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Chocolate, anyone? Happy Valentine’s Day…

Rosemary Joyce, professor of anthropology | February 13, 2010

Tomorrow is Valentine’s Day, which for many people means chocolate.  A 2009 article from the Nielsen company, a market research firm, predicted that sales of chocolate for Valentine’s Day would reach $345 million, to purchase 58 million pounds of chocolate, which they estimated would be over 5% of chocolate sales for the year. Chocolate takes center stage for this holiday about love because it makes people feel good.

And increasingly, we are told, chocolate does more than make you feel good; it can help keep you healthy. Research published this past January by an international team, including chemists from UC Davis, found that epicatechin– a flavonol in chocolate– improved circulation of the blood. Chocolate is believed to have antioxidant effects. Harvard Medical School published an overview of studies of these and other possible medical benefits of chocolate, including improving blood pressure and insulin sensitivity and aiding blood clotting. The highest health benefits of chocolate come from the least processed form, dark chocolate.

Chocolate chemistry is complex, but among the suite of chemicals it contains are traces of anandamide, a chemical that binds to the same receptors in the brain that respond to cannabinoids– the active chemicals in marijuana. Also present is tryptophan, which leads to the production of serotonin, a neurotransmitter that improves mood and encourages relaxation. Chocolate contains low concentrations of phenylethylamine, an amphetamine-like chemical linked to the release of dopamine. Another similar chemical in chocolate is tyramine. Finally, eating chocolate triggers the release of endorphins in the brain, leading to feelings of well-being. Most of these chemicals are found in very low concentration, but they are remarkably consistent in their biological effects with the good feelings chocolate lovers ascribe to their drug of choice.

But it’s another chemical component of chocolate that I am most concerned with in my research: Theobromine. Named after the genus of the plant that is the source for chocolate, Theobroma cacao (“cacao, food of the gods”) is a methylxanthine, related to caffeine (which is also present in the cacao plant).

Theobromine is the key to identifying cacao residues in archaeological sites in the Americas where the cacao plant (or its similarly used relative, Theobroma bicolor) was in use outside the natural range of related plants (found in northern South America). By using water, alcohol, and even chloroform to dissolve chemicals deposited in the porous walls of pottery suspected of having been used to hold cacao, and subjecting the extracts to chemical analysis, we can tell when an empty bowl, bottle, or drinking cup once contained chocolate.

When we published our results of analysis of our first set of sherds from Puerto Escondido in northern Honduras in 2007 in the Proceedings of the National Academy of Science, our 1150 BC date for one sample pushed the earliest known dates for cacao back by more than 500 years.  Not long after, another research team reported even earlier samples from sites in Mexico. There is every reason to expect that new analyses of very early pottery excavated throughout Mexico and Central America will give us evidence of early chocolate in many different areas between 2000 and 1000 BC.

There are other chocolate discoveries still to be made. In early 2009, archaeologist Patricia Crown published her analysis of residues from tall cups found in Chaco Canyon, in New Mexico– far north of the area where the cacao plant grows, and far from the nearest known centers of cacao use. And amazingly, tests confirmed that even here, cacao was being consumed– over 1200 miles north of the closest Mexican cacao plantations.

So happy Valentine’s Day; and when you share chocolate with your loved one, think about the untold stories of chocolate that archaeologists, medical researchers, and chemists are working to sketch out.