Cataracts - 1
Agatha M. Thrash, M.D.
Cataracts develop when damage to the protein of the lens of the eye clouds the lens and impairs vision.
Most people who live long enough will develop cataracts. Cataracts are more likely to occur in those who smoke, have diabetes, or are exposed to excessive sunlight. All of these factors lead to oxidative damage. Oxidative damage to the lens of the eye appears to cause cataracts in animals and people.
It is unlikely that any nutritional supplements or herbs can reverse existing cataracts.
Checklist for Cataracts
- Reliable and relatively consistent scientific data showing a substantial health benefit.
- Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
- An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.
What are the symptoms of cataracts? Cataracts usually develop slowly without any pain or redness of the eye. The most common symptoms of a cataract are fuzzy or blurred vision, increasing need for light when reading or doing other close work, visual disturbances caused by bright lights (e.g. sunlight, car headlights), faded color perception, poor night vision, and frequent need to change eyeglass or contact lens prescriptions. A cataract will not spread from one eye to the other, although many people develop cataracts in both eyes.
Conventional treatment options: In the beginning stages, the use of magnifying lenses, stronger eyeglasses, and brighter lighting may compensate for the vision problems caused by cataracts. Once vision is no longer adequate for daily activities, a doctor may recommend surgery to remove the clouded lens and replace it with a clear artificial lens. In many people, the lens capsule remaining in the eye after surgery eventually turns cloudy, causing additional loss of vision.
Lifestyle changes that may be helpful: Obese men are significantly more likely to develop a cataract than are men of normal body weight. To date, most but not all population studies have found an increased risk of cataracts as body mass increases.
Nutritional supplements that may be helpful: People with low blood levels of antioxidants and those who eat few antioxidant-rich fruits and vegetables have been reported to be at high risk for cataracts.Vitamin B2 and vitamin B3 are needed to protect glutathione, an important antioxidant in the eye. Vitamin B2 deficiency has been linked to cataracts. Older people taking 3 mg of vitamin B2 and 40 mg of vitamin B3 per day were partly protected against cataracts in one trial. However, the intake of vitamin B2 in China is relatively low, and it is not clear whether supplementation would help prevent cataracts in populations where vitamin B2 intake is higher.
The major antioxidants in the lens of the eye are vitamin C and glutathione (a molecule composed of three amino acids). Vitamin C is needed to activate vitamin E which in turn activates glutathione. Both nutrients are important for healthy vision. People who take multivitamins or any supplements containing vitamins C or E for more than 10 years have been reported to have a 60% lower risk of forming a cataract.
Vitamin C levels in the eye decrease with age. However, supplementing with vitamin C prevents this decrease and has been linked to a lower risk of developing cataracts. Healthy people are more likely to take vitamin C and vitamin E supplements than those with cataracts according to some, but not all studies. Dietary vitamin C intake has not been consistently associated with protection from cataracts. Nonetheless, because people who supplement with vitamin C have developed far fewer cataracts in some research, doctors often recommend 500 to 1,000 mg of vitamin C supplementation as part of a cataract prevention program. The difference between successful and unsuccessful trials may be tied to the length of time people actually supplement with vitamin C. In one preliminary study, people taking vitamin C for at least 10 years showed a dramatic reduction in cataract risk, but those taking vitamin C for less than ten years showed no evidence of protection at all.
Low blood levels of vitamin E have been linked to increased risk of forming cataracts. Dietary vitamin E intake has not been consistently associated with protection from cataracts. Vitamin E supplements have been reported to protect against cataracts in animals and people, though the evidence remains inconsistent. In one trial, people who took vitamin E supplements had less than half the risk of developing cataracts, compared with others in the five-year study. Doctors typically recommend 400 IU of vitamin E per day as prevention. Smaller amounts (approximately 50 IU per day) have been proven in double-blind research to provide no protection.
Some, but not all studies have reported that people eating more foods rich in beta-carotene had a lower the risk of developing cataracts. Supplementation with synthetic beta-carotene has not been found to reduce the risk of cataract formation. It remains unclear whether natural beta-carotene from food or supplements would protect the eye or whether beta-carotene in food is merely a marker for other protective factors in fruits and vegetables high in beta-carotene.
People who eat a lot of spinach and kale, which are high in lutein and zeaxanthin, carotenoids similar to beta-carotene, have been reported to be at low risk for cataracts. Lutein, zeaxanthin, and beta-carotene offer the promise of protection because they are antioxidants. It is quite possible, however, that lutein is more important than beta-carotene, because lutein is found in the lens of the eye, while beta-carotene is not. In one preliminary study, lutein and zeaxanthin were the only carotenoids associated with protection from cataracts. People with the highest intake of lutein and zeaxanthin were half as likely to develop cataracts as those with the lowest intake.
The flavonoid, quercetin may also help by blocking sorbitol accumulation in the eye. This may be especially helpful for people with diabetes, though no clinical trials have yet explored whether quercetin actually prevents diabetic cataracts.
Are there any side effects or interactions? Refer to the individual supplement for information about any side effects or interactions.Herbs that may be helpful: Bilberry, a close relative of blueberry, is high in flavonoids called anthocyanosides. Anthocyanosides may protect both the lens and retina from oxidative damage. The potent antioxidant activity of anthocyanosides may make bilberry useful for reducing the risk of cataracts. Doctors sometimes recommend 240 to 480 mg. per day of bilberry extract, capsules, or tablets standardized to contain 25% anthrocyanosides.
Are there any side effects or interactions? Refer to the individual herb for information about any side effects or interactions.
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