The neurotransmitter serotonin is a powerful and sometimes misunderstood molecule. It is secreted from a tiny percentage of neurons in the brain, yet it controls mood, appetite, grooming, and even violent behavior and suicidal tendencies. 

I’ve discussed it before in the following articles: Sunlight, Sugar, and Serotonin and The Anger Drink. There is more pertinent information at the Dopamine Primer. Everyone who ever saw the famous zoloft commercial back in the day has seen the monoamine theory of depression in action…a theory that is certainly not the entire story. Low serotonin levels in the central nervous system aren’t, actually, associated with depression per se, but low levels are associated with violent behavior, including suicide. It is more accurate to think of serotonin as a groomed and fed and cozy and satiated chemical signal rather than an anti-depressive chemical. What is amazing about serotonin is that monkeying around with the levels via diet can so acutely affect mood and behavior.

In The Anger Drink, a beverage designed to rapidly deplete the central nervous system of serotonin immediately led to more irritable behavior. In a more recent study*, a drink designed to raise levels of serotonin in the brain led to immediate increases in interpersonal trusting behaviors

Mutual trust, ie expecting others to behave as you might, is essential to mutual cooperation and a cornerstone of civilization as we know it. The neurotransmitter serotonin is known to promote mutual cooperation among rats and humans both.

In the new paper, 40 healthy people were given either  tryptophan supplement or neutral control. The tryptophan supplement will very rapidly increase the levels of serotonin the brain, as tryptophan is the dietary precursor to serotonin. An hour after receiving the supplement or placebo, the participants engaged in a mutual trust activity, a game where folks could endow money upon others based on how trustworthy they seemed to be. In this game, five pounds are given to the initial person, who may transfer any percentage of that to another person, whereupon the amount would be multiplied by three, and some or all of this amount could be transferred back to the giver. Therefore the act of transferring money indicates mutual trust. The recipients of the tryptophan drink were statistically more likely to endow more money in the trust game than the recipients of the placebo (and average of 3.57 pounds of 5 pounds possible compared to 1.33 pounds in the placebo group).

It’s a fascinating finding. That a relatively simply dietary manipulation could so readily affect human behavior in an hour’s time. Serotonin and glucose levels are both very readily affected by daily diet. How does the morning special K and skim milk affect behavior as opposed to a protein shake, sugary lowfat vitamin-enriched Slim-Fast, or bacon, hash browns, and eggs? My bias is that our brains are designed to handle vegetables, meat, eggs, fruit, seafood, and nuts, and not meant to handle processed foods, candy, alcohol, and any number of modern conveniences. We are very likely to point to whiskey as a behavior modifier, not so much the morning cereal or azo food dyes and sugar in the pop tarts or fruit roll-ups. I would err on the side of caution, and maybe do some home experiments of your own with real food and eschewing processed foods for a time. Who knows what the results could be?  

*Thanks to Dallas Hartwig for the link.

Image credit

Copyright Emily Deans, MD

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