Fatty Acids in Fish Oils May Protect Against Diabetic Retinopathy

Dietary consumption of marine polyunsaturated fatty acids (PUFAs) may protect against the development and progression of diabetic microangiopathy, including retinopathy, according to a study published in Acta Ophthalmologica. 

Diabetic retinopathy represents one of the main causes of legal blindness among adults worldwide. In previous controlled animal studies, PUFAs have demonstrated a protective effect against the development of diabetic retinopathy. Moreover, a human prospective study has suggested that taking fish oils decreased the risk of serious sight threatening diabetic retinopathy in middle aged and older individuals with type 2 diabetes mellitus. 

Researchers conducted an observational study on a Norwegian West Coast diabetic population with a high dietary intake of fish oils. This study sought to elucidate the influence of dietary consumption of marine PUFAs on the development of diabetic retinopathy. The investigators recorded the frequency of visual impairment and diabetic retinopathy in a referred diabetic population. From November 2009 to March 2011, 514 diabetic patients were consecutively recruited for the study. But 4 of them refused to be enrolled.

Among the diabetic study population, 50 patients had type I (40% women) and 460 patients had type II (47.4% women). The following parameters were registered: self-reported medication, diet supplements, HbA1c and fish intake. 

Among the type I group, the median age was 44 (age range: 13-87 years) and the median diabetes mellitus diagnosed duration was 11.5 years. Among the type 2 group, the median age was 66 (age range: 27-92 years) and median diabetes mellitus diagnosed duration was 8 years.

In the type I group, 48% had photographic evidence of diabetic retinopathy, 16% had proliferative retinopathy (PDR), and 12% had diabetic macular edema (DME). In the type 2 group, 23.6% had diabetic retinopathy, 3% had PDR, and 5% had DME. 

All patients in the type I group had best-corrected visual acuity (BCVA) of 0.5 (log MAR 0.3) or better in the best eye. A total of 98% of patients in the type 2 group had best eye BCVA at or better than 0.5 (log MAR 0.3) in the best eye.

The average number of fish meals per week in the type 1 group was 3.2 (range: 0-10). The average number of fish meals per week in the type 2 group was 4.4 (range: 0-11). The researchers noted that 44% of patients with type 1 diabetes and 55% of patients with type 2 diabetes consumed omega-3 supplements regularly. When combined, the average consumption of fish meals or omega-3 supplement, or both, per week was 6.2 (range: 0-10) in the patients with type 1 diabetes, and 7.9 (0-12) in the patients with type 2 diabetes. 

The study notes several limitations. The exclusion of 199 patients with known visual data yielded a certain degree of selection bias in the cohort. Additionally, researchers failed to demonstrate statistical significance regarding the relationship between fish oil consumption and visual parameters or retinopathy in the regression models.

This study shows that consumption of PUFA may play a protective role against sight threatening diabetic retinopathy.

“It seems safe to conclude that daily normal intake of fatty fish and/or fish oils may prove to be an important low-cost prophylaxis against diabetic microangiopathy with little risks,” according to the study. “Further carefully designed multicenter studies including monitoring of serum PUFA levels are needed to settle this important issue.”

Reference 

Alsbirk KE, Seland JH, Assmus J. Diabetic Retinopathy and Visual Impairment in a Norwegian Diabetic Coast Population with a High Dietary Intake of Fish Oils. An Observational Study. Acta Ophthalmol. Published online September 2, 2021. doi:10.1111/aos.14977