It's that time of year again: The pumpkins are carved, the costumes are all laid out with care, and taking candy from strangers is not only allowed, it's encouraged. But, with all the focus on the tastebuds, just what happens in your brain when you're eating candy?
The Secret Ingredient is Sugar (Also, Dopamine)
When you sink your teeth into that first bite of chocolate and caramel, the sweetness and the texture might be at the front of your mind, but that's not all that's happening. Reward and pleasure signals in the brain are also being triggered. The star of the show is dopamine, the little neurotransmitter that could, associated with pleasure from everything from food to music to runner's high. So far, so good. But what happens when a little bit of sugar turns into a lot? Strange doings, it turns out.
Just how the brain responds to sugar and fat can change over time. A study from Brookhaven National Laboratory found that as obesity increased, the response in dopamine receptors was lowered. Another study in the Journal of Nutrition offered rats access to sugar, only to yank it away shortly later. What they found were changes not only in their behavior, but also in their neurochemical levels, especially those associated with pleasure and addiction — dopamine again, but also opioids. Nicole Avena, one of the authors on the study, told io9: "In rats, overeating of sugar can produce signs of tolerance, withdrawal and craving, which are coupled with changes in the reward-related brains systems that include alterations in dopamine and opioids."
Hazy Memories of Candy Gone-by
But it's not just rewards; a study published by UCLA researchers in the Journal of Physiology found that rats with high-fructose diets had trouble completing a previously learned maze. Fortunately, they also found that the effects were counteracted with the addition of eating some omega-3s. (Free candy idea for any potential Willy Wonkas out there: chocolate-covered salmon. No, no, please! No need to thank me.) And the news isn't all bad for candy and memory. A recent study published in Neurology found that amongst older people with impaired blood flow, two cups of cocoa a day not only increased blood flow to the brain, it also improved skills in short-term memory.
Yes, Actually, I Can Believe It's Not Sugar
Of course, there's no shortage of sugar-substitutes or people searching for a new one. Scientific American shares this charming (and also alarming) anecdote about a grad student who was told by his adviser to "test" an artificial sweetening compound they were developing and instead heard that his adviser wanted him to "taste" the compound. The result of this particular game of Scientific Telephone (coming soon to a toy store near you, if my imagination has anything to say about it) was not, as one might imagine, either instantaneous death or the slow dawning of a mutant tasting-ability, offering equal parts great power and great responsibility. Instead, it was only a sweet, pleasant-enough taste that we now know as Splenda.
But even if artificial sweeteners are able to capture some of the sweetness of sugar, they can't capture its weird physiological properties, at least as far as the brain is concerned. A study published last year in the Journal of Physiology by researchers at Yale offered mice treats sweetened with sugar and treats sweetened artificially, but it was only with sugar that they saw a jump in dopamine levels.
Researchers also noted that when given the choice between the two, the hungry (and, apparently, quite discerning) mice went with real sugar over the artificial stuff -— even when the artificial stuff tasted sweeter.