Tryptophan saves the day?

This week in the United States we will celebrate Thanksgiving. In addition to feelings of gratitude, family gatherings can also stir up heated arguments about political issues and other differences between family members. Today's meme suggests that the neurotransmitter found in turkey meat, the centerpiece of most Thanksgiving feasts, may be an antidote to this problem:

Tryptophan naturally occurs in turkey meat and other common foods (including beans for vegetarians). Its presence in the brain has been linked to an increase in Serotonin, another neurotransmitter associated with positive mood and decreased aggression. Could eating Tryptophan-rich foods decrease fighting? An experiment with non-human subjects suggests that a touch of Tryptophan might help.

Walz, Stertz, Fijtman, dos Santos, and de Almeida (2013) divided male mice into five groups: four groups received a dose of Tryptophan that was 1%, 2%, 3%, or 10% of 30 ml of a carrier liquid; the last group was the control group so they did not get any Tryptophan in their liquid. Immediately after dosing, the mice were individually exposed to an intruder: a stranger male mouse. This encounter lasted for five minutes as the test mouse's behaviors were recorded. This experience occurred eight times for all male mice from the five groups.

When the animals' reactions were coded across these trials, Walz et al. found that the mice dosed with a 1% and 2% Tryptophan solution were less likely than the control group to aggressively bite or to threaten the stranger mouse from the side. The other doses did not show a significant reduction in these aggressive behaviors, and none of the doses was related to changes in non-aggressive behaviors, such as activity levels or grooming. At a low dose, Tryptophan is speculated to raise Serotonin levels enough to take the edge off this stressful experience; at larger doses it may be that Serotonin rises so high that it sends a feedback signal to the mouse's body to decrease Serotonin production thereby undoing any good effect of supplementation.

The authors concluded, "...that low doses of [Tryptophan] are able to reduce aggressive behavior in male mice....Tryptophan supplementation may be an alternative treatment for aggression in groups that exhibit such behavior" (p. 400). Of course, we can't be sure that the same dose of Tryptophan (especially if it is combined with cranberry sauce, mashed potatoes, and stuffing) would have the same effect on humans or that it would diminish verbal aggression as it did physical aggression. Walz et al. encouraged further research: "To control aggressiveness, a person's diet may be an important factor" (p. 397).

Until then, when discussions get heated at your next family gathering, try changing the subject to something that everyone can agree on. Until we know the details about Tryptophan we will apparently have to rely on Adele.

Further Reading:

The Walz et al. (2013) article is available online and the Psychology and Neuroscience journal article can be accessed through your local college library.

People used to think that the Tryptophan in turkey was responsible for that sleepy feeling so many of us have after the big meal. Find out what is more likely to blame in this Live Science piece by Tanya Lewis.

Why do family celebrations so often turn into family fights? Read Olga Khazan's article in The Atlantic:  "Why families fight during the holidays."