You may be an undigested bit of beef, a blot of mustard, a crumb of cheese, a fragment of underdone potato. There’s more of gravy than of grave about you, whatever you are!
-- Scrooge to Marley’s ghost; from Charles Dickens’ A Christmas Carol
Was it something I ate?
Anyone who has ever gone to bed after a dinner of enchiladas can tell you that what you eat affects your dreams. Surprisingly, there is very little solid science to explain it.
Spicy foods in particular are notorious for inspiring especially vivid dreams.
Some in the medical community have theorized that the heat from the spices elevates body temperature enough to interfere with the quality of sleep. The discomfort then works its way into your subconscious, and is reflected in the narrative it creates. Real life stomach aches and other types of gastric distress can end up as dream-pain experienced by your dream-self.
Another theory suggests that what you eat before bedtime isn’t as important as how much you eat and when you eat it. Any digestion increases the metabolism and brain activity, so the more you eat and the closer it is to bedtime, the more vivid the dreams.
Sweet dreams: Low blood sugar, or hypoglycemia, is another culprit. When your body’s blood sugar level is low, which happens when you haven’t eaten in a long while before bedtime, your brain gives you a little spurt of adrenaline that causes your body to drop some stored glucose into the bloodstream. If you’ve ever had a dream that wasn’t just vivid but also felt especially frantic, you know the feeling of adrenalized dreaming.
If you’ve ever dreamed you were sitting in a restaurant only to wake up and find your partner cooking up some bacon, you already know that food smells can creep into your dreams. The sense of smell is associated with the part of the brain that is associated with emotions, so food smells can take on a literal meaning and also affect the mood of your sleeping-self. One study (unpublished but presented to the American Academy of Otolarygology) pumped different scents into the nostrils of sleeping subjects, and found that dream moods and impressions were clearly colored by the smells, although dream content seemed unchanged.
Gaming your own dreams
We know that food affects dreams, but no one has figured out how to use it to manipulate the content of dreams, Inception-style. The best we can do is choose foods and time our meals to get the best night’s sleep possible. Web MD has a slide show of foods that help and foods that harm your sleep.