In the news: Omega-3 Levels in Blood & Risk for Diabetic Retinopathy

Diabetic Retinopathy (DR) and Omega-3 Fatty Acids

The longer a person has diabetes, the higher the chances of developing diabetic retinopathy (DR). This complication of diabetes is estimated to affect 80% of those who have had both type 1 and type 2 diabetes for 20 years or more.

The American Academy of Ophthalmology explains that high blood sugar levels cause damage to blood vessels in the retina. These vessels can swell and leak, or close and stop blood from passing through. As DR progresses, abnormal new blood vessels can grow on the retina that are fragile and prone to bleed, impacting vision.

When it comes to lowering the risk of DR, it’s essential to control blood sugar, lipids, and blood pressure. But in addition to medications, increasing physical activity and adopting a healthy diet can make a significant difference as well.

Eating more fruits and vegetables rich in flavonoids is tied to a lower risk of DR for example, and there is interest in consuming enough fish as a possible risk-lowering strategy as well.

The eye’s retina is rich in omega-3 fatty acids which have anti-inflammatory activity and may influence new vessel formation. Since inflammation is associated with the development and progression of DR, researchers have long examined whether eating omega-3 fatty acids could be related to DR risk.

One study published in 2017 for example, showed that intake of at least 500 milligrams per day of omega-3 is associated with a decreased risk of sight-threatening DR in middle-aged and older people(1). Eating 500 milligrams of omega-3 daily is achievable with two servings per week of oily fish.

Few studies, however, have looked at actual blood levels of omega-3 in the circulation and whether there’s a relationship between them and DR.

A newly published study(2) has found an association between omega-3 blood levels and a lower risk of DR and having severe DR.

Researchers from several universities and the National Eye Institute analyzed information from diabetic participants in two previous studies (the Multi-Ethnic Study of Atherosclerosis and the Genetics of Latino Diabetic Retinopathy study). The combined studies included 1,356 participants with type 2 diabetes.

The investigators found that individuals with blood levels of the omega-3 fatty acid DHA in the top 25% were 17% less likely to have retinopathy compared to the lowest 25% of DHA blood levels.

Digging deeper into the analysis revealed that people with the highest blood levels of EPA + DHA combined – or DHA alone – had 38% less severe DR compared to those with lowest blood concentrations.

According to the authors, the results of the present study suggest that maintaining ample blood levels of omega-3, particularly DHA, may be helpful in lowering the risk of developing or worsening DR.

Further studies are needed – and warranted – to see whether consuming more omega-3 is a viable approach for those with type 2 diabetes.

Both EPA and DHA fatty acids are abundant in cold water fatty fish such as salmon, anchovies, sardines, and tuna. Bluefin tuna have up to 5 times more DHA than other types of tuna, but keep in mind too, that smaller fish generally contain lower levels of mercury.

Algae and seaweed are also sources of DHA and EPA and may be an important source for those avoiding fish or eating a vegetarian or vegan diet.

References

1. Chew E. Dietary intake of Omega-3 fatty acids from fish and risk of diabetic retinopathy. JAMA. 317: 2226–2, 2017.
2. Weir NL, et al. Omega-3 fatty acids are associated with decreased presence and severity of diabetic retinopathy: A combined analysis of MESA and GOLDR cohorts. Retina. Epub ahead of print Jan, 2023.