Investigating the NeuroPRotective Effect of Oral Omega-3 Fatty Acid Supplementation in Type 1 Diabetes (nPROOFS1): a Randomised, Placebo-Controlled Trial

This randomised, double-masked, placebo-controlled trial (ACTRN12618000705280) evaluated the effects of oral omega-3 fatty acid supplementation on peripheral nerves in type 1 diabetes. Participants with type 1 diabetes were assigned (1:1) to omega-3 (fish oil; 1800 mg/day) or placebo (olive oil; 600 mg/day) supplements for 180 days. Primary outcome was change from baseline in central corneal nerve fibre length (CNFL) at day 180. Secondary outcomes included change in other corneal nerve parameters, corneal sensitivity, peripheral small and large nerve fibre function, and ocular surface measures. Efficacy was analysed following intention-to-treat. Safety assessments included diabetic retinopathy grade and adverse events.

Between July 2017 and September 2019, 43 participants received omega-3 (n=21) or placebo (n=22) supplements. All participants, except for two assigned to placebo, completed the trial. At day 180, the estimated increase in CNFL in the omega-3 group, compared to placebo, was 2.70 mm/mm² (95%CI: 1.64-3.75). The Omega-3 Index increased relative to placebo (3.3%; 95%CI: 2.4-4.2). There were no differences in most small or large nerve fibre functional parameters. Adverse events were similar between groups.

In conclusion, this randomised controlled trial found that long-chain omega-3 supplements impart corneal neuroregenerative effects in type 1 diabetes, indicating a role in modulating peripheral nerve health.