Study: Chocolate cravers love even looking at it

Posted on Sun, Oct. 15, 2006
Study: Chocolate cravers love even looking at it
By Tina Hesman Saey
St. Louis Post-Dispatch
(MCT) ATLANTA

Some people have chocolate on the brain.

A new study of people who crave chocolate shows that eating chocolate, or even just looking at a picture of it, turns on pleasure centers in the brains of cravers far more than in people who don't crave the confection. Viewing pictures of chocolate also activates an area of the brain known to be involved in drug addiction.

The study, by Ciara McCabe and Edmund T. Rolls of Oxford University in England, was one of more than 14,000 presentations slated for the annual meeting of the Society for Neuroscience this week. The meeting draws more than 35,000 brain scientists and doctors each year, making it one of the world's largest scientific gatherings.

McCabe gathered seven chocolate cravers and eight non-cravers for her experiment. All of the subjects completed a survey to confirm their chocolate craving status. The differences were clear. Some people really don't crave chocolate, a fact McCabe - an admitted chocolate craver - finds incredible.

She placed the volunteers in a functional magnetic-resonance imaging (fMRI) machine - a scanner that measures activity in the brain. Once the people were in the scanner McCabe gave them a taste of liquid chocolate. The cravers and non-cravers registered the taste to the same degree in parts of the brain involved in detecting taste. But people who crave chocolate perceived the taste as more pleasant than did the non-cravers. The difference showed up in the brain scan and in the volunteers' ratings of the experience.

McCabe showed her friends pictures of chocolate to find the yummiest-looking examples to use in the experiment, she said. When she showed the mouth-watering pictures of chocolate to cravers, the ventral striatum, a part of the brain involved in drug addiction, turned on. Non-cravers showed no activity in that part of the brain.

Viewing a picture of chocolate while tasting it increased the pleasure of the experience for cravers and non-cravers alike, but the cravers responded far more to the chocolate combination than the non-cravers did. The reaction was particularly strong in a part of the brain called the pregenual cingulate cortex, a reward and pleasure center.

The researchers don't yet know why some people crave chocolate while others don't. The answer could help scientists understand people's food preferences and eating patterns. Such knowledge could be important for helping people change their diets or control cravings.

In a separate presentation, McCabe and Rolls may have settled a debate about whether umami is a fifth human taste, along with bitter, salty, sweet and sour. Umami is a Japanese word that describes meaty flavor associated with the amino acid glutamate. MSG, parmesan cheese and meats are all said to be umami flavors.

The very first taste receptors found on the tongue were for umami - seemingly good evidence that it is a taste. McCabe found that when she gave volunteers some MSG, parts of the brain that register taste became active. That result seems in keeping with umami being a taste too.

But when McCabe combined the odor of vegetables with the taste of MSG, suddenly the brain registered the experience in the pleasure centers, not in the taste centers. And it's not just that people liked the smell of vegetables so much. Salt combined with the vegetable odor didn't light up the pleasure center the way the umami combo did. And giving people a whiff of rum with their dose of MSG produced a rather unfavorable rating from the tasters.

These results might indicate that, as far as the brain is concerned, umami doesn't qualify for taste status.

"I wouldn't stick my neck out and say it's not taste, but we believe it's more of a flavor enhancer," McCabe said.