Preventing Sight Degeneration

Many of us will be aware that eating carrots can help us see in the dark. The beta-carotene contained in carrots can convert into vitamin A which has a critical role to play in night vision. Yet, while this nutritional nugget may well be entrenched in our consciousness, what is less well known is that certain nutrients can help combat the most common causes of deteriorating sight as we age including cataract and a condition known as macular degeneration. Both these conditions are common and represent significant public health problems: macular degeneration is the most common cause of blindness in the ageing population and the incidence of cataracts is set to treble in the next fifty years. The good news is that there is a wealth of research which suggests that increasing our intake of certain foods and nutrients can be very effective in preventing, and in some cases treating, these important conditions.

The very front of the eye is made up of a transparent disc of tissue known as the cornea. Light passes through the cornea and into a lens which sits behind the pupil. The function of the cornea and lens is to focus light on a structure known as the retina at the back of the eye. The retina is the part of the eye which is responsible for vision. At the centre of the retina is a structure called the ‘macula’ which is responsible for the most detailed vision. As we age, the macula can become damaged, giving rise to a condition known as age-related macular degeneration or AMD for short. AMD affects about one in five individuals over the age of 65, and is the most common cause of loss of vision in this age group. Conventional treatment for this condition is centred around the use of laser therapy which can help to control the development of blood vessels in the retina which may be part of the disease.

While the cause of AMD is generally poorly understood, there is good evidence that it is related to damaging, destructive molecules known as ‘free radicals’. More importantly, there are many studies which show that upping our intake of antioxidants (compounds which help neutralise free radicals in the body) may help to prevent or control this condition. The antioxidants which appear to have most impact in this respect are a class of compounds known as the carotenoids. The carotenoids include beta-carotene and its other less well known relatives lutein (pronounced loo”teen) and zeaxanthin (pronounced zee”a”zanthin). The carotenoids are found most abundantly in dark green and orange-yellow vegetables such as carrots, spinach, broccoli and squash. More than one study has found an association between a high consumption of these foods and protection from AMD.

Another foodstuff which appears to reduce risk of AMD is wine. One study published in 1997 found that as little as 2 ” 12 glasses of red or white wine per year might reduce the risk of AMD by up to a half. While it is not known for sure what the protective factor is, wine is known to contain substances called flavonoids that do have antioxidant action in the body. Although minimal wine consumption appears to be beneficial, it is not known whether more is better. However, it does seem likely that the occasional glass of wine might help reduce the risk of AMD in time.

Other nutrients which appear to have a protective role in AMD are vitamin E and zinc. Low levels of both these nutrients has been found in individuals suffering from AMD. Vitamin E is found in vegetable oils, nuts and seeds, egg yolk, and green leafy vegetables, while zinc is found most readily in fish, seafood, meat, eggs and tofu. However, to get useful levels of these nutrients it is sometimes advisable to take a suitable supplement. 400 IU of vitamin E along with 15 ” 30 mg of zinc (balanced with 1 ” 2 mg of copper to prevent copper deficiency) each day are probably useful long-term dosages.

The other major cause of loss of vision associated with ageing is cataract. Cataract is a term used to describe cloudiness in the lens of the eye. Cataracts occur in almost 50 p.c. of people over the age of 75, and one in seven over the age of 55 is affected. Although cataracts and AMD appear to be very different conditions, they have much in common. Like AMD, cataract formation appears to be related to free radical damage. Also, as with AMD, upping antioxidant intake appears to reduce the risk of cataract development.

Two studies published in the American Journal of Clinical Nutrition in 1999 showed that consuming foods rich in carotenoids (especially spinach, kale and brocolli) was associated with a reduced risk of cataract formation. Apart from the carotenoids, two other antioxidant nutrients which appear to help prevent cataracts are vitamins C and E. One study published last year in the Archives of Opthalmology found that individuals taking a multivitamin and mineral supplement containing vitamin C and/or vitamin E in the long term could reduce their cataract risk by 60 p.c. Another study published in the American Journal of Clinical Nutrition in 1997 showed that just vitamin C alone could reduce cataract risk by 70 p.c. if taken for 10 years or more.

Individuals wanting to do what they can to preserve their eyesight as they age might do well to consume a diet rich in the carotenoid containing foods. In addition, it may help to take 400 IU of vitamin E, 500 mg of vitamin C and 15 ” 30 mg of zinc (balanced with 1 ” 2 mg of copper) each day.