Animal studies also show that deficiencies of vitamins A or E may be associated with degeneration of the retina
or disruption of photoreceptors (Invest Ophthalmol Vis Sci, 1979; 18: 683-90; Invest Ophthalmol 1974; 13: 499-510). Vitamin C has also been shown to protect against the ageing effects of ultra-violet light in an animal study (Invest Ophthalmol Vis Sci, 1985; 26: 1589-98). (Remember, though, that animal studies don't necessarily apply to humans, which is why WDDTY is against animal testing for this purpose.)
Zinc is the most important mineral for sufferers of AMD, as concentrations of zinc are higher in the retina than in any other organ. According to WDDTY panel member Dr Melvyn Werbach, author of the sourcebook Nutritional Influences on Illness (Tarzana, CA: Third Line Press, 1996), zinc deficiency in the retina may reduce the activity of catalase, an enzyme found in the tissues of the macula.
Reduced activity of this enzyme is associated with AMD (J Am Coll Nutr, 1991; 10: 536). Low levels of zinc in the retina may also interfere with the body's utilisation of vitamin A (J Nutr, 1975; 105: 1486-90).
In one double blind study of 151 patients, those given zinc suffered significantly less loss of visual acuity than those given a placebo after one or two years (Arch Ophthalmol, 1988; 106: 192-8).
Besides zinc, copper is also vital to the retina; however, in this condition, copper levels are often elevated, which can prove toxic to the macula (India J Ophthalmol, 1981; 29: 351-3). Taking the Pill or HRT can cause abnormally high copper levels in women (Stephen Davies, Nutritional Medicine, Pan, 1987). High levels of copper can also affect the levels of zinc in your body, and elevated blood levels of either mineral are linked with AMD (Ann Ophthalmol, 1985; 17: 419-22). So, if you're on or have been on HRT, you might wish to get your copper levels checked.
One final important nutrient is the amino acid taurine, which is necessary for normal vision and lost when you are exposed to bright light. Studies have shown that a deficiency of taurine can bring on degeneration of the retina (Science, 1975; 188: 949-51).
There's no doubt that taking certain vitamins and minerals can even help slow or reverse the disease in those who have already developed the condition.
In one small study of 20 patients, 90 per cent improved after receiving vitamin E and replacing table salt with sea salt, which is rich in natural minerals. One fifth of the patients, who had only able to make out hand movements, enjoyed such improvements in vision that they were able to read newspapers again. These improvements carried on only so long as they took the supplements, suggesting that people with AMD may have higher requirements for antioxidants and certain minerals (Todd GP, Nutrition, Health & Disease, Norfolk, Virginia: The Donning Company, 1988).
The best results occur when patients are given a combination of the nutrients known to be vital to a well functioning retina. In one study, patients' vision improved when they were given a supplement of vitamins C and E, copper, manganese, selenium, beta carotene (a precursor of vitamin A) and riboflavin (vitamin B2) (J Am Coll Nutr, 1991; 10: 550). In another study, progression of the disease was slowed down with vitamins A, C and E plus selenium, with the best results among those where treatment was started early (Prevention, March 1985: 74-80).