Although some late-night snacks may aid sleep, it's probably more important to avoid unhealthy foods before bedtime. Studies have correlated higher fibre intake with longer periods of deep sleep and fewer nighttime wake-ups. Poor sleep can disrupt the gut microbiome, which can then lead to further negative sleep effects. But a high intake of these ultra-processed foods – with high sugar levels and low levels of fibre – in turn appears to lead to poorer sleep quality. For example, a study of students in Saudi Arabia reported a “significant association” between their sugar intake and getting poor sleep.