People who ate a dark chocolate bar (72 percent cacao) had better vision within two hours, compared to those who consumed a milk chocolate bar in a small study conducted at the University of the Incarnate Word Rosenberg School of Optometry in San Antonio, Texas.
The study, which was published in JAMA Ophthalmology, involved 30 participants, average age 26, who did not have eye disease. Participants ate a dark chocolate bar and underwent eye testing a couple of hours later. An average of eight days later, they completed the same process again, after eating a milk chocolate bar.
Researchers found that eating dark chocolate produced small improvements in visual acuity and contrast sensitivity that lasted a short time. The researchers speculate that improved vision after eating dark chocolate could be related to increases in the retinal visual pathway and/or to improved cerebral blood flow.
Dark chocolate contains polyphenolic flavonoids, which have been shown to have a number of health benefits.