A Diet Rich In Fatty Fish Is Beneficial In Reducing Progress Of Eye Disease

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Main Category: Eye Health / Blindness
Also Included In: Nutrition / Diet
Article Date: 11 Jun 2009 - 0:00 PDT

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A study published ahead of print in the British Journal of Ophthalmology suggests that in order to diminish the development of the age related eye disease called macular degeneration, a weekly consumption of two to three portions of fatty fish could be beneficial.

The researchers support their conclusions based on a long eight year study of 3,000 patients. They were all taking part in a supplements trial called the Age Related Eye Disease Trial, on which they were all monitored for the possible development of macular degeneration.

Age related macular degeneration, also called AMD is becoming more common over the years as the proportion of the elderly population worldwide increases. AMD is an illness that progressively degenerates the back of the eye (macula). It deprives older aged people of the ability to perceive fine detail, and eventually blinding them.

The patients participating in the study were arbitrarily allocated to receive one of the following on a daily basis.
• A dummy pill (placebo).
• Antioxidants of vitamins C (500mg), E (400 IU), and beta carotene (15 mg).
• Zinc (80 mg) and copper (2 mg) minerals.
• The antioxidants above plus zinc mineral.

The trial results suggested that taking antioxidants plus minerals limited the development of late stage AMD, but not on the early stages of the disease.

On occasions, participants received a general physical and eye examination, and with help of a validated food frequency questionnaire, they were also quizzed about their diets. As well, thorough photographs of the macula were taken at the start of the study, two years later, and then again every year.

The results concluded that evolution to both dry and wet forms of advanced disease was 25 percent less likely among those participants consuming a diet rich in omega 3 fatty acids (docasahexenoic (DHA) and eicosapentaenoic (EPA) acids).

This finding held true whether or not the participants were taking supplements. But if participants took a combination of supplements with combined with a high intake of DHA, it seemed to act negatively in halting the progress of early stage disease. Participants who consumed daily the antioxidant vitamins and zinc, and also ate 2.2 mg or more of beta carotene daily, were astonishingly 50 percent more likely to progress to the advanced disease stage.

A diet rich in omega 3 in this study equated to 64 mg a day or more of DHA and 42.3 mg a day of EPA. This is considered much lower than the suggested combined total daily intake of 650 mg a day.

Test results also conclude that it is very beneficial to have a diet rich in low glycaemic index (GI) foods, such as whole grain bread for example.

The authors continue by explaining that if people substitute five slices of whole grain bread instead of white bread out of a total intake of 250 g of carbohydrates, this could result in a reduction of about 8 percent of advanced age related macular degeneration over five years.

GI measures how fast carbohydrates are converted into sugars in the intestine and enter the blood.

Consuming a mixture of high omega 3 with a low GI carbohydrate intake can diminish the risk of progression to the advanced disease stage even more, cutting it by 50 percent.

The authors conclude that in order to reduce the risk of both early and late stage of AMD, the daily intake of omega 3 can be achieved by eating two to three servings of fatty fish, such as salmon, tuna, mackerel, shellfish, and herring every week.

"Does eating particular diets alter the risk of age-related macular degeneration in users of the Age-Related Eye Disease Study supplements?"
C-J Chiu, R Klein, R C Milton, G Gensler, A Taylor
doi:10.1136/bjo.2008.143412
Br J Ophthalmol

Written by Stephanie Brunner (B.A.)
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