Actually according to most papers tryptophan content in rice is rather low. In livestock with rice based diets tryptophan is supplemented. There are GM versions with high tryptophan content around, but I do not think that they are used for human food yet.
Also tryptophan itself is not calming, but serotonin (of which tryptophan is a precursor).
According to Comai et al (International Congress Series Volume 1304, 1 November 2007, Pages 227-232). Rice had the lowest (non-protein) trp concentration.
To have any effect you would have to eat rather enormous amounts of rice and rice cake.
The same is for milk btw. The amount is too low to have any true effect. It is likely that having any drink that relaxes you will have the same effect. And yes, the same is true for turkeys. There are estimations out there that one need gallons of milk and around 30 pounds of turkey to get trp concentrations with any physiological effects.
And that is only if you are able to utilize all that is present in the meat/milk/rice. The bioavailability (the amount that can be actually utilized by your body) is only a fraction thereof. In addition for the sleepiness part only the tiny remaining amount that actually passes the blood-brain barrier will have any effect. This fraction (given that in about any protein containing food trp will have the lowest abundance), is so incredibly low that even those vast amounts underestimate things.
Sounds like urban myths to me, I am afraid.
Edited by CharonY, 28 August 2009 - 08:58 PM.