Findings from Spanish researchers suggest that, along with lowering the risk of cardiovascular disease and possibly age-related macular degeneration, the Mediterranean diet may also protect against diabetic retinopathy, a sight-threatening complication of diabetes. Many researchers suspect the reason is that the Mediterranean diet is rich in fish oil, also called omega-3 fatty acids.
In the study, called PREDIMED, researchers randomly divided volunteers into groups that followed a Mediterranean diet, supplemented with olive oil or mixed nuts, or a low-fat diet. Those on the Mediterranean diet had 30 percent fewer strokes, heart attacks, or deaths from cardiovascular disease.
After the study was completed, researchers conducted an analysis, published in JAMA Ophthalmology, that involved 3,482 adults, with an average age of 67, who had type 2 diabetes. During the six-year follow-up, the group had 69 new sight-threatening diabetic retinopathy complications requiring treatment. Among those consuming less than 500 mg a day of omega-3 fatty acids from seafood, there were 52 cases. Among those consuming 500 mg or more, there were only 17 cases, suggesting that omega-3 fatty acids-the equivalent of about two servings of fatty fish a week-are strongly associated with a decreased risk of diabetic retinopathy.
The retina is rich in omega-3s, and lab research has found that higher levels of these fats have a protective effect against diabetic retinopathy, according to the researchers. Nevertheless, an observational study like this cant say conclusively that omega-3 fatty acids are responsible for the difference between the two groups. Other lifestyle factors may play a role. But the authors noted that the evidence overall suggests that diets containing fatty fish (the study did not look at omega-3 supplements) may be beneficial for several diseases with little downside.