The Science Behind the Marijuana Munchies

The link between marijuana and an increased appetite has been well documented by both scientific and casual researchers. Even before states began passing medical marijuana laws, some doctors were quietly recommending the drug to cancer, AIDS and other patients with nausea and poor appetite.

New findings from the Monell Chemical Senses Center and Kyushu University in Japan suggest that marijuana may enhance the sweet taste of foods by acting directly on taste receptors, rather than just in the brain, as had previously been shown. The work enhances scientists' understanding of how THC, the active ingredient in marijuana, acts on the appetite, and could eventually lead to treatments for obesity or lack of appetite.

Fourteen states currently have medical marijuana laws, even though the drug is still illegal under federal law, and some legislators are pushing to legalize it outright. In parts of California, the first state to pass a medical marijuana law, in 1996, marijuana dispensaries have become nearly as common as liquor stores.

But what is it about marijuana that causes "the munchies"—not so much actual hunger as an intense craving for food, especially of the sweet, salty or fatty variety? The new findings from Monell report that endocannabanoids, compounds that are structurally similar to the cannabinoids found in cannabis sativa (marijuana) but occur naturally in the body, act directly on the tongue's taste receptors to enhance the perception of sweetness.

Previously, scientists had believed that cannabinoids regulated appetite mainly by bonding to specific receptors in the brain. As explained in a 2001 article in Nature, researchers found that they could depress appetite in mice by genetically modifying them to be deficient in cannabinoid receptors. Later studies have led to greater understanding of the relationship between the brain's cannabinoid receptors and the hormone leptin, which was found to inhibit hunger.

The Monell study involved a series of experiments on mice to determine their behavioral, cellular and neural responses to sweet taste stimuli before and after the administration of endocannabinoids. In every case, the mice went coo-coo for Cocoa Puffs (well, technically, their "sweet taste responses were enhanced by endocannabinoids"). Interestingly, the effect was not observed with sour, salty, bitter or umami taste stimuli.

The press release from Monell notes that, "sweet taste receptors are also found in the intestine and the pancreas, where they help regulate nutrient absorption, insulin secretion and energy metabolism. If endocannabinoids also modulate the responses of pancreatic and intestinal sweet receptors, the findings may open doors to the development of novel therapeutic compounds to combat metabolic diseases such as obesity and diabetes."

Last year, another study found that THC induced cancer cells to kill themselves through autophagy, or self-digestion. As more than one commenter gleefully observed, marijuana gives even cancer the munchies.

Lisa Bramen | | READ MORE

Lisa Bramen was a frequent contributor to Smithsonian.com's Food and Think blog. She is based in northern New York and is also an associate editor at Adirondack Life magazine.