By Sridhar Nadamuni
If you want to keep eye disease at bay, there is nothing better than fish: Two to three portions of fatty fish eaten weekly could help prevent worsening of the age related eye disease, macular degeneration, according to research published online in the British Journal of Ophthalmology on June 9, 2009.
In the Age Related Eye Disease Study, Dr Chung-Jung Chiu, of the Laboratory for Nutrition and Vision Research, at Tufts University, Boston, Massachusetts, USA, and colleagues monitored almost 3,000 participants on a nutritional intervention for the development of age-related macular degeneration over eight years.
Age related macular degeneration, or AMD, a progressive degenerative condition, is a ‘devil in detail’ affecting the back of the eye (macula). With increasing age, the disease can lead to blindness eventually.
The researchers allocated the study participants randomly to receive either a daily dummy pill (placebo); or antioxidants of vitamins C (500 mg), E (400 IU), and beta carotene (15 mg); or the minerals zinc (80 mg) and copper (2 mg); or the antioxidants plus zinc.
Based on the trial results, the researchers suggest that taking antioxidants along with minerals curbed progression of late stage, but not early stage disease.
The participants’ dietary habits were assessed using a validated food frequency questionnaire and regular general physical and eye exams as well as detailed photographs of the macula, taken at the start of the study, after two years and then again annually.
The researchers found that the progression to both dry and wet forms of advanced disease was 25% less likely among those eating a diet rich in omega 3 fatty acids (docasahexenoic (DHA) and eicosapentaenoic (EPA) acids), regardless of the participants taking supplements. However, a combination of supplements and a high intake of DHA may not halt the progress of early stage disease.
A diet rich in omega 3 in this study (64 mg/day or more of DHA and 42.3 mg/day of EPA) is much lower than the recommended combined total daily intake of 650 mg/day.
But then, the combined intake of all the antioxidant vitamins plus zinc, as well as 2.2 mg or more of beta carotene daily led to more likelihood (50% more) to progress to advanced disease.
A diet rich in low glycaemic index (GI, a measure of how fast carbohydrates are converted into sugars in the intestine and enter the blood) foods, such as wholegrain bread, five slices daily might reduce almost 8% of advanced age related macular degeneration over five years. A diet of high omega 3 and low GI carbohydrate intake reduced the risk of progression to advanced disease by 50%.
The authors advise eating two to three servings of fatty fish, such as salmon, tuna, mackerel, shellfish, and herring every week, to achieve the recommended daily intake of omega 3, substantially cutting the risk of both early and late stage AMD.
