Gary Wenk explains why certain chemicals inside plants can affect the way we act and think because plants evolved alongside humans.
I didn’t expect him to end off his thesis in such a humorous way though:
Every spaceman from Flash Gordon to Captain Kirk to Luke Skywalker should feel safe walking around any planet (except their own) with impunity from animal and plant toxins. For this same reason, the intoxicating drinks and powerful medicines that always seem to be popular in these foreign worlds in science fiction movies would also have totally different effects, if any effects at all, on the brains of our plucky spaceman. Eating otherworldly foods might be the most disappointing and distressing experience of all: Even if they were filling and somehow tasted delicious, as products of utterly alien biochemistries they would probably prove devoid of nourishment for our Earthly bodies. Thus, starvation might be the greatest threat to any future explorers of alien biospheres. Unless, perhaps, they’d brought along a large supply of chocolate.