Low-GI diet linked with reduced risk of most common cause of loss of vision in adults

Age-related macular degeneration (AMD) is the most common cause of visual deterioration and blindness in adults. It involves damage to the mucula ” the part of the retina at the back of the eye responsible for acute vision. One of the underlying processes which is thought to promote AMD is the action of damaging molecules known as ‘free radicals’. Below, I have pasted in an article which explores this process and some nutritional strategies that may combat it in more depth.

Another key process that may give rise to AMD is glycation – basically damaged caused by the reaction of glucose with bodily tissues. Glycation can damage tissues in the eyes, including the retina. Glycation compounds are also known to build up in what are known as ‘drusen’ – white or yellow spots that are typically found in individuals with AMD or those at risk of AMD.

Because glycation is a process involving glucose, one might expect that eating foods that liberate sugar relatively quickly into the bloodstream (high glycaemic index foods) might accelerate this biochemical process, and the consequences (including AMD) of it.

In a study published recently in the American Journal of Clinical Nutrition, the relationship between the overall glycaemic index (GI) of the diet and risk of AMD was assessed in more than 4000 men and women. For those consuming diets with the highest GI, compared to those with the lowest GI diets, risk of suffering from large drusen was up 42 per cent. The study also showed that higher GI diets were associated with increased severity of AMD. The authors of this study concluded that eating a lower GI diet would eliminate 20 per cent of AMD cases.

Not only will high GI foods enhance glycation, but they also seem to enhance the free radical damage (known as ‘oxidative stress’) that may also be a factor in the condition. High GI foods may also encourage inflammation in the body, another process that might enhance risk of AMD.

References:

Chiu C-J, et al. Association between dietary glycemic index and age-related macular degeneration in nondiabetic participants in the Age-Related Eye Disease Study. Am J Clin Nutr 2007 86: 180-188.

Natural Approaches to Combating Macular Degeneration – 24th February 2002

I was never very interested in food as a child, but I do remember being encouraged to eat plenty of carrots to help me see in the dark. Not all nutritional folklore is supported by sound science, but this one is: carrots are loaded with the nutrient beta-carotene, and the vitamin A this may convert to in the body is indeed important for night vision. In recent years, however, science has begun to examine more closely the link between diet and eyesight. In particular, researchers have been busy identifying the true causes of deteriorating eyesight, in an attempt to discover ways of protecting against eye disease. It turns out that the humble carrot, in addition to helping with night sight, has other ocular benefits up its sleeve. The latest research suggests that consuming carrots and other deeply coloured vegetables may do much to preserve our visual powers as we age.

Much of the scientific community’s recent research into the links between diet and eye health has focused on a condition known as macular degeneration. The macula is part of the retina; the structure at the back of the eye that essentially fulfils the same function as film in a camera. The macula ‘sees’ whatever our eye is focusing on, and is responsible for our most detailed and intricate vision. However, just like all the other parts of our body, the macula can be subject to the vagaries of time. Damage to the macular as we age can give rise to a condition known as age-related macular degeneration (AMD). AMD tends to be one of those conditions you don’t hear about until you have it. Yet, despite its relative obscurity, it is actually the most common cause of visual deterioration and blindness in the developed world.

For a long time, AMD has been viewed as a natural part of the ageing process, and a condition about which we could do very little. However, a better understanding of what actually causes AMD has thrown up some very promising possibilities for its treatment and prevention. In recent years, scientists have discovered that AMD is related to molecules known as free radicals. Free radicals are natural by-products of the biochemical and physiological processes that keep us alive. Essentially waste products, free radicals are believed to be the major players in the damage characteristic of AMD. However, these rogue molecules don’t get it all their own way in the body. The effects of free radicals are tempered by substances known as antioxidants, many of which are nutrients. The good news is that upping our intake of antioxidants appears to help protect against AMD.

The antioxidants that appear to offer most potential in this respect are a class of compounds known as the carotenoids. The most famous of the carotenoids is beta-carotene. However, its relatives lutein (pronounced loo”teen) and zeaxanthin (pronounced zee”a”zanthin) also seem protect the eyes from free radical attack. Carotenoids are found in dark green and orange-yellow vegetables such as spinach, broccoli, squash, and of course, carrots. Not surprisingly, more than one study has found that high levels of carotenoids in the system appear to protect against AMD. It appears that eating plenty of carrots and other carotenoid-rich veggies is a worthwhile insurance policy against visual problems later in life.

Our diet offers more potential for the preservation of our eyesight in the form of wine. One study published 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 very moderate wine consumption appears to be beneficial, it is not known whether more is better. Nevertheless, it does seem likely that the occasional glass of wine has benefits for our eyes.

While the right diet might offer real potential for protecting against AMD, I generally recommend a more aggressive approach for individuals who already have signs of this condition. Supplements of eye supporting nutrients may provide benefits in addition to those provided by dietary change. In fact, a study published last year found that the taking of a supplement containing beta-carotene and other antioxidants (vitamins C and E) significantly reduce the risk of severe AMD in those at high risk of this condition.

4 Responses to Low-GI diet linked with reduced risk of most common cause of loss of vision in adults

  1. Audrey 2 August 2007 at 9:07 am #

    When I was studying herbal medicine, I was given a hand-out on Vaccinium myrtillus (bilberries, whinberries). Naturally, I can’t find it now. It had all the research, up to that time, on the benefits of bilberries for the prevention or halting the deterioration of AMD. I love whinberry pie, but maybe that doesn’t fit in with a GI diet and it is a very rare treat. It is more practical to eat blueberries, but they don’t have the wow factor. You can get a tincture from medical herbalists. That tastes delicious.
    Audrey

  2. helen 5 August 2007 at 11:35 pm #

    well sugar strikes again ! there is even a suggestion that sugar could be responsible for myopia as it causes pressure in the eyeball & causes it to change shape. Sorry I don’t have a link nor can I remember the name of the research paper to give you.

  3. Barry Wheeler 14 April 2008 at 3:10 am #

    There is a study now, the AREDS study I think, that is investigating the relationship between antioxidants and AMD. There appears to be a lot of evidence indicating the benefits of antioxidants in combating age related macular degeneration.

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