In a Chocolate-y Mood?
Do you ever have a strong craving for chocolate? Have you experienced an increase in these cravings in recent weeks, possibly induced by advertisements?
I certainly have fallen to impulse-buys at the front of the grocery store in order to fulfill my cravings for the darkest of dark chocolate. They put those rows and rows of chocolate next to the checkout stand on purpose: to make it easier for you to impulsively buy something you want, but don’t necessarily need. I don’t need the chocolate, but that first bite so rich and delicious fills me with feelings of joy and satisfaction. Naturally, we would ask, what is happening in the brain?
Chocolate contains several ingredients that could potentially alter our mood and behavior. Fat, sugar, butter, oils, cocoa, cocoa butter, and whatever else you see on the nutrition label make up the delicious dark solid we call chocolate. Scientific studies have focused on the following compounds found in the cocoa bean: flavanols, caffeine, and theobromine (similar to caffeine in both chemical structure and effects – for difference in molecular structure see http://www.themolecularuniverse.com/blog/archives/2008/12/27/caffeine_and_theobromine/). Scientists looked at these ingredients individually and in various combinations to figure out what exactly contributes to brain changes after eating chocolate.
Smit et al.  hypothesized that caffeine and theobromine are specifically the ingredients of chocolate that produce elevations in mood and performance in thinking tasks. To test this they used pills representing contents of a 50-gram bar of dark chocolate. They used pills with three different contents: 11.6g of Cadbury’s Bournville cocoa powder, 250mg theobromine plus 19mg caffeine, and a placebo pill. Subjects took one of these three pills. The cognitive measures they used were a simple reaction time task, the Thurstone tapping task (measures finger dexterity and motor speed), and a rapid visual information processing task. Performance improved on all cognitive measures and mood survey measures for the cocoa group and the caffeine plus theobromine group. Because improvements were the same for both groups, the authors determined that the caffeine and theobromine in the chocolate are responsible for elevations in mood and cognitive performance.
Other studies found similar cognitive enhancement and mood elevations using various measures. Furthermore, Smit et al. found a dose-response effect for pills containing caffeine plus theobromine on the simple reaction time task and the rapid visual information processing task . This means that at higher concentrations of caffeine and theobromine, they saw see bigger improvements in task performance. These enhancement effects were generally seen two hours after ingestion. So the next time you eat some chocolate, just think of all that caffeine and theobromine pumping through your system, improving mood and some cognitive function. (However, your habitual coffee break may increase or diminish these cognitive gains depending on your caffeine intake .)
Studies also focus on flavanols or flavonoids, which have been shown to enhance cognitive function and offer neuroprotection when taken long-term [3-5]. Flavanoids are in other foods like tea, red wine, and apples. Francis et al.  looked at how a drink containing either low or high concentrations of cocoa flavanols affected brain activation and cognitive function using functional magnetic resonance imaging (fMRI), cerebral blood flow measurements, and a task that required quick attention. Subjects were trained on the task before any fMRI scans in order to see effects from flavanols after the task had already been learned. Subjects had the drink for 5 days, and on the fifth day they were tested in the scanner. Measurements were taken before drink consumption (baseline measurements) and 2, 4, and 6 hours after drink consumption.
Here’s the task: Subjects were presented with a letter paired with a number. The color of the font indicated whether the subject should pay attention to the letter or the number. The subject then had to press the left button for a vowel or odd number, and press the right button for a consonant or even number. The subjects who received the drink with cocoa flavanols showed increased blood flow and activation in cortical areas of the brain (dorsolateral prefrontal cortex, anterior cingulate cortex, and parietal cortex, see figure below) compared to baseline measurements. However, they did not improve task performance. So there are some changes in brain blood flow after drinking the flavanols, and maybe the authors just needed to look at a different task that is affected by those changes in brain activation.
Field et al.  looked at cognitive assessments that are more likely to be affected by changes in blood flow: contrast sensitivity (stating when you cannot distinguish between brightness of two images) and motion coherence threshold (the smallest ratio of dots that you can see moving in the same direction in a field of randomly moving dots). Subjects either ate 35 g of the dark chocolate (773 mg flavanols, 38 mg caffeine, and 222mg theobromine) or 35 g of white chocolate (only trace amounts of flavanols, caffeine, and theobromine). So it is possible that whatever effects they saw may also be due to differences between caffeine and theobromine content. Subjects that had a high concentration of cocoa flavanols showed improvements in contrast sensitivity and motion coherence threshold compared to controls who ate white chocolate. The same cocoa flavanols subjects were also significantly more accurate in a spatial working memory tasks in which they had to remember the location of objects on a screen. So if you’re lost or can’t remember where you parked your car, eat more chocolate? Maybe. At least you might be less bummed about getting lost.
The short conclusion: Eating chocolate can improve some cognitive processes and elevate mood.
The slightly-less-short conclusion: After looking at several of these studies, I feel safe to say I will continue to eat chocolate. I might even eat it to make myself happier. And what about chocolate as a Valentine’s day gift? I would say go for it! Chances are the chocolate will make that special someone slightly happier, increase cortical cerebral blood flow, and quicken some reaction times. Just wait two hours to see those awesome brain effects.
 Smit HJ, Gaffan EA, Rogers PJ. Methylxanthines are the psycho- pharmacologically active constituents of chocolate. Psychopharmacology (Berl). 2004;176:412–419.
 Attwood, A. S., S. Higgs, and P. Terry. “Differential responsiveness to caffeine and perceived effects of caffeine in moderate and high regular caffeine consumers.” Psychopharmacology 2007;190.4: 469-477.
Spencer JPE. Flavonoids: modulators of brain function? Br J Nutr. 2008;99(E Suppl 1):ES60–ES77.
 Letenneur L, Proust-Lima C, Le Gouge A, et al. Flavonoid intake and cognitive decline over a 10-year period. Am J Epidemiol. 2007;165:1364–1371.
 Patel AK, Rogers JT, Huang X. Flavanols, mild cognitive impairment, and Alzheimer’s dementia. Int J Clin Exp Med. 2008;1:181–191.
 Commenges D, Scotet V, Renaud S, et al. Intake of flavonoids and risk of demen- tia. Eur J Epidemiol. 2000;16:357–363
 Francis S, Head K, Morris PG, et al. The effect of flavanol-rich cocoa on the fMRI response to a cognitive task in healthy young people. J Cardiovasc Pharmacol. 2006;47(Suppl 2):S215–S220
 Field DT, Williams CM, Butler LT. Consumption of cocoa flavanols results in an acute improvement in visual and cognitive functions. Physiol Behav. 2011;103:255–260.
chocolate image from http://www.livingwithlibby.com/wp-content/uploads/2011/09/chocolate_i-stock.jpg
chocolate brain image from http://laughingsquid.com/wp-content/uploads/chocolate.jpg