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- Unclear or Conflicting Scientific Evidence:
[Beta-carotene]: Beta-carotene is a member of the carotenoids, which are highly pigmented (red, orange, yellow), fat-soluble compounds naturally present in many fruits, grains, oils, and vegetables (green plants, carrots, sweet potatoes, squash, spinach, apricots, and green peppers). Study results of beta-carotene supplementation for cataract prevention are conflicting. Further well-designed clinical trials are needed before a conclusion can be drawn. Supplemental beta-carotene may increase the risk of lung cancer, prostate cancer, intracerebral hemorrhage, and cardiovascular and total mortality in people who smoke cigarettes or have a history of high-level exposure to asbestos. Beta-carotene from foods does not seem to have this effect. In those who smoke, beta-carotene may increase cardiovascular death, including heart attack.
[Bilberry]: Bilberry (Vaccinium myrtillus) is a close relative of the blueberry. Bilberry extract has been used for a number of eye problems, including the prevention of cataract worsening. At this time, there is limited scientific information in this area. Bilberry may increase bleeding in sensitive individuals, such as those taking blood thinning medications including warfarin (Coumadin ®) and aspirin.
[Kinetin]: Kinetin is a chemical analogue of cytokinins, a class of plant hormones that promotes cell division. Kinetin is found in both plants and animals. Side effects of cataract surgery may include pain, infection, swelling, bleeding, or retinal detachment. The use of kinetin during cataract surgery may lower adverse effects associated with cataracts. More research is needed in this area.
[Lutein]: Lutein and zeaxanthin are found in high levels in foods such as green vegetables, egg yolk, kiwi fruit, grapes, orange juice, zucchini, squash, and corn. For some commercially available supplements, lutein is extracted from marigold petals. Human study has not found a benefit of lutein supplementation on visual performance in people with cataracts. More information is required.
[Riboflavin (vitamin B2)]: Riboflavin is a water-soluble vitamin that is involved in vital metabolic processes in the body, and is necessary for normal cell function, growth, and energy production. Small amounts of riboflavin are present in most animal and plant tissues. It has been suggested that low riboflavin levels may be a risk for developing cataracts, or that riboflavin supplementation may be beneficial for prevention. Additional evidence is needed before a clear conclusion can be drawn.
[Selenium]: Selenium is a trace mineral found in soil, water, and some foods. It is an essential element in several metabolic pathways. Preliminary research reports that selenium supplementation may affect the development of cataracts. Further research is needed before a clear conclusion can be drawn.
[Thiamin]: Thiamin, also known as thiamine and vitamin B1, is a water-soluble B-complex vitamin. Preliminary evidence suggests that high dietary thiamin intake may be associated with a decreased risk of cataracts. Further evidence is necessary before a firm conclusion can be reached.
[Vitamin A]: Vitamin A is a fat-soluble vitamin, which is derived from two sources: preformed retinoids and provitamin carotenoids. Retinoids such as retinal and retinoic acid are found in animal sources such as liver, kidney, eggs, and dairy produce. Carotenoids like beta-carotene (which has the highest vitamin A activity) are found in plants such as dark or yellow vegetables and carrots. Vitamin A has been suggested to prevent cataract formation. Carotenoids such as beta-carotene, lutein, and zeaxanthin may decrease the risk of severe cataracts. There is not sufficient evidence to form a clear conclusion at this time. Vitamin A should only be used within the recommended dietary allowance, because vitamin A excess, as well as deficiency, have been associated with birth defects. Excessive doses of vitamin A have been associated with central nervous system malformations.
[Vitamin E]: Vitamin E is a fat-soluble vitamin with antioxidant properties. There is conflicting evidence regarding the use of vitamin E to prevent cataracts. Although some studies across populations have suggested some protective effects (which may take up to 10 years to yield benefits), other studies in humans report a lack of benefits when used either alone or in combination with other antioxidants. Additional research is necessary before a clear conclusion can be reached. Vitamin E may increase bleeding in sensitive individuals, such as those taking blood thinning medications including warfarin (Coumadin ®) and aspirin.
- Traditional or Theoretical Uses Lacking Sufficient Evidence:
- Integrative therapies used in cataracts that have historical or theoretical uses but lack sufficient clinical evidence include: acupuncture, chelation (EDTA) therapy, coleus (Coleus forskohlii), copper, detoxification therapy, dogwood (Cornus spp.), eyebright (Euphrasia officinalis), fenugreek (Trigonella foenum-graecum), ginkgo (Ginkgo biloba), green tea (Camellia sinensis), holy basil (Ocimum sanctum), honey, lycopene, niacin (vitamin B3), onion (Allium cepa), pantethine, quercetin, rehmannia (Rehmannia glutinosa), rosemary (Rosmarinus officinalis), turmeric (Curcuma longa) and curcumin, and vitamin O (oxygen).
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