Vitamins C and E are anti-oxidants that prevent damage to the eye resulting from a lifetime of normal metabolism and exposure to UV radiation. These two nutrients can decrease the risk and reduce progression of macular degeneration and cataracts which are, in part, caused by free radical damage.
First, What are Anti-oxidants?
Antioxidant means: Anti– (from Latin) is “against,” “opposed to” and oxidant refers to reactive molecules produced during the body’s oxygen metabolism or created from environmental causes. Antioxidants, therefore, are those molecules responsible for reducing those reactive molecules which are free radicals and oxidants. Free radicals and oxidants have been implicated as one of the causes of disease.
The body uses oxygen for many of its biological functions, like enzyme reactions, immune response, producing energy, and the biochemical reactions that create vision. Free radicals and oxidants are created as a by-product of these reactions.
Free radicals and oxidants in the body are created two ways:
- As a normal by-product of cell metabolism, or
- from external assaults to the body, like radiation and UV light, cigarette smoke, pollution, or medications.
The body can create its own antioxidants, but when there is an imbalance, meaning there are more free radicals then there are antioxidants, a phenomenon called oxidative stress occurs.
Oxidative stress means there is a surplus of these reactive particles running around which have the capability to attack healthy cells. Healthy cells under oxidative stress become dysfunctional resulting in degeneration. Degeneration results in aging and disease.
How to Get More Anti-oxidants:
The body combats oxidative stress by producing its own antioxidants and utilizing foods as a source of naturally occurring antioxidants. The role of the antioxidant is to “scavenge” for free radicals to prevent cellular damage. When an imbalance exists, and the body is under oxidative stress, and a nutritional diet does not supply enough antioxidants, supplementation is necessary.
Clinical Studies and Antioxidants
While most studies of eye disease agree that oxidative stress in the eye is a cause of the degenerative diseases of macular degeneration and cataracts, the role of antioxidants is less certain.
Macular Degeneration. The macula, which is responsible for seeing the fine line and detail of the central vision, consumes a lot of oxygen and is assaulted by UV light radiation. For these reasons this very sensitive area is predisposed to oxidative stress. Long-term oxidative stress, without anti-oxidants to combat free radicals and oxidative products, results in age-related eye disease.
Vitamin C and Vitamin E are two antioxidant vitamins studied because it is thought that they may prevent and protect the macula from oxidative damage.
Cataracts. The lens of the eye not only serves to focus the light to the macula, but also serves to absorb UV light. It is the light radiation that creates oxidative stress within the lens that results in cataracts. While it is not certain what the role antioxidants supplements play in reducing the risk for cataracts, it is known that the levels of vitamin C decrease with age, suggesting that cataracts increase as antioxidants in the lens decrease
Dietary Sources of Antioxidants
Nothing new here: a nutritious diet rich in fruits and vegetables.
The Essential Vitamin C
While vitamin C is one of many antioxidants, it is a nutrient that is important to many biochemical reactions in the body and is essential for overall health and is considered to have an anti-aging effect. It is an essential antioxidant which scavenges for those free radicals produced by the body’s metabolic activity and environmental attacks to reduce oxidative stress. It is crucial for cardiovascular health, supports the immune system, and nerve cell function.
Vitamin C is one of the water soluble vitamins. This means that it is not stored in the body as reserves for future use. Because it is not stored, it needs to be ingested on a regular basis. Water soluble also means that any excess vitamin C is excreted into the urine.
Vitamin C and Cataracts
While cataracts are a part of the aging process, and cannot be completely prevented, Vitamin C has been studied as a nutrient effective in delaying and reducing the progression of cataract formation. It is thought to reduce the oxidative stress within the lens, which is created by the absorption of UV light radiation. Studies indicate that the level of vitamin C within the lens decreases with age. This decrease is hypothesized to contribute to age-related cataract formation
Vitamin C and the Retina
Vitamin C supports nerve health of the brain and the eye (which is an extension of the brain.) Studies have shown that nerve tissues concentrate vitamin C, which is an essential part of nerve functioning and reduction of oxidative stress within the nerve tissue. It is thought that this nutrient is essential for both brain and eye nerve health. The implication is that vitamin c may help protect the retinal cells of those with age-related macular degeneration, glaucoma, and diabetic retinopathy.
Dietary Sources of Vitamin C
Vitamin C is also known as ascorbic acid. It is most often associated with citrus fruits and tangy orange chewable vitamin supplements. Vitamin C is not only found in citrus fruits (that is oranges, lemons, limes, grapefruits), but other fruits such as mangos, kiwis, papaya, melon, and berries, such as strawberries. Vitamin C can also be found in vegetables, such as yellow bell peppers, broccoli, and tomatoes.
Supplementing Vitamin C
Daily recommended dosages are between 75 – 2000 mg/day (Mayo Clinic). This wide range is dependent on age, health status, and diet. In the previously discussed AREDS study, which evaluated the effect of vitamin supplementation on the progression of macular degeneration, the dosage of vitamin C in the study was 500 mg/day.
Those who need to supplement their diet with vitamin C are:
- Smokers and alcoholics,
- older adults:
- those with poor circulation,
- those with digestive disease,
- those with liver disease, and
- those with a nutritionally deficient diet.
The Antioxidant Vitamin E
Vitamin E refers a group of fat soluble chemicals. While there are several forms, alpha- tocopherol is the form that the body recognizes as a nutrient. It is an important antioxidant to reduce the damage caused by free radicals and it is thought to help strengthen the immune system, blood, and cell membranes.
Dietary Sources of Vitamin E
Keep in mind that alpha-tocopherol is fat soluble indicating that dietary fats are a good source. Foods such as vegetable oils like olive, corn, and safflower oils, as well as the oils in nuts, seeds, and wheat germ. Almonds and sunflower seeds are known as sources high in vitamin E.
Vitamin E and Eye Health
The role vitamin E plays in the eye is one of protection as an antioxidant and support for nerve health.
Macular Degeneration. The retina is sensitive to changes in vitamin E levels. Cell membranes of retinal nerves are lipid based and are subject to lipid oxidation by free radicals. Vitamin E is thought to play a role in reducing the risk for progression of AMD by reducing lipid oxidation. It also reduces platelet aggregation (anti-coagulant) for maintenance of blood flow.
Vitamin E Supplementation
When listed on Supplement Facts labels, vitamin E is indicated by IU, which is International Units. This is a measurement indicating biological activity, not an actual measurement of the amount of vitamin E, which differs from when it is listed in milligrams (mg).
The American Food and Drug Administration does not require food labels to indicate the amount of vitamin E. The recommended dietary allowance (RDA) is 15 mg (22.4 IU) to 19 mg (28.4 IU). Most multivitamins have 22 to 38 IU. Supplements indicated as ‘Vitamin E’ will have as much as 400 IU. Vitamin E also comes in both natural and synthetic forms. The synthetic form is indicated as dl-alpha- tocopherol. No harm in ingesting the synthetic form, but it is thought not to be absorbed or utilized as readily as the natural, which is indicated as d-alpha-tocopherol (acetate or succinate).
Those who should be cautious about supplementing their dietary intake with vitamin E:
Those who receive treatments or medications which cause blood thinning, as high doses of vitamin E cam exacerbate blood thinning:
- Anticoagulant and antiplatelet medications
- Simvastatin and niacin
- Chemotherapy and radiotherapy.
A Well Known Study of Anti-oxidants Vitamin C and E, and Macular Degeneration and Cataracts
Vitamins C and E were a part of the Age-Related Eye Disease Study 2 (AREDS 2), which evaluated the effect of supplementing with vitamin C, E (400 IU/day), zinc, lutein, and zeaxanthin on the progression of age-related macular degeneration and cataracts.
The progression of AMD was decreased by 25% with this combination of supplements. The thought is that AMD is, in part, a result of poor nutrition. The importance of this study was that it showed that nutritional intervention can make a difference in reducing the progression of age=related eye disease.
Learn more about the AREDS 2 study:
Other Anti-oxidant Nutrients s for Ocular Health:
- Carotenoids, esp: lutein, zeaxanthin, and meso-zeaxanthin
- Flavonoids, esp: Anthocyanins
- Fatty acids: Omega 3, DHA and EPA
In the End…
The eye is particularly susceptible to age-related eye disease because of its high metabolic rate and exposure to UV radiation. The risk increases as we age. Dietary intake of these essential nutrients often falls below recommended levels. Anti-oxidants are key to not only decreasing the progression of age-related eye disease but important for prevention.
As with any other supplements, check with your doctor before launching into a supplement regiment high in antioxidants. While antioxidants are necessary for protection and prevention of disease, excessive dosing of some can be harmful.
Other important supplements for eye health: