Nutrients for macular degeneration: Anti-oxidants

[08/06/2012]

Nutrients for macular degeneration: Anti-oxidants

Age related macular degeneration (AMD) is the leading cause of blindness in developed nations; I had previously blogged about the treatment of wet AMD and the controversy surrounding the different treatment options. A lot of research has been carried out to identify the cause and possible risk factors for AMD and as with many other diseases, the development of AMD is a consequence of the interplay between genetic and environmental factors.

There is of course little we can do to alter our genetic makeup(for now) but the identification of different genes associated with this disease only allows further development of therapeutic options in the future. Environmental influences such as smoking and diet have also been strongly linked with AMD and unlike our genes, we can directly impact on the disease by changing our behavior or habits.

The identification of specific nutrients which maybe beneficial for AMD came from the Age Related Eye Diseases Study (AREDS). From this study, the importance of anti-oxidants and zinc in preventing the progression of AMD was discovered.

What are anti-oxidants?

To understand how anti-oxidants are beneficial, one must first understand how our body works. Our body's cells are constantly at work and particularly in our eyes (where the photo transduction process which converts light into electrical impulses uses large amounts of energy), a lot of free radicals are generated. These free radicals are reactive oxygen particles and can be damaging to our cells. What anti-oxidants do are in effect to 'neutralize' these oxygen particles and prevent further damage.

Anti-oxidants which were found to be beneficial for AMD were Vitamins A (beta-carotene),C and E and zinc. The study showed beneficial effects of these anti-oxidants only in individuals at high risk of developing advanced AMD - there was a risk reduction of 25% in these individuals. In people with no AMD or early AMD however, there was no apparent benefit.

The AREDS formulation

As a result of the findings of this study, there have been a flood of these 'eye supplements' into the market since 2001. The formulation used in the study was 500mg of Vitamin C, 400 IU of Vitamin E, 15 mg of beta-carotene, 80mg of zinc and 2 mg of copper (copper was added to prevent copper deficiency which could be associated with high doses of zinc supplementation). With aggressive marketing from the pharmaceutical companies, many consumers have started using these supplements 'to protect their eyes'!

I've been asked by many of my patients about taking different varieties of supplements and my advice to them is always to look at the evidence. As a doctor, I can only base my recommendations on scientific evidence and strong scientific evidence can only be achieved by doing very large controlled trials. There are always claims by companies selling these supplements about the "proven" effects of their product but I would always take all results with a pinch of salt. Without sounding too cynical, information from Google should also be filtered through carefully. Even the scientific journals which I read can sometimes be misleading - it is therefore important that we be cautious about information we read or hear about.

As for the AREDS formulation, it is indeed an important addition to our armamentarium for the battle against AMD but we must be mindful that it is currently proven to be beneficial only to people at high risk of developing advanced AMD (i.e. one eye with severe AMD or both eyes with many medium-sized or large yellowish deposits in their macula called drusen). Moreover, smokers who take the AREDS formulation may be at increased risk of lung cancer due to the interaction with beta-carotene so my advice would be to discuss with your physician before 'popping more pills'.

Other nutrients?

You may have read about other substances with potential benefits to the eye such as lutein or zeaxanthin and omega fatty acids. There is currently an ongoing AREDS 2 study which will investigate the impact of these other supplements on AMD and more definite information will be available in the next 1 to 2 years.I shall blog more about lutein and zeaxanthin and omega fatty acids in subsequent posts.