The findings of a previous study that would have been good news for chocolate lovers have been challenged by the results of newer research.
A 2018 report concluded that consumption of dark chocolate could result in short-term improved vision. However, a new, similarly designed study did not reach this conclusion.
“In contrast to a previous trial reporting beneficial effects of dark chocolate flavanol on visual function, this similarly sized trial did not find any effects on subjective (visual function) or objective (retinal perfusion) end points,” the study authors announced in the newer report. Both reports were published in JAMA Ophthalmology.
The original study was a randomized trial of 30 patients without pathologic eye disease who consumed either a dark or milk chocolate bar. The primary outcomes were visual acuity measured in logMAR units and large- and small-letter contrast sensitivity, which were measured 1.75 hours after chocolate consumption.
The patient population included 21 women and nine men with a mean (SD) age of 26 (5) years. Small-letter contrast sensitivity was much higher among the dark chocolate cohort (mean 1.45 logCS) compared to those who ate milk chocolate (mean 1.30 logCS). Large-letter contrast sensitivity was also higher—but not as significantly higher—in the dark chocolate group (mean 2.05 logCS) than the milk chocolate group (mean 2.00 logCS). There was a slight improvement in visual acuity after dark chocolate consumption (mean, −0.22 logMAR; visual acuity, approximately 20/12) and milk chocolate (mean, −0.18 logMAR; visual acuity, approximately 20/15).
“Contrast sensitivity and visual acuity were significantly higher 2 hours after consumption of a dark chocolate bar compared with a milk chocolate bar, but the duration of these effects and their influence in real-world performance await further testing,” the authors concluded.
Newer Chocolate Research Sees Results Differently
The present study was also a randomized one and included 22 patients who consumed either 20 g of dark chocolate containing 400 mg of flavanols or 7.5 g of milk chocolate. They underwent vision assessments two hours after consumption.
“The primary end point was macular retinal perfusion quantified as vessel density on OCT [optical coherence tomography] angiography. The secondary end point was subjective visual function (Early Treatment Diabetic Retinopathy Study visual acuity, Pelli-Robson chart, and Mars chart contrast sensitivity),” the authors wrote.
In this study, 13 patients were female, and the mean age was 27.3 years. There were no changes in retinal perfusion after consumption of either dark or milk chocolate (superficial plexus, 48.0% vs. 47.5%; deep plexus, 54.1% vs. 54.0%). There were no change in any of the secondary outcomes, either.
“In contrast to a previous similarly sized randomized clinical trial reporting beneficial effects on visual function, no short-term effects of flavanol-rich dark chocolate on automatically assessed retinal blood flow on OCT angiography or subjective visual function were observed in this study. 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 researchers concluded.
The newest findings may be disappointing news not only for chocolate-loving patients, but providers with a sweet tooth, too: Dr. Gareth Lema, a retina surgeon at New York Eye and Ear Infirmary of Mount Sinai in New York City, told Reuters in an interview that the results left him “disappointed.”
“I like chocolate,” he said.