Nutritional supplements may fight diabetic retinopathy

Nutritional supplements can improve colour vision, contrast sensitivity and other measures of visual functioning in people with diabetes -- with or without retinopathy, researchers say.

The nutrients could offer a new line of defense against diabetic retinopathy, said the researchers from four US states. They published the findings from the Diabetes Visual Function Supplement Study (DiVFuSS) June 2015, in the ­­­­­­­British Journal of Ophthalmology.

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While pharmaceuticals and photocoagulation can often successfully treat diabetic retinopathy, they don’t work adequately in many patients. At the same time, the Age-Related Eye Disease Study (AREDS) demonstrated that a nutritional supplement could slow the progress of age-related macular degeneration. This led the researchers to wonder whether supplements might prevent or treat diabetic retinopathy. So investigators gave 39 patients a formulation of micronutrients that had previously shown effects related to vision or the etiology of diabetes (EyePromiseDVS, Zea Vison, St. Louis, Missouri.)

The formula consisted of vitamins C, D3 and E (d-a tocopherol), zinc oxide, eicosapentaenoic acid, docosahexaenoic acid, a-lipoic acid (racemic mixture), coenzyme Q10, mixed tocotrienols/tocopherols, zeaxanthin, lutein, benfotiamine, N-acetyl cysteine, grape seed extract, resveratrol, turmeric root extract, green tea leaf, and Pycnogenol (patented French Maritime Pine Bark extract, sp Pinus pinaster, Horphag Research, Geneva, Switzerland).

In animal trials, the formula had attenuated diabetes-induced metabolic abnormalities in the retina, including oxidative stress, mitochondrial damage and upgregulation of inflammatory mediators, the researchers said.  And it prevented the formation of degenerative capillaries in the retinal microvasculature.

Twenty-seven of the patients in DiVFuSS had type 1 diabetes, and 40 had type 2 diabetes.

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Fifteen had mild to moderate diabetic retinopathy, and 24 had no diabetic retinopathy. All patients took two gel capsules per day. The 15 with mild to moderate retinopathy took two capsules of the supplements. The 24 without diabetic retinopathy took one capsule of the supplement and one capsule of an identical-looking placebo. Another 28 patients took the placebo alone.  In this group, 11 had type 1 diabetes and 17 had type 2 diabetes. Fifteen had retinopathy and 13 did not.

Next: Study results

The researchers asked the patients to refrain from taking additional supplements that included the ingredients of the formula being studied, with the exception of one multi-vitamin per day. They also asked the patients not to eat food high in xanthophylls or omega-3 fatty acids more than twice per week.

Study results

·      After 6 months, macular pigment optical density (MPOD) had increased by a mean of 27% in the supplemented group but decreased by a mean of 2% in the placebo group. The difference was statistically significant (P < 0.0001).

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·      Contrast sensitivity, colour error score and visual field mean sensitivity also significantly improved in the supplement group when compared to the placebo group. (P ≤ 0.008).

·      Mean changes in high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and trigylcerides also favored the supplement group (P ≤ 0.01)

·      High-sensitivity C-reactive protein (hsCRP) levels decreased by a mean of 60% in the supplemented group, versus a decrease of 11% in the placebo group (P = 0.01).

·      Mean 25-OH-vitamin D3 levels were significantly higher (P = 0.02) in the supplement group.

·      A third of the supplemented subjects reported a one unit decrease in symptoms compared with 3.6% of the subjects on placebo (P = 0.0024).

There were no statistically significant differences between the groups in mean foveal or mean retinal nerve fibre layer (RNFL) thickness, glyocohaemoglobin (HBA1c), total cholesterol or tumour necrosis factor α (TNF-α).

Next: Important evidence with clinical implications

Important evidence with clinical implications

The lack of a difference in foveal or RNFL thickness was not surprising because the subjects had little macular pathology at baseline and the trial was short, the researchers wrote.

The authors also noted some limitations. Serum levels of the formula’s various constituents were not measured. And the inclusion of multiple components in the test formula precludes strict analysis of synergistic or inhibitory effects of its constituents.The trial took place at only 1 centre. It was funded by ZeaVision, and one of the authors was an employee of the company.

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Nevertheless, the study provides important evidence for a nutritional approach to diabetic retinopathy.

"DiVFuSS demonstrates that clinically meaningful improvements in visual function can be realised with a novel, multicomponent nutritional formula in patients with long or short term diabetes duration, whether Type 1 or 2," said Dr. A. Paul Chous, lead investigator of the study, in a press release.