Bad news for chocolate lovers: it may not help your vision

In disappointing news for chocolate lovers, researchers have found that contrary to an earlier report, eating dark chocolate will not improve your vision.

The earlier report suggested that certain aspects of vision improved within a couple of hours of chocolate consumption. The new study showed no changes in vision or blood flow to the eyes after consuming about three quarters of an ounce of dark chocolate. Both studies, however, involved only a small number of volunteers.

With two similar-sized trials yielding opposite results, “more research is needed,” said the authors, led by Dr. Jacob Siedlecki of Ludwig-Maximilians-University in Munich. “As this small study 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,” Siedlecki and his colleagues write in JAMA Ophthalmology.

The authors did not respond to a request for comment.

The reason for suspecting dark chocolate might help with vision is that the sweet treat is bursting with flavonoids, which are antioxidants. Studies have shown that supplements with high levels of antioxidants can reduce the risk of an age-related vision problem called macular degeneration. The specific flavanol in dark chocolate has also been shown to dilate blood vessels, the researchers note.

To see if the earlier study on chocolate and vision could be duplicated, Siedlecki and colleagues rounded up 22 healthy volunteers, ages 20 to 62, who had no vision issues. The volunteers were randomly assigned to consume either a 20-gram (0.71 oz) piece of dark chocolate - equivalent to about a quarter of a dark chocolate candy bar and containing 400 milligrams of flavanols - or 7.5-gram piece of milk chocolate containing roughly 5 mg of flavanols.

Volunteers’ eyes were checked with a relatively new, high-tech scanner that shows blood vessels in detail, before they consumed their chocolates and two hours after. Siedlecki’s team was looking for signs that the chocolate had dilated the blood vessels in the retina, which would mean volunteers were getting better blood flow to the eye.

Volunteers were also given low-tech vision tests similar to the ones used in the earlier chocolate study.

One week after the initial run, the volunteers who got dark chocolate the first time were given milk chocolate and those who got milk chocolate the first time were given dark chocolate.

When the researchers analyzed their data, they found no significant differences in the retina scans or the vision tests when volunteers consumed dark chocolate or milk chocolate.

Dr. Gareth Lema was “disappointed” to read about the new results. “I like chocolate,” he explained.

While the new study didn’t show any benefit to consuming a single piece of chocolate, “that doesn’t mean eating it over the long term isn’t beneficial,” said Lema, a retina surgeon at New York Eye and Ear Infirmary of Mount Sinai in New York City.

Even in the first study, the positive results were quite small, Lema said. “Neither study really showed that if you eat a piece of chocolate, you’ll have eagle eye vision,” he added.

As for the impact of a daily “dose” of dark chocolate, the jury’s still out on that, Lema said.

Dr. Jay Chhablani agreed. “This is one of the limitations of both studies,” said Chhablani, an associate professor of ophthalmology at the University of Pittsburgh School of Medicine in Pennsylvania. “Someone has to do a long-term study comparing dark chocolate to milk chocolate.”