New clinical trials show conclusively that dietary antioxidants help to stop the progression of macular degeneration.

Macular degeneration, also known as age related macular degeneration (AMD) is a disease of the macula of the eye that is found predominantly in elderly people and is the leading cause of central vision loss in the USA for those over the age of 50 years.

The macula is the central area of the retina of the eye that, if diseased or damaged, results in the inability to read or see fine detail. There are two main types of advanced AMD - dry and wet. The former makes up over 90% of cases and, the less common wet form makes up the remaining 10%.

The cause of dry macular degeneration is the formation of deposits called drusen on the macula. Drusen are fairly common in individuals over 50 years of age and do not cause any visual impairment when found in small numbers. However, when they become larger and more extensive they do start to make an impact on vision.

Drusen are yellowish accretions of lipoproteins in the lining of the retina. The cause of AMD and reason that drusen form is not entirely clear but there is a connection with cholesterol deposits in arteries and other parts of the body.

There are a number of important risk factors for AMD:

1. Oxidative stress: This state is associated with free radical overload and antioxidant deficiency that occurs more frequently with aging. There is convincing evidence that oxidative stress is the underlying cause of AMD as oxidative stress increases with age and is associated with several diseases like diabetes, obesity and others.
2. Inflammation: An inflammatory process is also involved in the formation of drusen and both the dry and wet types of AMD.
3. Age: The older you are the greater your risk of developing AMD.
4. Smoking: Smokers have a higher incidence of AMD.
5. Genetic predisposition: Certain genes have been identified that place some people at increased risk for AMD.
6. Obesity: This is associated with oxidative stress and increased risk for AMD.
7. High blood pressure and high cholesterol levels: Individuals with hypertension and abnormal blood lipid levels have an increased risk for AMD.  

Prevention of AMD with antioxidants

Several very large studies have shown conclusively that those individuals who eat a diet rich in antioxidants have a lower risk of developing AMD. Two of the most comprehensive of these are the Age Related Eye Disease Study and the Blue Mountains Eye Study both of which monitored the diets and examined the eyes of over 3500 participants for at least eight years.

These two studies confirmed earlier research that showed how antioxidant vitamins can slow the progression of AMD by up to 35%!

However there were a few important findings that should be noted.
Although these and other studies have provided conclusive evidence that a diet high in antioxidants can protect against the development of macular degeneration, the Blue Mountains Eye Study found that an intake of the antioxidant, ß-carotene in high doses actually increased the risk of developing AMD. High doses of ß-carotene have also been shown to increase the risk of cancer in smokers.

Another study conducted by the Massachusetts Eye and Ear Infirmary showed that those who ate significant quantities of foods that  were rich in antioxidants were protected against both wet and dry forms of AMD; even though they did not take antioxidant vitamin supplements.

Taken together these studies make two important points. The first is that we need a regular, intake of safe, effective antioxidants to help prevent the onset and/or progression of AMD. Secondly, that it is better to take the antioxidants in their natural form rather than high doses of individual antioxidants (like ß-carotene) that may have harmful side effects.

In this respect it is worth noting that spices have the highest antioxidant activity of all food groups (American Journal of Clinical Nutrition 2006). They are the best source of the wide variety of antioxidant compounds that are necessary to help counter the effects of aging and age-related diseases like AMD that are associated with free radical damage and oxidative stress. Spices also provide a number of natural anti-inflammatory compounds that help to control the inflammatory processes that underlie degenerative conditions like AMD.

Rather than waiting until we develop AMD or any of the other degenerative diseases associated with aging, we should increase out consumption of spices to ensure that we provide ourselves with the safest, most effective antioxidant protection. 

References:

1. Dietary Antioxidants and the Long-term Incidence of Age-Related Macular Degeneration The Blue Mountains Eye Study.
   Ophthalmology. 2007 Jul 28; [Epub ahead of print]Click here to read Links
   Tan JS, Wang JJ, Flood V, Rochtchina E, Smith W, Mitchell P.
   Department of Ophthalmology, Centre for Vision Research, Westmead Millennium Institute, Westmead Hospital, University of Sydney, Sydney, Australia.
2. Dietary intake of antioxidants and risk of age-related macular degeneration.
   JAMA. 2005 Dec 28;294(24):3101-7.Click here to read Links
    van Leeuwen R, Boekhoorn S, Vingerling JR, Witteman JC, Klaver CC, Hofman A, de Jong PT.
   
3. 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
   Arch Ophthalmol. 2001 Oct;119(10):1417-36.Click here to read Click here to read Links
   Age-Related Eye Disease Study Research Group.
   
4. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group.
   JAMA. 1994 Nov 9;272(18):1413-20.
   Seddon JM, Ajani UA, Sperduto RD, Hiller R, Blair N, Burton TC, Farber MD, Gragoudas ES, Haller J, Miller DT, et al.
   Epidemiology Unit, Massachusetts Eye and Ear Infirmary, Boston 02114.