How do we see?

Sight begins as light passes through the cornea to the lens, focusing light onto the retina at the back of the eye (especially the macula and the fovea, which is at the very center of the retina).  The retina’s nerve receptors are stimulated by light and send impulses to the brain where they are converted into mental images.  Nutrition plays a critical role in all aspects of vision — including the ability to focus and to see at night, and the defense of delicate tissues of the lens and retina against oxidative damage.*

Poor Vision Explained

Poor vision is a serious problem which many people face as they age. Annual medical costs for eye care in America exceed 3 billion dollars in Medicare funds alone. Eighteen percent of Americans over age 65 and forty-six percent over age 75 have been found to have clouded lenses which obscure their vision.1,2  Approximately twenty-five percent of Americans over age 65 experience damage to their retinas which reduces their ability to see clearly.3  Several lifestyle factors such as smoking, diabetes, injury, steroids, excess exposure to smoke, air pollution, sunlight or radiation, and simply growing older can damage cells in the eye. That’s because most of these factors create dangerous free radicals, which can result in poor eyesight. Free radicals in the eye are tiny particles created by light that react with other substances in the eye, causing damage.

Maintaining a Healthy Eye

The ability to see is a tremendous gift, and it all depends on a delicate balance of exquisitely designed parts. One of the keys to maintaining a healthy eye lies in proper nutritional support for the retina and the lens. Specific nutrients are required for each part to work properly.  Nature’s Life offers two comprehensive formulas to provide these essential vitamins, minerals and phytonutrients to help protect our eyes from damaging free radicals by neutralizing, or “scavenging” them.*

People with low blood levels of antioxidants or who eat limited amounts of antioxidant-rich fruits and vegetables are more likely to lose the transparency found in healthy lenses.4,5  Two research groups found that people with healthy maculae were more likely to have high blood levels of antioxidants.6,7

The Role of Beta Carotene

Beta carotene, often called the “safer” form of vitamin A, is a powerful antioxidant nutrient.  In the Nurse’s Health Study, published in 1992, foods high in beta carotene were linked to the maintenance of transparent lenses.*8 People in this study who supplemented with extra beta carotene for over ten years were much more likely to have healthy lenses.*6  Low blood levels of beta carotene were clearly associated with a higher risk for developing clouded lenses.*6

Antioxidant protection from light-induced damage may be an important part of beta carotene’s function in protecting the macula.* Researchers report that people who eat a diet high in beta carotene and other carotenoids have less damage to their macula.*9 This protective effect has also been reported for total carotenoids including alpha carotene, cryptoxanthin, lutein and zeaxanthin.*7

Lutein & Zeaxanthin

Lutein and zeaxanthin are carotenoids (like beta carotene) found abundantly in spinach, kale, broccoli, green leafy vegetables, papayas and mangos.10  They are not easily converted to vitamin A (like beta carotene) but they do have potent antioxidant activity.*  These carotenoids concentrate in the yellow pigment in the retina and appear to specifically protect the macula and fovea against oxidative damage.*7 Researchers have discovered two important facts about these carotenoids:

1.   The body works hard to concentrate lutein and zeaxanthin in the macula and fovea of the retina.11

2.   Lutein and zeaxanthin provide potent antioxidant protection against singlet oxygen free radicals which damage the macula and fovea.*11

    A multicenter Eye Disease Case-Control Study looked at the relationship between lutein, zeaxanthin and protection of the macula.  People eating a total of 5.8 mg per day of lutein and zeaxanthin from dietary sources are much more likely to have healthy, undamaged macula.*7  That’s the equivalent of about 3 cups of chopped fresh spinach every day!

Vitamins

In two studies, people with healthy, clear, transparent lenses were more likely to be taking vitamin C and vitamin E supplements than were people with clouded lenses.*8,12,13  Researchers found that people who supplemented with at least 300 mg of vitamin C enjoyed a 50-70% decrease in the risk for clouding of the lens.*12 Both studies found these associations with supplements, not just from vitamin-C rich foods.

A Canadian study tested 152 people with clear lenses and 152 people with clouded lenses and found that those  taking vitamin E supplements had 56% less risk of clouded lenses.*12  This study showed that the more vitamin E taken the greater the level of lens protection.*  This “dose/response relationship” is considered to be powerful scientific evidence. Vitamin E also helps maintain levels of the important antioxidant glutathione.*14  While the association between high intake of vitamin E supplements and lens clarity has recently been confirmed,15 supplements of only 50 IU per day of vitamin E have not been found to be effective.*16

Vitamin B2 (Riboflavin) is generally not thought of as an antioxidant, but the antioxidant glutathione needs enough vitamin B2 so it can be reactivated as glutathione reductase (an important antioxidant enzyme).*  When levels of glutathione reductase fall, the lens loses its transparency.*17

In China, people with healthy lenses were given daily doses of 3 mg of B2 and 40 mg of B3 (Niacin) or a placebo and followed for years. At the end of the study, those taking the B vitamins were much more likely to have maintained normal lens clarity and transparency.*18

Visionary Minerals

 In terms of eye health, the main function of zinc is to activate two critical enzymes, retinol dehydrogenase and catalase,19 which are used to mobilize stored vitamin A from the liver and convert it, thus allowing “seeing” to occur.* Insufficient zinc reduces blood levels of vitamin A, which can impair vision.* The inability of people with liver damage to see well at night has been linked to zinc deficiency.*  Copper is needed to activate superoxide dismutase (SOD), a major antioxidant enzyme found in the lens.*20 

Herbal Antioxidants

The fruit of Bilberry (Vaccinium myrtillus) contains unique blue/violet bioflavonoids called anthocyanosides. These phytonutrients offer potent antioxidant protection against free-radical damage.*  Bioflavonoids also reduce the activity of aldose reductase,*21  as aldose reductase allows the lens (and retina) to accumulate unhealthy levels of naturally occurring sugars which can cause damage to the retina.*22

In a study of 116 people, both night vision and the ability to see after exposure to glare were maintained after taking 300 mg/day of standardized bilberry extract.*23  These effects were reported in healthy people, suggesting that constituents of bilberry play a functional role in promoting good vision,* though the mechanism is not yet understood.  Standardized bilberry extracts have also been reported to protect the lens from losing its transparency.*24 This protection probably comes from the antioxidant activity of anthocyanosides guarding against free-radical damage to the lens.*

References

1. Leske MC, Sperduto RD. The epidemiology of senile cataracts: A review. Am J Epidemiol 1983;118:152-65.

2. Kahn HA, Liebowitz HM, Ganley JP.  The Framingham eye study; outline and major prevalence. Am J Epidemiol 1977;106:17-32.

3. Seddon JM, Hennekens CH.  Vitamins, minerals, and macular degeneration. Arch Ophthalmol 1994;112:176-9.

4. Jacques PF, Chylack, Jr  LT.  Epidemiologic evidence of a role for the antioxidant vitamins and carotenoids in cataract prevention. Am J Clin Nutr    1991;53:352S-5S.

5. Knekt P, Heliovaara M, Rissanen A, et al.  Serum antioxidant vitamins and risk of cataract. BMJ 1992;305:1392-4.

6. West S, Vitale S, Hallfrisch J.  Are antioxidants or supplements protective for age-related macular degeneration? Arch Ophthalmol 1994;112:222-7.

7. Seddon JM, Ajani UA, Sperduto RD, et al.  Dietary carotenoids, vitamin A, C, and E, and advanced age-related macular degeneration. JAMA 1994;272:1413-20.

8. Hankinson SE, Stampfer MJ, Seddon JM, et al.  Nutrient intake and cataract in women: A prospective study. BMJ 1992;305:335-9.

9. Goldberg J, Flowerdew G, Smith E, et al.  Factors associated with age-related macular degeneration. Am J Epidemiol 1988;128:700-10.

10. Micozzi MS, Beecher GR, Taylor PR, et al.  Carotenoid analyses of selected raw and cooked foods associated with a lower risk for cancer.   J Natl Cancer Inst 1990;821:282-5.

11. Handelman GJ, Dratz EA, Reay CC, van Kuijk FJ.  Carotenoids in the human macula and whole retina. Invest Ophthalmol Vis Sci 1988;29:850- 5.

12. Robertson JM, Donner AP, Trevithick JR.  A possible role for vitamins C and E in cataract prevention. Am J Clin Nutr 1991;53:346S-51S.

13. Jacques PF, Taylor A, Hankinson SE, et al. Long-term vitamin C supplement use and prevalence of early age-related lens opacities. Am J Clin Nutr 1997;66:911-16.

14. Costagliola C, Iuliano G, Menzione M, et al.  Effect of vitamin E on glutathione content in red blood cells, aqueous humor and lens of humans and other species. Exp Eye Res 1986;43:905-14.

15. Leske MC, Chylack LT Jr, He Q, et al. Antioxidant vitamins and nuclear opacities. The Longitudinal Study of Cataract. Ophthalmology 1998;105:831-36.

16. Teikari JM, Rautalahti M, Haukka J, et al. Incidence of cataract operations in Finnish male smokers unaffected by alpha tocopherol or beta carotene supplements. J Epidemiol Community Health 1998;52:468-72.

17. Horwitz J, Dovrat A, Straatsma BR, et al.  Glutathione reductase in human lens epithelium: FAD-induced in vitro activation. Curr Eye Res 1987;6:1249-56.

18. Sperduto RD, Hu TS, Milton RC, et al. The Linxian cataract studies. Two nutrition intervention trials. Arch Ophthalmol 1993;111:1246-53.

19. Anonymous. Zinc chelators and the eye.  Nutr Rev 1982;40:218-20 [review].

20. Harris ED. Copper as a cofactor and regulator of copper, zinc superoxide dismutase. J Nutr 1992;122:636-40.

21. Linuma M, Tanaka T, Mizuno M, et al. Structure-activity correlation of flavonoids for inhibition of bovine lens aldose reductase. Chem Pharm Bull (Tokyo) 1989;37:1813-5.

22. Trevithick JR, Creighton MO, Ross WM, et al.  Modelling cortical cataractogenisis:2. In vitro effects on the lens of agents preventing glucose- and sorbitol-induced cataracts. Can J Ophthalmol 1981;16:32-8.

23. Terrasse J, Moinade S.  Premiers resultats obtenus avec un nouveau facteur vitaminique P “les anthocyanosides” extraits du Vaccinium myrtillus. Presse Med 1964;72:397-400.

24. Bravetti G. Preventive medical treatment of senile cataract with vitamin E and anthocyanosides: clinical evaluation. Ann Ottamol Clin Ocul 1989;115:109.