From belly to brain: The science of Thanksgiving

Photo by Pink Sherbet Pho­tog­raphy via Flickr.

There are cer­tain things most Amer­i­cans expect to encounter on Thursday: Turkey. Mashed pota­toes. A lazy after­noon. Too many lagers. A belly ache. A nod toward the things we’re thankful for.

But the one thing we should per­haps be most thankful for may slip under the radar, and that is the incred­ible human brain, which kicks into high gear on this annual day of indul­gence and gratitude.

In an op-​​ed pub­lished last Sat­urday in The Boston Globe titled Grat­i­tude Pays Big Div­i­dends, psy­chology pro­fessor Dave DeSteno dis­cusses how human emo­tions have evolved to “serve socially adap­tive func­tions.” He says we tend to think of grat­i­tude in terms of the past: the things that have already hap­pened that we’re thankful for now. But in fact, DeSteno argues, grat­i­tude may have more to do with the future.

DeSteno’s lab has shown that people who have recently expe­ri­enced kind­ness from someone else are more likely to pass that kind­ness along to another, even a stranger. “The more grat­i­tude people feel,” he writes, “the more likely it is they’ll help anyone, even if it’s someone they’ve never laid eyes on before.” For that reason, he sees grat­i­tude as a social strategy that helps build resilient com­mu­ni­ties. What goes around really does come around and our brains seem to know it even if we some­times forget it.

On Thanks­giving Day we reflect on our rela­tion­ships and the things we have — both mate­rial and oth­er­wise.. But it doesn’t seem to matter what we’re thankful for — as long as we’re feeling grat­i­tude, we’re more likely to help our fellow humans.

Of course, turkey day isn’t always ter­ribly con­ducive to being helpful — if that help requires a con­sid­er­able amount of phys­ical energy. That’s because it’s all being fun­neled off to do the seem­ingly more impor­tant job (in an evo­lu­tionary sense) of diges­tion. Tryp­to­phan is the amino acid that’s often pegged as the cause for the over­whelming exhaus­tion that sets in after the mas­sive, gravy smoth­ered, turkey dinner we like to indulge in once a year. But, says chem­istry and chem­ical biology pro­fessor and chair Graham Jones, this is a common misconception.

Indeed, while it is true that tryp­to­phan has sleep inducing effects, and its metabo­lites — ser­a­tonin and mela­tonin — are sleep reg­u­la­tors, it does not account for the drowsi­ness we often expe­ri­ence.” He says that drowsi­ness would require eating a heck of a lot more turkey than even the most fer­vent mouth stuffers among us could con­sume: close to 40 pounds worth.

The more likely cul­prits of our food-​​induced coma are the fats and car­bo­hy­drates the meal con­tains, according to Jones. “Car­bo­hy­drates make the pan­creas secrete more insulin, which in turn stim­u­lates pro­duc­tion of sero­tonin,” he explains. “Diges­tion of fats results in redis­tri­b­u­tion of blood flow, also resulting in low­ering of our energy levels and increased seda­tive feeling.” Not to men­tion the beers and the wine and what­ever other bac­cha­na­lian treats you imbibe, which are all cen­tral ner­vous sys­tems depressors.

As you relax after the food tomorrow, it might be a good idea to keep all of this in mind. Even if someone hasn’t recently paid you a kind­ness, you still have quite a bit to be thankful for, as you sit in the Barcalounger, let­ting your neu­ro­trans­mit­ters and your hor­mones and your enzymes work their bot­toms off to deal with your over-​​indulgence. After all, any grat­i­tude you can muster is a pay­ment into society’s future.