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Omega-3 Intake Associated with a Lower Risk of Incident Diabetic Retinopathy

Omega-3s & the Risk of Diabetic Retinopathy

Although treatment of diabetic retinopathy may slow the progression of vision loss, it usually won’t cure the condition or restore normal vision. Thus, the best treatment for diabetic retinopathy is prevention. Strict control of blood glucose is one means of significantly reducing the long-term risk of vision loss. Also of interest is the relationship between intake of long-chain omega-3 polyunsaturated fatty acid (LCω3PUFAs) and risk of diabetic retinopathy.

The retina is rich in LCω3PUFAs, which are substrates for the formation of oxylipins – compounds with anti-inflammatory and anti-angiogenic activity. Inflammation and angiogenesis are important molecular factors in the development and progression of this ocular complication of diabetes.

Although experimental models support a protective role for dietary LCω3PUFAs, clinical data are lacking. This led Spanish investigators of the largescale PREDIMED trial to examine whether LCω3 PUFA intake is associated with a decreased incidence of sight-threatening diabetic retinopathy (1).

Design & Methods

The PREDIMED trial tested Mediterranean diets supplemented with olive oil or nuts vs. a control diet for primary cardiovascular prevention. For this prospective trial, researchers recruited 3,614 participants (aged 55-80) in the PREDIMED trial with a previous diagnosis of type 2 diabetes. Full data was available for 3,482 participants.

The frequency of consuming eight types of seafood was determined using a validated questionnaire at baseline, and habitual seafood consumption was tracked over time. Participants were assessed as meeting or not meeting the dietary LCω3PUFA recommendation of at least 500 mg daily for primary cardiovascular prevention. The main outcome measure was incident sight-threatening diabetic retinopathy – i.e. requiring laser photocoagulation, vitrectomy, and/or anti-angiogenic therapy.

Results

A total of 2,611 participants (75%) met the target LCω3PUFA recommendation. During a median follow-up of 6 years, 69 new events were documented. After adjusting for age, gender, intervention group, as well as lifestyle and clinical variables, those who consumed at least 500 mg LCω3PUFAs at baseline were 48% less likely to develop incident sight-threatening diabetic retinopathy compared to those consuming less (HR 0.52, p = 0.001). The association was slightly stronger for yearly updated LCω3PUFA intake.

Conclusion

In middle-aged and older type 2 diabetics, intake of 500 mg or more of LCω3PUFAs daily is associated with a decreased risk of vision-threatening diabetic retinopathy. The results are consistent with findings from experimental models and the current model of diabetic retinopathy pathogenesis. The target intake is achievable by eating at least 2 servings of oily fish weekly.

Comments

Since the Mediterranean diet incorporates fish and chicken at the expense of red meat, it is not surprising that 75% of participants met the marine omega-3 goal. In the U.S., however, a recent analysis (2) of the National Health and Nutrition Examination Survey shows that a large percentage of our population is not meeting recommendations for omega-3 fatty acid consumption. Median intakes of EPA and DHA were found to be 18 mg/day and 50 mg/day, respectively.

References

1. Sala-Vila A, et al. Dietary marine omega-3 fatty acids and incident sight-threatening retinopathy in middle-aged and older individuals with type 2 diabetes. JAMA Ophthalmol Epub ahead of print Aug. 18, 2016.
2. Papanikolaou Y, et al. U.S. adults are not meeting recommended levels for fish and omega-3 fatty acid intake: results of an analysis using observational data from NHANES 2003–2008. Nutr J 13:31, 2014.