巧克力爱好者的坏消息：它可能对你的视力没有帮助

Researchers have sad news for chocolate lovers. They found that eating dark chocolate does not improve people's eyesight as had been thought.

An earlier report suggested that some aspects of eyesight improved within one or two hours of eating chocolate. The new study found no changes in vision or blood flow after volunteers ate about 20 grams of dark chocolate. Both studies, however, involved only a small number of test subjects.

With two similar-sized tests producing opposite results, "more research is needed," said the organizers of the latest study. The lead researcher was Jacob Siedlecki of Ludwig-Maximilians-University in Munich, Germany.

Additional testing with larger sample sizes would be needed to rule in or out possible long-term benefits," the researchers wrote. Their report appears in the medical publication JAMA Ophthalmology.

The reason for suspecting dark chocolate might help with vision is that the sweet treat has plenty of flavonoids, which are antioxidants.

Antioxidants are man-made or natural substances that may prevent or delay some forms of cell damage. Studies have shown that foods with high levels of antioxidants can reduce the risk of an age-related vision problem called macular degeneration.

To see if the earlier study on chocolate could be repeated, Siedlecki and his team found 22 healthy volunteers, ages 20 to 62, who had good eyesight.

The volunteers were asked to eat either a 20-gram piece of dark chocolate or a 7.5-gram piece of milk chocolate. The piece of dark chocolate contained 400 milligrams of flavanoids, while the milk chocolate had about 5 milligrams of flavanoids.

Volunteers' eyes were examined with a relatively new, high-tech scanner that shows blood vessels in detail. The volunteers were tested before they ate the chocolate and again two hours later.

Siedlecki's team was looking for signs that the chocolate had enlarged blood vessels in the eye. This means volunteers were getting better blood flow.

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

A week after the test, the people who got dark chocolate the first time were given milk chocolate, and those who had milk chocolate the first time were given dark chocolate.

The researchers said they found no difference in either test when volunteers ate dark chocolate or milk chocolate.

Doctor Gareth Lema was a little sad to read the latest findings. "I like chocolate," he explained.

While the new study failed to show any health benefit to eating a single piece of chocolate, "that doesn't mean eating it over the long term isn't beneficial," said Lema. He works at the New York Eye and Ear Infirmary of Mount Sinai in New York City.

"Neither study really showed that if you eat a piece of chocolate, you'll have (great) vision," Lema added.

Doctor Jay Chhablani agreed.

"Someone has to do a long-term study comparing dark chocolate to milk chocolate," he said. Chhablani is an associate professor of ophthalmology at the University of Pittsburgh School of Medicine.

Both men know it will be easy to find volunteers.

I'm Susan Shand.

The Reuters News Agency reported this story. Susan Shand adapted it for VOA Learning English. George Grow was the editor.

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