for protecting the eye from damage as well as in the actual process of vision. Although many aspects of vision remain a mystery, it is known that in order for normal vision to occur, light must interact with the specialized nerve cells of the eye--rods and cones--to create a nerve impulse. The nerve impulse is then transmitted to the visual areas of the brain.

The health of the eye is largely dependent on a rich supply of nutrients and oxygen. Relatively speaking, the amount of blood flow through the eye is the greatest in the body. This high blood flow highlights the importance of nutrition and the circulatory system for optimal eye health and function. When normal mechanisms which deliver oxygen and other nutrients to the eye, or the eye's protective devices, begin to fail, a variety of disorders develop. These include cataracts and macular degeneration. These disorders are almost always associated with aging.

Cataracts are the leading cause of impaired vision and blindness in the United States. Approximately four million people have some degree of vision-impairing cataract, and at least 40,000 people in the United States are blind because of cataracts. Cataracts are also a source of tremendous financial burden on our society: cataract surgery is the most common major surgical procedure done in the United States each year (600,000 per annum) for persons on Medicare at a cost of over $4 billion.

The macula is the portion of the eye responsible for fine vision. Degeneration of the macula is the leading cause of severe visual loss in the United States and Europe in persons aged 55 years or older. The risk factors for macular degeneration include aging, atherosclerosis, and high blood pressure. There is no current medical treatment for the most common form of macular degeneration. Laser surgery is used for those who develop a less common type of macular degeneration, known as exudative macular degeneration.

The origin of cataract formation and macular degeneration is ultimately related to damage caused by compounds known as free radicals. In essence, a free radical is a highly reactive molecule that can bind to and destroy body components. Free radical or "oxidative" damage is what makes us age. In addition to their role in causing cataracts and macular degeneration, free radicals have also been shown to be responsible for the initiation of many diseases including the two biggest killers of Americans--heart disease and cancer.

As with most diseases, prevention or treatment of cataract or macular degeneration at an early stage is more effective than trying to reverse the disease process. Since free radical damage appears to be the primary factor, individuals with cataracts should avoid direct sunlight, bright light, and wear protective lenses (sunglasses) when outdoors. In addition, individuals with either cataracts or macular degeneration should also greatly increase intake of dietary compounds known as antioxidants which prevent free radical damage.

The best foods to prevent cataracts and macular degeneration are fruits and vegetables. Numerous studies have shown that individuals consuming more fruits and vegetables are less likely to develop cataracts or macular degeneration compared to individuals who do not regularly consume fruits and vegetables. Fresh fruits and vegetables are rich in a broad range of antioxidant compounds including vitamin C, carotenes, flavonoids, and glutathione. All of these antioxidants are critically involved in important mechanisms which prevent the development of cataracts and macular degeneration.  (top)

For example, the antioxidant compound glutathione is found in very high concentrations in the lens where it plays a vital role in maintaining a healthy lens. Specifically, glutathione functions as an antioxidant, maintains the structure of the lens proteins, acts in various enzyme systems, and participates in the transport of nutrients into the lens. Glutathione levels are diminished in lenses that have cataracts.

Therefore, it is a good idea if you are developing a cataract to make sure that you have a good intake of glutathione. Try and eat your fruits and vegetables in their fresh uncooked form. This is because the glutathione content of fresh fruits and vegetables is substantially higher than their cooked counter parts.

It would be best for the individual with either a cataract or macular degeneration to supplement their diet with additional antioxidant nutrients like vitamin C, vitamin E, zinc, selenium, glutathione, and NAC, or N-acetyl-cysteine (a precursor to glutathione). Vitamin C appears to be especially important, as clinical studies have demonstrated that vitamin C can actually halt cataract progression. In one study, 450 patients with cataracts were placed on a nutritional program that included 1 gram of vitamin C per day, resulting in a significant reduction in cataract development. More recent information indicates that a dose of at least 1,000 mg. of vitamin C is needed to increase levels of this nutrient in the eye.

For years it has been thought that beta-carotene is important for eyesight. Recently other carotenoids, such as lutein and zeaxanthin, have come to the forefront in nutritional research on vision. Lutein occurs naturally at higher levels than beta-carotene in many fruits and vegetables, and both lutein and zeaxanthin are found in the macular region of the eye.

Researchers have recently found evidence that consumption of lutein and zeaxanthin correspond to a decreased risk for age-related macular degeneration (AMD). They theorize that lutein and zeaxanthin have this effect by reducing free-radical damage caused by high energy light from the blue end of the spectrum, especially damage to lipid components of the retina. The use of antioxidant supplements for treatment or prevention of AMD are also supported by a study published in the Journal of the American Optometric Association (January, 1996), which showed that a group of U.S. veterans in their 70's taking TwinLab OcuGuard Caps halted the progression of advanced AMD, compared to a control group which experience further loss of vision. (TwinLab now also offers OcuGuard Plus Lutein.)  (top)

The eye contains a vast number of photosensitive cells called receptors. When light strikes the receptors a photo chemical process is mediated by a pigment, rhodopsin (visual purple), creating nerve impulses transmitted to the brain via the optic nerve. Bright light decomposes the visual purple. For example, working at a computer terminal screen, the eyes tire as the visual purple is quickly broken down under the influence of bright light. Regeneration of visual purple is a slow process. However, bilberries contain anthocyanosides, an agent that accelerates the production of rhodopsin.

Bilberry (Vaccinium myrtillus) or European blueberry is a blue-black berry that differs from an American blueberry in that its meat is also blue-black. Interest in bilberry was first aroused when it was observed during World War II that British Royal Air Force pilots reported improved nighttime visual acuity on bombing raids after consuming bilberries. Later studies showed that administration of bilberry extracts to healthy subjects resulted in improved nighttime visual acuity, quicker adjustment to darkness, and faster restoration of visual acuity after exposure to glare.

The active components of bilberries are flavonoids known as anthocyanosides. The anthocyanosides are potent antioxidants and also work to improve blood flow to the eye. In Europe, bilberry extracts are now part of the conventional medical treatment of many eye disorders including cataracts and macular degeneration, as well as retinitis pigmentosa, diabetic retinopathy, and night blindness. This use is supported by repeated positive results in controlled clinical trials.

Research tells us that there are many ways to protect the eye from damage and disease. Preventing or halting the progression of cataracts and macular degeneration can be helped by the combination of a diet rich in fresh fruits and vegetables, and supplementation with nutrients such as vitamins C and E, beta-carotene, lutein, zeaxanthin, bilberry extract, glutathione, NAC, selenium and zinc.



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