Research suggests artificial sweeteners like saccharin and aspartame trick our brains into being unable to control our energy intake.
Critics of New York's proposed soda ban have pointed out that the measure contains some major loopholes. Convenience stores would still be free to sell large, sugary drinks, for example. Sweetened alcoholic beverages are also exempted from the bill. And researchers Mayor Bloomberg cited think the whole thing might backfire. But perhaps the biggest omission in Mayor Bloomberg's plan has to do with an entirely other class of fizzy, sweetened drink: diet sodas.
In fairness to Bloomberg, the science up until now linking diet beverages to poorer health outcomes has been inconclusive, at best. We think there might be a connection to heart attack and stroke, but many researchers challenge those findings. Another study has associated diet soda with bigger waistlines, but there again, the scientists couldn't confirm whether the relationship was causal.
The murky waters of diet soda science may have just gotten a little clearer, though. New research shows that the sugar substitutes used in diet beverages actually change how our brains' reward areas work.
Researchers took 24 young adults, half of whom were habitual diet soda drinkers who consumed a sugar-free beverage once a day or more. The other half avoided diet soda. Hooking them up to brain scanning equipment, the scientists fed each group of study participants a stream of water sweetened alternately by natural and artificial sweeteners.
Because the brain's reward center is also responsible for controlling energy intake and the motivation to eat, the scientists believe that their results help explain why diet sodas appear to drive people to consume more food than they should:
One of the strongest links seen was diminishing activation of an area known as the caudate head as a recruit's diet soda consumption climbed. This area is associated with the food motivation and reward system. Green and Murphy also point out that decreased activation of this brain region has been linked with elevated risk of obesity.
"The brain normally uses a learned relationship between sweet taste and the delivery of calories to help it regulate food intake," Swithers explains. But when a sweet food unreliably delivers bonus calories, the brain "suddenly has no idea what to expect." Confused, she says, this regulator of food intake learns to ignore sweet tastes in its predictions of a food's energy content.
It's worth remembering that this is a small-scale study, performed in a way that leaves room for error. Still, it's the latest report suggesting that a scientific connection may exist between diet sodas and poor health -- a finding that could expand the scope of anti-obesity efforts.
Via Paul Kedrosky