Health

  • Written by Clare Collins, Professor in Nutrition and Dietetics, University of Newcastle
imageThere's evidence vitamins can slow the progression of existing macular degeneration. from www.shutterstock.com

Vitamin and mineral supplements won’t prevent the development of age-related macular degeneration. But there is some evidence taking supplements containing vitamin C, vitamin E and zinc may slow the progression of age-related macular degeneration in those who already have it. This evidence comes from two major systematic reviews published this year, conducted by the Cochrane collaboration.


Read more - Explainer: what is age-related macular degeneration?


The reason researchers thought about testing dietary supplements for eye disease relates to how the eyes convert light into sight. Light gets absorbed into pigments in the retina at the back of the eye. This process produces byproducts called free radicals. Free radicals are oxygen atoms that have unpaired electrons, which makes them highly reactive and unstable. As these atoms hunt around to find another electron so they can become more stable, they trigger damage to other molecules, the walls of cells and to DNA. In the eyes, this contributes to gradual loss of vision.

Anti-oxidants are nutrients that absorb free radicals and include vitamin A, C and E, the minerals zinc and selenium, and many phytonutrients found in edible plants including vegetables and fruit. Theoretically if more anti-oxidant nutrients were present in the eye, less damage should be done to the eye. Lets look at what the scientific evidence says.

The first review looked at people who already had age-related macular degeneration and includes research published up until March 2017. They found 19 trials in adults who already had early or moderate macular degeneration. Nine studies compared people taking vitamin supplements to those either not taking them or being given a placebo (dummy) capsule for periods of time from nine months to six years.

They found the vitamin supplements were associated with 28% lower odds of progressing to late stage macular degeneration. The studies that compared zinc supplements to a placebo found a 17% lower risk of progressing to late stage macular degeneration.

The authors final conclusion cautiously suggested use of antioxidant vitamin and mineral supplements may help delay disease progression in people with existing age-related macular degeneration, with a reminder that while vitamin supplements are generally safe they can have harmful effects in some, such as smokers.


Read more - Monday’s medical myth: take a vitamin a day for better health


The second review looked at prevention of age-related macular degeneration. There were four trials that compared taking Vitamin E to a placebo which found vitamin E had no effect on prevention of age-related macular degeneration. And one trial found a side-effect of an increase in risk of haemorrhagic stroke in those taking vitamin E.

Two studies used beta-carotene (an organic compound found in plants that the body converts into Vitamin A) and found no reduction in risk of new onset macular degeneration with one study confirming an increased risk of lung cancer in the smokers.

One study in men compared vitamin C or multivitamins with a placebo and found no effect for vitamin C and a slightly higher risk for age-related macular degeneration in the group taking the multivitamins. There was no evidence related to other antioxidants such as lutein or zeaxanthin.

Loss of vision due to age-related macular degeneration is associated with a loss of ability to do the things that help to improve your nutrition related health and well-being as you age. Compared to adults of a similar age and sex who did not have age-related macular degeneration, those with it have a higher risk of death from heart disease and all other causes.

It’s wise to trying and boost your diet quality for a host of reasons, by eating more healthily as you age and trying to quit smoking. You can use our free Healthy Eating Quiz to check your score.

Meanwhile, try to increase you intake of foods rich in phytonutrients. Oysters, meat, eggs, seafood, nuts, tofu, legumes, wheat germ and wholegrain foods contain zinc. Oranges, mandarins, lemons, limes, strawberries, kiwifruits, tomato, capsicum, spinach, broccoli, cabbage and green vegetables contain vitamin C. Nuts, seeds, wheatgerm and eggs contain vitamin E. Egg yolk, corn, spinach, pumpkin, cucumber, kiwifruit, red grapes, zucchini, capsicum, oranges and mangoes contain the antioxidants lutein and zeaxanthin.

If you’ve been told you have age-related macular degeneration then you should discuss the risks and benefits of supplementation with your doctor. Keep in mind vitamin supplements that include beta-carotene are not recommended if you are a smoker. Remember to talk to your GP about your eye health as you age.

Disclosure

Clare Collins is affiliated with the Priority Research Centre for Physical Activity and Nutrition, the University of Newcastle, NSW. She is an NHMRC Senior Research and Gladys M Brawn Research Fellow. She has received research grants from NHMRC, ARC, Hunter Medical Research Institute, Meat and Livestock Australia, Diabetes Australia, Heart Foundation. She has consulted to SHINE Australia, Novo Nordisk, Quality Bakers and the Sax Institute. She was a team member conducting the systematic reviews to inform the 2013 revision of the Australian Dietary Guidelines and the 2017 evidence review on dietary patterns and heart disease for the Heart Foundation.

Authors: Clare Collins, Professor in Nutrition and Dietetics, University of Newcastle

Read more http://theconversation.com/do-vitamin-supplements-prevent-macular-degeneration-86519

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