Dietary carotenoids and age-related macular degeneration

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Health chat with Dr Anthony R Leeds
Title: ‘Dietary carotenoids and age-related macular degeneration’
Prof John Nolan, Nutrition Research Centre Ireland, South-East Technology University, Waterford, Ireland.

Age-related macular degeneration (AMD) is an eye condition that has many causes that result in degeneration of the central part of the retina, leading to impaired central vision. The consequent loss of sight and particularly a reduced capacity for reading impair quality of life and can also lead to social isolation. With an ageing global population the number of people affected is rising and the social and health-care costs will rise too. While prevalence of AMD in South Asia and other Asian countries has been shown to be lower than in European countries (for example early AMD in over 40 year-olds in Asia: 6.8% and in Europeans: 8.8% in one recent survey) it is recognised that prevalence of AMD in South Asia and other Asian countries will rise.

Carotenoids are a large group of naturally occurring coloured pigments in plant foods and some animal foods, some of which are eaten by humans and some accumulate in human tissues where they fulfil important functions. At the back of the eye in the retina three pigments accumulate, these are lutein, zeaxanthin and meso-zeaxanthin. These pigments also accumulate in the brain. These pigments are anti-oxidant (they protect the body from damage by free radical chemicals) anti-inflammatory (they tend to reduce the levels of inflammation, so often an underlying factor in diseases like arterial disease) and in the eye, they absorb blue-light, excess exposure to which can be damaging.

These essential pigments cannot be made in the human body so we are dependant on dietary intake but across much of the world the industrial upscaling of agriculture and horticulture has reduced amounts of these pigments in the food sources. Thus, getting enough from a conventional food diet alone is difficult and needs detailed knowledge.

In this episode John Nolan talks about the work that he and his colleagues have done to investigate the role of carotenoids in macular disease and how to help maintain good function and slow the rate of disease progression in early AMD with supplements of the three carotenoids. John Nolan and his team in Waterford have recently extended their research to investigate the potential for the same supplements in early dementia (to be discussed in episode 4). Professor Nolan and his colleagues believe that AMD should be detected early and ideally prevented from developing by protection of the retina of the eye with carotenoid pigments. More research work is needed but the evidence so far suggests that supplements with carotenoids will have an important role to play in reducing disease progression in AMD and in due course, preventing AMD from developing.

If you or a family member are affected by loss of vision or impaired vision it is important to have a full eye examination as soon as possible with referral for correction of visual acuity problems with glasses and correction of other problems such as cataracts by referral for surgery and treatment of eye infections by skilled health care workers. If eye examination reveals AMD then expert help should be obtained.

Risk factors for AMD include genetic factors, age, sunlight exposure, diet, cardiovascular disease, smoking and alcohol intake. Having a parent or other close relative with AMD means that your risk may well be greater than for others, so you should take more care to address the changeable risk factors: stop smoking, limit alcohol intake, choose a diet with plenty of carotenoid pigments of the right type if possible, and limit exposure to very bright sunlight (wear a hat and if possible use sunglasses) and limit exposure to blue light from electronic screens where possible. If possible, ensure that cardiovascular risks that can affect the eye such as high blood pressure and diabetes are detected and treated.

Good sources of carotenoid pigments in Europe include: Kale, Spinach, Lettuce, Red pepper, Leek and Broccoli. In South Asia good sources of lutein and/or zeazanthin include Bitter gourd, Coriander leaves, Mint leaves, Green chilli, Spinach, Snake Gourd and Drumstick leaves.

Anthony R Leeds 20^th June 2024

Links to useful sources are given below:

Nutrition Research Centre Ireland:

Nutrition Research Centre-Ireland discovers sunlight and diet as key factors for eye health

Pakistan:

Pakistan

Vision

Charity Vision Pakistan

Sight Savers Pakistan

India:

Primary Eye Care Modal In India

Sight Savors India