News You Can Use: July 2009
Benefits depend on the stage of disease and whether antioxidant supplements are taken—more studies needed.
Eating fatty fish such as salmon, tuna or mackerel two to three times per week can slow the progression of age-related macular degeneration (AMD) according to a new study published in the British Journal of Ophthalmology.
This research further confirms earlier studies that suggested eating fish can help reduce the risk of getting AMD and demonstrates that some of those already affected by the disease can benefit as well.
“The Tufts University investigator in Boston conducted analyses on
AREDS, a study of 3,000 participants performed in 11 other clinical centers in
the US. The subjects were randomly assigned to receive one of four dietary
supplement(s): 1) placebo;
2) antioxidants of vitamin C, E, and beta
carotene; 3) zinc and copper; or 4) antioxidants (C, E, beta carotene) plus zinc
and followed for a median of 6.5 years for the trial with additional years of
follow-up.”
As part of the study, patients were also asked to fill out food questionnaires and were asked about their diets.
The results concluded that progression to both early and advanced AMD was 25 percent less likely among those participants with a diet rich in omega 3 fatty acids (docasahexenoic (DHA) and eicosapentaenoic (EPA) acids). Fatty fish such as salmon, mackerel, tuna, sardines, and shellfish contain high levels of these fatty acids.
These results were consistent regardless of whether or not the participants were taking supplements. But if participants took a combination of supplements with a high intake of DHA, it seemed to act negatively in halting the progress of early stage disease. Participants who consumed the antioxidant vitamins and zinc daily, and also ate 2.2 mg or more of beta carotene, were surprisingly 50 percent more likely to progress to the advanced disease stage.
“These are very promising and interesting data that confirms previous reports both from AREDS and other studies regarding the potential preventive measures of dietary intake of omega-3 fatty acids for decreasing the risk of advanced AMD,” said Emily Chew, M.D., deputy director, Division of Epidemiology and Clinical Applications and a member of AMDAI's Science Panel. “These results also showed the lack of beneficial effects on preventing progression in persons with early AMD. This may be due to a small number of people who progress from these early stages so the study lacks the power or the ability to answer this question. Nevertheless, these are important results. More studies are definitely needed to clarify what combination of antioxidant supplements and omega 3 fatty acids are recommended for patients. The Age-Related Eye Disease Study 2 (AREDS2) will address this and other questions.”
Test results also conclude that it is very beneficial to have a diet rich in low glycemic index (GI) foods, such as whole grain bread for example. 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 study suggests that substituting five slices of wholegrain bread for white bread every day out of a total intake of 250 g of carbohydrate might cut out almost 8% of advanced AMD over five years.
