Sweets on the brain

Sugar-free sweeteners fool the body’s internal computer

Many diet sodas are sweetened without sugar, but those sweeteners may fool your brain as well as your taste buds. ValentynVolkov/iStockphoto

Diet soft drinks usually have no sugar. But that does not mean they’re not sweet. These beverages often contain ingredients that mimic sugar’s sweetness without the big calorie count. In a new study, scientist report that sugar-free sweeteners confuse not only taste buds but also the brain.

Previous studies have found a surprising connection between gaining weight and drinking diet soda. The new study may help explain why. The brains of people who regularly drink diet soda get mixed up keeping track of calories, say the scientists. And that deception may lead people to overeat.

Erin Green and Claire Murphy work at San Diego State University and the University of California, San Diego. They gave taste tests to 12 people who rarely or never drink diet soda and to 12 others who drink the beverages regularly. Each volunteer consumed small amounts of water sweetened with either sugar or saccharin, a popular sugar substitute. The recruits randomly received samples of both types of liquid. While the volunteers drank, the researchers collected images of activity in the tasters’ brains.

Many differences in brain activity emerged that suggested a connection between diet soda consumption and problems with eating appropriately. One of the most important differences was in a region called the caudate (KAW-dayt) head, near the brain’s center. Previous studies have shown that this region is less active in obese people. Similarly, the new study found that people who regularly drink diet sodas had less activity in this region when they were drinking saccharin.

Scientists have been suspecting for years that artificial sweeteners throw off the brain’s calorie counters. In 2010, another team of scientists showed that when rats were sometimes — but not always — fed foods with sugar-free sweeteners, they ate more food. These animals also got fat.

Susan Swithers of Purdue University in West Lafayette, Ind., led that study. “The brain normally uses a learned relationship between sweet taste and the delivery of calories,” she told Science News. That helps the brain regulate food intake.” But when that relationship gets thrown off, she explained, the brain “suddenly has no idea what to expect.”

Power words

obesity Extremely overweight.

psychology The scientific study of the human mind, especially as it affects behavior.

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