Antioxidants against macular degeneration and blindness

Antioxidants put the brakes on the most common reason for blindness in the U.K. It also looks like they can prevent blindness. Other dietary supplements can directly improve sight; if they are taken in time.

The most common cause of blindness in the U.K. is macular degeneration, also known as AMD. AMD is the age related degeneration of the area of the eye (retina) where light is collected, like rays hitting a magnifying glass, causing sharp sight. This degeneration thereby causes blurred sight. Thousands of people in the U.K. are affected by AMD each year. Many more suffer from other forms of poor sight.

The more mild forms of AMD are quite common. With these forms, sight is reduces to such a small degree that the loss is normally not noticed. Optometrists can ascertain such mild forms of AMD with the finding of small yellow spots on the retina under an eye exam. These defects are composed of accumulated waste products. Almost everyone over the age of 50 has at least one such defect. Small defects are unimportant, even when there are many. But, if they are larger there is a risk of serious AMD. About 30% of those with larger defects will have advanced AMD within five years.

Therefore it created a sensation when, in 2001, an American study showed that this five year risk could be reduced to 20%, meaning by a third, with the supplement of zinc and antioxidants. The doses given in the study were: 500 mg vitamin C, 400 units vitamin E, 15 micrograms beta-carotene as wall as no less than 80 mg zinc per day. Treatment with antioxidants alone appeared to be just as effective, but could not be proven statistically.

But how does one know if one has the early stages of AMD? Because the loss of sight in such cases is minimal, one might not go to an eye doctor. Therefore it is recommended that everyone over the age of 55 undergo an eye exam so they can consider whether or not they should take supplements. Because beta-carotene has been reported to cause lung cancer in smokers, this advice is only relevant to non-smokers.

Antioxidants can also inhibit the development of AMD, but this use is not often considered. The question however remains whether antioxidants can prevent AMD from occurring in the first place. A new Dutch study implies that they can.

Sharper sight
In this study 6,000 residents of Rotterdam were followed starting from the years 1990-93. In 2004 560 of them had AMD, but it was not entirely random who developed AMD. Both a high intake of zinc and vitamin E lowered the risk, but only a little. If one received high doses of both vitamins C and E, beta-carotene and zinc, the risk of developing AMD was reduced an impressive 35%.

An Italian randomised study published last year showed even more intriguing results. In this study 106 patients with an early form of AMD were treated over the course of a few years with a combination of fish oil (n-3 fatty acids), the antioxidant Q10, as well as the dietary supplement, carnitine. The goal was to improve the fatty acid metabolism of the retina. Carnitine advanced the metabolizing of fat such that the depositing of waste products was counteracted. This is important in the retina seeing that the concentration of n-3 fatty acids is even richer than in brain tissue. 30% of the matter in the retina is composed of n-3 fatty acids as opposed to 20 % in the brain.

The result, with regards to light sensitivity in centre of the eye, visual acuity (measured with a normal eye chart), and perceptual changes in the retina, was not only the progress of the disease was stopped, but that there was also a direct improvement! The area of the eye where defects could be seen was not just unchanged, but had shrunken! All of this was statistically sound.

With advanced AMD one is both blind and can see. One cannot read, watch TV, or recognize faces. But peripheral vision is retained. One can see out of the corner of the eye, so it is still possible to orientate oneself in space and walk, with care. This functional blindness can, in many cases, be improved by antioxidants and, according to the above mentioned research; the condition can even be improved by simple dietary supplements, if they are taken in time.


References:

  1. Age-Related Eye Disease Study Research Group.Arch Ophthalmol. 2001 Oct;119(10):1417-36. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8.
  2. Feher J et al. Ophthalmologica. 2005 May-Jun;219(3):154-66.Improvement of visual functions and fundus alterations in early age-related macular degeneration treated with a combination of acetyl-L-carnitine, n-3 fatty acids, and coenzyme Q10.
  3. van Leeuwen R et al. JAMA. 2005 Dec 28;294(24):3101-7. Dietary intake of antioxidants and risk of age-related macular degeneration.