Can oily fish prevent eye disease?

Eating food rich in omega-3, such as oily fish like mackerel and sardines, could help cut the risk of developing age-related macular degeneration (AMD), recent media reports suggest.

Mackerel
Mackerel

Participants who ate the most omega-3 rich foods were 38 per cent less likely to develop AMD than those eating the least.

Eating just two portions of oily fish a week was enough to help protect against AMD.

Previous studies have already linked omega-3 fatty acids with a variety of health benefits.

Latest NICE lipid modification guidance advises people at risk of, or with cardiovascular disease (CVD) to eat at least one portion of oily fish a week.

What is the research?
The Australian research team conducted an online search for papers published between 1984 and 1996 that evaluated fish consumption and overall omega-3 intake for the prevention of AMD. In all, nine studies were identified involving 88,974 participants, aged 43 to 84.

Participants were asked to record their weekly food intake and medical records were analysed for cases of AMD.

Mean follow-up time for the studies ranged from five to 12 years during which 1,847 participants developed early stage AMD and 1,356 developed late stage AMD.

The researchers performed a meta-analysis of all the studies to produce a single result, which would show what effect omega-3 fatty acids or oily fish have on early or late AMD. They found those who consumed foods rich in omega-3 on a weekly basis were 38 per cent less likely to develop AMD than those who did not eat any omega-3 foods.

Participants who consumed oily fish twice or more per week were 24 per cent less likely to develop early AMD and 23 per cent less likely to develop late AMD than those who consumed no oily fish.

What do the researchers say?
Lead researcher Dr Elaine Chong, from the department of ophthalmology at the University of Melbourne, said: 'Omega-3 fatty acids, docosahexanoic acid (DHA) in particular, form an integral part of the neural retina.

'Outer cells of the retina are continually shed and regenerated, and deficiencies of omega-3 may therefore initiate AMD.

'A diet rich in omega-3 and fish, as a proxy for omega-3 intake, could therefore prevent AMD,' she said.

However, there is insufficient evidence from the current literature to support their routine consumption for AMD prevention, added Dr Chong.

People who consume high levels of omega-3 are also likely to be consuming high levels of antioxidants which have also been associated with reducing AMD. This makes it unclear whether it is the high levels of omega-3 or the antioxidants, or a combination of both that lowers AMD risk, warn the researchers.

What do other researchers say?
Barbara McLaughlan, campaigns manager at the Royal National Institute for the Blind, called for randomised controlled trials to examine further whether omega-3 and fish consumption could help in preventing AMD.

'At the moment the evidence base is just not strong enough to recommend eating oily fish to prevent AMD. GPs should advise patients to stop smoking as that is the only proven avoidable risk factor for AMD.

'In the interim we would encourage the DoH to do more to raise awareness of the link between smoking and blindness, which we believe presents a powerful incentive for people to stop smoking.'

Informing Patients
  • Eating food rich in omega-3 could lower the risk of developing AMD by 38 per cent.
  • Randomised controlled trials are needed to fully investigate the effects of omega-3 on AMD.
  • GPs should advise patients to quit smoking as that is the only proven avoidable risk factor for AMD.

sanjay.tanday@haymarket.com

Arch Ophthalmol 2008

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