According to folk wisdom, a little spicy kick to the palate before bed can lead to fitful sleep, or even nightmares. And research has confirmed over the years that a spicy meal at night can indeed lead to poor sleep.
The most direct study to show this involved a group of young, healthy men who consumed meals that contained Tabasco sauce and mustard shortly before they turned in on some evenings, and nonspiced control meals on other evenings.
On the nights that included spicy meals, there were marked changes in the subjects’ sleep patterns. They spent less time in both the light phase of sleep known as Stage 2 and the deep, slow-wave Stages 3 and 4.
Several factors may account for the effect. One interesting fact is that, after eating the spicy meals, the subjects had elevated body temperatures during their first sleep cycles. This has been linked in other studies to poorer sleep quality.