Flavanols in dark chocolate are known for having positive effects on heart functions and decreasing the risk of strokes. However, Dr. Jeff Rabin at the University of Incarnate Word's Rosenberg School of Optometry decided to find out if these antioxidants could benefit visions as well.
Study methods and results
Rabin explained the research team recruited 30 young adults in a blinded exam, in which they were tested for their high-contrast visual acuity and small-letter contrast sensitivity around two hours after ingestion of a Trader Joe's 72% cacao dark chocolate bar or a crispy rice milk chocolate bar.
Then they did a cross-over test in which participants originally consuming dark chocolate ate milk chocolate and vice versa.
“Our initial findings showed participants eating dark chocolate had a small improvement [in visual acuity compared to milk chocolate eaters], and we reasoned that this is due to an increase of blood flow either to the retina or andor – the visual part of the brain,” said Rabin.
However, there was a significant improvement in contrast sensitivity test during which they were asked to recognize letters of the same size, but blended into a low-contrast background, he noted.
“We also computed a single composite score, and that shows an approximately 60% improvement in one’s ability in seeing low-contrast targets,” added Rabin.
‘We didn’t measure the duration of the effect…’
Rabin said there are some limitations of the study including that participants may have been aware of the type of chocolate consumed based on taste.
“We didn’t measure the duration of the effect of dark chocolate,” he added. “The effect usually disappears in the body within six hours… so it needs further evaluation.”
Source: JAMA Ophthalmology
Published online ahead of print, doi: 10.1001/jamaophthalmol.2018.0978
“Effects of Milk vs Dark Chocolate Consumption on Visual Acuity and Contrast Sensitivity Within 2 Hours”
Authors: Jeff C. Rabin, OD, MS, PhD; Nirmani Karunathilake, BS, MS; Korey Patrizi, BS