September 30, 2019
2 min read

Dark chocolate not shown to benefit retinal blood flow, visual function vs. milk chocolate

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Study participants who consumed flavanol-rich dark chocolate experienced no beneficial effects in retinal perfusion or visual function compared with those who consumed milk chocolate.

The randomized, controlled, masked double-blind crossover study included 22 participants with normal binocular function and no ocular disease. Each participant consumed either 20 g of flavanol-rich dark chocolate, totaling 400 mg flavanol intake, or 7.5 g milk chocolate, with a total flavanol amount of approximate 5 mg.

Before and 2 hours after chocolate consumption, researchers performed a binocular assessment of subjective visual function, including testing with an ETDRS chart at 4 meters with prescribed corrective glasses or contact lenses. Objective measures were assessed with OCT angiography cube scans of 3 mm × 3 mm and 6 mm × 6 mm before and after chocolate consumption on the right eye of each participant.

The primary outcome measure was change in retinal perfusion attributable to dark chocolate consumption, according to the study, while secondary measures included ETDRS visual acuity and contrast sensitivity.

Compared with milk chocolate, dark chocolate consumption had no significant improvements in retinal vessel density at the posterior pole. At OCT angiography of 3 mm, vessel density was 48% after dark chocolate vs. 47.5% after milk chocolate in the superficial plexus and 54.1% for dark chocolate versus 54% for milk chocolate in the deep plexus. Similarly, no significant differences were noted at 6 mm.

Compared with milk chocolate, there were no statistically significant differences in secondary outcomes for dark chocolate.

“As this small trial does not rule out the possibility of benefits, further trials with larger sample sizes would be needed to rule in or out possible long-term benefits confidently,” the study authors wrote.

“The negative conclusions of [this] second study are more convincing because of their addition of optical coherence tomography angiography as an objective corollary method to go with the subjective contrast sensitivity and visual acuity measurements, but critics could argue that there is not yet any proof that improving macular perfusion actually enhances visual performance in healthy human participants,” Paul S. Bernstein, MD, PhD, wrote in an invited commentary to the study. – by Robert Linnehan

Disclosures: Siedlecki reports he received previous speaker fees and travel expenses from Novartis Pharma, Carl Zeiss Meditec, Oculentis OSD Medical and Pharm-Allergan and received personal consultation fees from Bayer. Please see the study for all other authors’ relevant financial disclosures. Bernstein reports no relevant financial disclosures.