Previous findings suggest that chocolate rich in flavonols — a group of related compounds — could improve blood flow in the heart and brain, but an optometrist and his colleagues from the University of the Incarnate Word in Texas wanted to find out if it could benefit eyesight, too. RELATED: 7 Heart-Healthy Perks of Dark Chocolate Although the research doesn’t suggest replacing a balanced diet with sweets, it’s still a bit of encouraging news for those who enjoy dark chocolate. In the study, published April 26, 2018, in the journal JAMA Ophthalmology, a trio of researchers examined the effects of eating milk chocolate versus dark chocolate on various aspects of vision, including visual acuity (how sharp your vision is) and contrast sensitivity (ability to distinguish objects from their background). To test out the two types of chocolate, 30 healthy adults, a majority whom were female and in their mid-twenties, were given a Trader Joe’s Crispy Rice Milk Chocolate bar, and, a few days later, a Trader Joe’s Dark Chocolate bar. The study was single-blind, meaning the participants themselves were not told which type of chocolate they were given. If you’ve had dark chocolate, though — particularly one that’s 72 percent cacao, what the participants had, or higher — you’d know it’s very easy to tell apart its bitter taste from more sugary milk chocolate. But the authors don’t feel this influenced the study, considering the participants weren’t informed of the intent of the research. After eating each type of chocolate, the participants completed a number of vision exams. Two hours after eating the dark chocolate, they had an improvement in small-letter contrast sensitivity. “Normally there are black letters on a white background and the letters get smaller,” lead study author Jeff Rabin, PhD, a professor at the University of the Incarnate Word Rosenberg School of Optometry in San Antonio, Texas, says, explaining the typical eye chart at doctor’s offices. “With contrast sensitivity, the brightness of the letter increases until it’s eventually very difficult to see, so that’s what we were measuring using small letters.” RELATED: 10 Tips to Protect Your Vision and Prevent Blindness Results of the small-letter test revealed that participants had improved eyesight that translated to about 40 percent, Dr. Rabin says, which he explains is comparable to using two eyes versus one. The improvement is notable, but it’s also important to point out the small sample size of participants. Additionally, the authors failed to address sugar intake, says Andrew Morgenstern, doctor of optometry, fellow of the American Academy of Optometry and diplomate in the American Board of Optometry, based in Chevy Chase, Maryland, who was not involved in the study. A review published in September 2015 in the journal Critical Reviews in Clinical Laboratory Sciences suggested eating too much sugar is linked to obesity, heart disease, and type 2 diabetes. RELATED: The Best Ways to Enjoy Dark Chocolate When You Have Diabetes “Diabetes is rampant in today’s population, and obviously the short-term effect of eating chocolate is one thing,” Dr. Morgenstern says. “While it might give them a short-term boost in visual acuity, what happens in the long term? That would be the caveat. Dietary intake has to be addressed.” Rabin and his coauthors urge that they don’t mean we should all pick up a bar of chocolate if we’re hoping to have sharp eyesight. “This is not anywhere near prescription. This is very early, and it’s a very small effect,” says Rabin. “I don’t know the duration of the effect or long-term effects on vision — that awaits further study.” And that’s not the only good news for dark chocolate. It may also help reduce stress and inflammation, suggests findings from two studies presented at the Experimental Biology 2018 annual meeting in San Diego, which has yet to be published in a peer-reviewed journal. Lee Berk, doctor of public health and professor at Loma Linda University in California, found that human subjects who consumed chocolate with high cacao content had a short-term improvement in brain function and cellular response. But just like the previous study, Dr. Berk’s experiments also had an extremely small sample size — 10 participants total. “Research such as this [on chocolate], while it is sometimes entertaining, is just as valuable as research that we consider more important, such as cancer research, because we never know where answers to everyday health problems are going to come from,” Morgenstern says.
