Introduction

According to the Mayo Clinic, a nightmare is a perturbing dream that is associated with negative feelings. When these nightmares become frequent, disrupted sleep can impair daily functioning or cause a fear of sleeping; they may indicate a condition known as nightmare disorder.

The importance of sleep quality to overall health is often underestimated. Appropriate sleep promotes growth, helps heart health, supports weight management and can help keep the immune system strong, among other benefits. However, sleep is not only about the quantity you get, but also about the quality of sleep and how rested you feel when you wake up.¹

To achieve a restful sleep, it's recommended to avoid late-night snacking, sugar, caffeine and alcohol before bedtime. These insights point to a diet-sleep connection, suggesting that certain dietary elements can either hinder or enhance sleep quality.^1,2 

In this article, we will explore how dietary choices can influence not only overall sleep quality but also may influence the occurrence of nightmares.

Understanding nightmare disorder

Nightmare disorder, along with recurrent isolated sleep paralysis, falls under the category of rapid eye movement (REM) sleep parasomnias. These disturbances can lead to significant emotional distress, and nightmare disorder is particularly prevalent in individuals with psychiatric conditions and post-traumatic stress disorder. Diagnostic criteria for nightmare disorder consist of repeated occurrences of extended, extremely dysphoric, and well-remembered dreams that usually involve threats to survival, security or physical integrity; moreover, these episodes must occur at least once per week. After waking, individuals are rapidly oriented and alert, which can make it harder to fall asleep, therefore contributing to sleep disruption. Over time, this can result in persistent daytime fatigue and even sleep-related anxiety, further impacting overall well-being.³

How does diet affect sleep and dream patterns?

A study conducted in 2015 explored the idea that food can influence people's dreams. The study found two distinct relationships between food and dreaming. One links disturbing dreams to a set of problematic behaviours and traits, including disordered sleep, dieting, binge eating, emotional eating, and poor hunger regulation, suggesting a pathological pattern not solely explained by sleep issues. The other connects pleasant, vivid dreams to wellness indicators, such as better sleep, healthier diets, longer fasting periods, and less uncontrolled eating, showing that these positive dream experiences are also not solely due to sleep quality.⁴

General impact of food on sleep cycles

Emerging research indicates that dietary quality, energy intake and food types can affect sleep quality and patterns. The field of chrono-nutrition is a field of study in which the role of food intake and metabolism has been studied.⁵

The NHANES, a cross-sectional study, explored the association of meal timing with sleep quality, providing new evidence of dietary behaviour and its relationship with sleep quality. This study mainly found that later meal timing was correlated with a score indicating poorer sleep quality.⁶

Moreover, blood sugar levels could also influence sleep quality and nightmares, such is the example of a case report in a diabetic patient who developed recurrent nightmares within a week of starting metformin treatment, a common treatment to control type 2 diabetes. The sudden onset and disappearance of nightmares after metformin initiation and discontinuation made it the primary cause of his nightmares. This is one case study, and the relationship of metformin remains a subject of research. However, it is an example in which, not directly diet, but blood glucose levels led to nightmare development in a patient.⁷

Nutrients that promote healthy sleep

Certain foods are known to encourage better sleep. Consuming a high-protein diet with essential amino acids, which are molecules that help to build proteins, low-glycaemic index foods, and certain fruits rich in antioxidants can promote a better night’s sleep. Melatonin is a hormone that plays a role in sleep onset and has been identified in foods including meat, mushrooms, pineapple, oranges and bananas, and can also be found as an over-the-counter supplement. Moreover, foods that are sources of serotonin can also promote better sleep without disturbances. On the other hand, tryptophan is an amino acid that can also assist in improving sleep.² 

In healthy individuals, carbohydrates in the diet can also influence sleep quality. For example, in Japan, a study made with middle-aged women found that consuming foods with a high glycaemic index and a lack of vegetables in the diet had a poor sleep quality.⁸ 

Nutrients and foods that may disrupt sleep

Conversely, other nutritional elements can have a role in impairing sleep. Not surprisingly, caffeine, found in coffee, tea and other drinks, increases alertness and counteracts fatigue and sleep. The stimulatory effects of coffee can interfere with sleep for some people, due to a decrease in melatonin, which consequently decreases the sleep quality. However, this effect is not seen in everyone, and there is also a dose-dependent relationship between caffeine intake and sleep disruption.² 

Other stimulants include nicotine, found in tobacco products, and alcohol consumption, which can lead to sleep disruption and poor sleep quality if consumed within hours of bedtime. Additionally, foods that cause acid reflux, such as fried or spicy foods, can trigger nighttime awakenings and poor sleep quality.² 

Research and case studies

Research on the relationship between diet and sleep continues to grow. A study conducted in children showed that they were reflecting shorter nighttime sleep and later sleep onset, associated with more frequent soda consumption. Moreover, shorter nighttime and sleep durations were associated with more frequent consumption of fast food. Based on the findings of this study, the frequent consumption of less nutritious food is more strongly linked to poorer sleep outcomes.⁹

Another study was made in college students, some of them with poor sleep quality. Their dietary patterns were analysed using a dietary inflammatory score, and a direct significant association was found between a pro-inflammatory diet and increased day dysfunction due to sleep disturbance.¹⁰ 

Despite specific case reports that have found links between certain food habits that can induce nightmare disorder, broader scientific evidence remains limited due to small sample sizes and variability in study design.

Dietary habits that may reduce nightmares

Establishing certain habits can support a healthy sleep routine, such as sticking to a consistent schedule and creating a comfortable sleep environment. The NHS notes that maintaining a balanced diet and engaging in regular physical activity can promote relaxation and improve sleep quality. It's also recommended to avoid heavy meals shortly before bed, and to steer clear of caffeine, alcohol, or nicotine in the hour or two leading up to sleep. When it comes to exercise, it's best to avoid vigorous activity within 90 minutes of going to bed.^1,2 

There is a need for rigorous research in real-life settings to truly comprehend not only the role of diet in nightmare disorder, but also the possibility of improving sleep quality through diet, in a comparable way that is achieved through meditation.¹¹

Summary

There is a clear, yet complex, connection between diet and sleep. Research highlights a bidirectional relationship with sleep and health, in which food affects sleep quality, and sleep patterns influence dietary choices.

Chrono-nutrition studies play an important role in understanding how diets rich in certain nutrients can improve sleep. Moreover, weight loss can also help improve sleep outcomes, and removing the consumption of stimulants from our diet can have an impactful effect on sleep quality, potentially reducing the occurrence of nightmares.

While making dietary adjustments can be helpful, those experiencing nightmare disorder should consult a medical professional to explore any underlying causes beyond diet. Before making significant changes to your eating habits for sleep improvement, professional guidance is recommended.