Feast your eyes on this: Dark chocolate sharpens vision, study finds

Is there nothing chocolate cannot do? According to a new study in JAMA Ophthalmology, eating dark chocolate resulted in small improvements in visual acuity and contrast sensitivity for at least 2 hours.

“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,” wrote authors led by Jeff C. Rabin, OD, MS, PhD, professor and chief, Visual Neurophysiology Service, Rosenberg School of Optometry, University of the Incarnate Word, San Antonio, TX.

Other studies have suggested that flavanols in chocolate may enhance blood flow to the central and peripheral nervous systems, and improve cardiovascular function. For this crossover study, 30 participants (9 men, 21 women; mean age 26 years) were “dosed” a 47-g dark chocolate bar with 316.3 mg of flavanols. Later in the study, they ate a 40-g milk chocolate bar with 40 mg of total flavanols—8 times less than the dark chocolate bar.

Within 2 hours of eating each bar, the participants had comprehensive eye examinations. Subjects who had eaten the dark chocolate bar showed significantly higher small-letter contrast sensitivity than those who had the milk chocolate bar.

“This translates to a 1.4 X or 40% improvement in contrast sensitivity after dark chocolate—not huge but comparable to the improvement in contrast sensitivity on gains by using two eyes vs one, which is significant under low-light, impoverished environments,” Dr. Rabin told MDLinx.

Large-letter contrast sensitivity was also higher, and high-contrast visual acuity was slightly improved, in the participants who ate dark chocolate. 

“Our study was much larger in scope than that presented in the JAMA Ophthalmology Brief Report—including color vision, effects of distraction on performance, marksmanship, and various objective visual electrodiagnostic tests—the results of which will be reported subsequently,” Dr. Rabin explained.

If polyphenol flavanols in dark chocolate do enhance blood flow and increase metabolic supply, then the highly vascularized retina may be one of the most susceptible parts of the body to receive these effects, the authors suggested.

“We are considering several follow-on studies, including one which may include optical coherence tomography angiography—a noninvasive technique which provides real-time information about retinal blood flow,” Dr. Rabin said.

Anyone who wants to participate in this study to eat chocolate and undergo noninvasive testing will have to get in line. Probably a long, long line.