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 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.
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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."
SOURCE: https://bit.ly/2n45gHZ and https://bit.ly/2nBJonR JAMA
Ophthalmology, online September 26, 2019.
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