Recently a man tells me (to his amazement!) that he is having nightmares every time he eats lettuce. He has noticed this pattern over a long period of time and is pretty sure that lettuce is the trigger of his nightmares. How could this be? It turns out he has a serious gastrointestinal disorder and lettuce is in fact, a trigger for a painful episode in waking life. His body knows that lettuce is toxic for him. The dream imagery is a mechanism for his body to tell his mind that lettuce is his illness trigger.
Scientific research has shown that foods do not necessarily trigger dreams of any specific theme. That is, chocolate does not ellict sexual imagery and meat does not ellict imagery of aggression. However, if foods are linked to illness-then dream imagery and food will ellicit a warning to the dreamer.
The mind-body connection is one of the most important purposes of dreaming.