AMD research: A theory that eating certain fruit and vegetables can help prevent serious eye disease is being tested in a new study at Queen's University in Belfast. The research follows on from a study in the United States in 2001 which found that certain compounds that occur naturally in fruit and vegetables slowed down the progression of age-related macular degeneration (AMD).
The disease, which results in a gradual blurring of central vision, is one of the leading causes of blindness in the elderly and up to 25 million people are affected worldwide. Smoking is known to be one of the main risk factors associated with the disease.
Dr Jayne Woodside of the Department of Medicine at Queen's said research into the possibility that nutrition could help prevent AMD was in the early stages. The study she is leading in Belfast will build on knowledge gained from the US study, which was carried out on people who were already in the early stage of the disease. That study found that vitamins C, E, b-carotene and zinc significantly reduced the risk of the disease developing into later stage AMD.
The Belfast study is using 150 healthy volunteers and will test for the effect of giving different compounds than those administered in the US study. For half of the test period, participants will be given b-carotene - as in the US study - but they will also be given two other carotenoids called lutein and zeaxanthin, which as well as being found in fruit and vegetables, are also found in the retina of the eye. Dr Woodside said it was possible that taking these particular carotenoids could have an even more beneficial effect than the compounds given in the US study and it was important to establish this.
She said another novel feature of the Queen's study was that it would compare the effect of taking the carotenoids as they naturally occur in food or when taken as food supplements. For an initial eight weeks, participants are given spinach powder or carrot juice, and during a later eight-week period they are given food supplements.
"It may be that when you extract the pure compound for a food supplement it may not have the same effect as it does as a food," Dr Woodside said.
The effect of taking the carotenoids is expected to result over the eight-week test period in a greater macular pigment density at the back of the eye and this protects against the risk of macular degeneration.
The final results of the study are expected next year and while Dr Woodside said there was no hard evidence as yet for the benefits of the specific compounds, people should follow the general advice to eat at least five portions of fruit or vegetables a day.