Omega-3s for Protection Against Diabetic Retinopathy? Best Look Elsewhere, Study Concludes

There are lots of clues that the omega-3 fatty acids found in cold-water fish such as salmon and some nuts such as walnuts might be good for the eyes and, more particularly, for retinas because of their anti-inflammatory and vasodilating effects. Research findings have also hinted that omega-3 fatty acids might be particularly beneficial for people with type 2 diabetes, affording them some protection against the development of diabetic retinopathy.

Results reported in the May 2024 issue of Ophthalmology may not completely vanquish the hope fed by those clues and hints, but they do cast some serious doubt on taking omega-3 fatty acid supplements as a relatively easy and inexpensive way to lower the risk of diabetic retinopathy.

Emily Sammons, MBChB, D.Phil., of the Clinical Trial Service Unit and the Epidemiologic Studies Unit of the University of Oxford in the United Kingdom, and her colleagues found no difference in the incidence of retinopathy among those who were randomly assigned to take 1-gram capsules of omega-3 fatty acids (460 milligrams [mg] of eicosapentaenoic acid and 380 mg of docosahexaenoic acid) for six and a half years and those randomly assigned to a placebo. They also didn’t find any differences between the treatment and placebo groups on a variety of secondary and tertiary end points related to the severity of the retinopathy or loss of visual acuity.

Sammons and her co-authors said the observational studies that have shown benefits from omega-3 fatty acids may have been confounded by unknown or unmeasured variables. Their results, in contrast, came from a large, randomized prospective study. “As such, no studies of equivalent quality exist with which it is comparable,” Sammons and her colleagues wrote in the discussion section of the study.

The data for the analysis they conducted didn’t come from a study that was designed to investigate whether omega-3 fatty acids were protective against retinopathy. The ASCEND trial was a randomized, prospective study designed to whether taking omega-3 fatty acids capsules daily would influence the risk of serious cardiovascular events. Sammons and her colleagues linked up data from the ASCEND trial to data from a National Health Service program in England and Wales to screen people with diabetes for retinopathy. Of the 15,480 people in the ASCEND, Sammons and her colleagues identified 7,360 who had screened for retinopathy. In that group, 548 of the 3,692 (14.8%) who taken the omega-3 fatty acid capsules developed “referable disease,” a composite of retinopathy and maculopathy scoring based on grading system used by the United Kingdom screening committee. Among the 3,668 who were randomly assigned to placebo, 513 (13.9%) developed referable disease.

“Representing the largest prospective test of its kind to date, these data exclude any clinically meaningful benefits” of 1 gram of omega-3 fatty acids on diabetic retinopathy,” Sammons and her colleagues wrote in the abstract of the study.