I just think it has something to do with the bacteria but I don't know how it works. I think that by personal experience certain kind of food causes nightmares.

I just think it has something to do with the bacteria but I don't know how it works. I think that by personal experience certain kind of food causes nightmares. I associate nightmares with food that cause bloating like starch. And also cheese and dairy and fermented food. But I did not try a scientific study by eating for instance dairy and note if I had nightmares. As you say it is most probably related to good and bad bacteria. Also, let's not forget that during sleep consciousness is asleep and if there is a danger the microbes may need to wake up the consciousness and one way of doing this is serve nightmares to the consciousness. I believe that there is a complex relationship with the gut microbes and the consciousness and we don't know how this works.