The Brain Knows its a Diet Drink

UTRECHT, The NetherlandsFormulators may have made the taste match, but a new study says the brain can tell the difference between caloric and non-caloric versions of a sweet drink (Neuroimage. 2011 Jan 15;54(2):1367-74).

Researchers from the University Medical Center in Utrecht noted sensory-specific satiety, which is defined as a decrease in pleasantness," is increased by greater orosensory stimulation. Both sensory-specific satiety and pleasantness affect taste activation in the orbitofrontal cortex of the brain, which is involved in decision making, reward and emotion.

In contrast, they wrote, metabolic satiety, which results from energy intake, modulates taste activation in reward areas, such as the amygdale and the striatum. The amygdala is located about two inches behind the ears and is involved in emotional memory, but it also plays a role in processing sensory cues (like taste) as they relate to rewards. The striatum is activated by stimuli associated with reward.

In this randomized, crossover study, the brains of 10 men were scanned twice: after fasting for at least 2 hours, and after ingesting 450 mL of orangeade (sweetened with 10-percent sucrose or non-caloric sweeteners) at 150 mL/min, with either small (5 mL) or large (20 mL) sips, on four occasions. During scanning, subjects alternately tasted orangeade, milk and tomato juice and rated its pleasantness. Before and after the scans, subjects rated pleasantness, prospective consumption, desire to eat and sweetness for all drinks.

Before treatment, the amygdala was activated more by non-caloric than by caloric orangeade. Caloric orangeade activated part of the striatum before, but not after treatment. Both the caloric and non-caloric drinks showed activity in the orbitofrontal cortex, but the diet drink activated this area more than the regular drink.

The researchers didnt look into the effects of this brain activity on activity, such as total calorie consumption. But they did show the brain responds differentially to caloric and non-caloric versions of a sweet drink, and consumption of calories can modulate taste activation in the striatum

They also noted they observed no main effects of sip size on taste activation and no interaction between sip size and caloric content.