Anyone who has ever smoked marijuana is well aware that this drug induces the consumption of food, particularly sweet tasty foods. Neuroscientists have used this action of the drug to explore the mechanisms within our brain that make us crave sweets and how we control our appetite. We have discovered that our brain’s endogenous cannabinoid system does far more than just induce us to eat; it also rewards us with a feeling of euphoria for doing so.
I was recently honored by an invitation to give a TED talk on this idea. The video is available here. http://www.youtube.com/watch?v=4SvkaK2Al0o&feature=plcp
A group of scientists, led by Maria Antonietta De Luca from the University of Cagliari in Italy, recently published a study in the journal Neuropharmacology that investigated specific brains regions that allow the active ingredient in marijuana, delta-9-tetrahydrocannabinol (THC), to induce pleasure when eating tasty foods and how THC is able to induce people to choose sugary foods over all others. They wanted to know whether, and how, THC made all foods more enjoyable—even those that are usually quite unpleasant, such as quinine or highly concentrated salt solutions (think of the solution you drank to prep for a colonoscopy!).
The scientists discovered that THC increased the pleasurable response to eating sugar but had no effect upon how much we dislike the taste of other types of foods. For example, if you hate eating peas or broccoli or whatever, smoking marijuana will not induce you to like eating them. If marijuana could induce young people to eat their vegetables then possibly its legal status might be changed—but I doubt it.
The ability of sugar to induce a rewarding feeling requires that THC act within a specific brain region called the “shell of the nucleus accumbens.” Ordinarily when we consume tasty foods, dopamine is released within this brain region to inform us that our brain likes this food and wants us to consume it more often. In the presence of THC significantly more dopamine is released in response to the same amount of sugar-enriched food. So what does all of this mean? Our brain’s endogenous marijuana system ordinarily modulates how good a particular food tastes to us; smoking marijuana simply enhances this natural mechanism in the brain.
© Gary L. Wenk, Ph.D. Author of Your Brain on Food (Oxford University Press)