The relationship between diet and sleep is bidirectional and clinically significant. A cross-sectional study of over 4,500 adults published in the Journal of Clinical Sleep Medicine found that higher dietary quality scores were independently associated with better sleep quality, shorter sleep onset latency, fewer nocturnal awakenings, and better sleep efficiency. The associations held after adjusting for physical activity, mental health status, and other confounders.
Foods That Impair Sleep
- High glycaemic index foods eaten in the evening: produce a glucose spike followed by a drop that triggers cortisol release and can cause nocturnal awakening
- Alcohol: reduces slow-wave and REM sleep even when it initially aids sleep onset; total sleep quality is significantly worse with pre-bed alcohol
- Caffeine after midday: half-life of caffeine is 5 to 7 hours, meaning afternoon coffee is still partially active at midnight
- Large high-fat meals within 3 hours of sleep: delay gastric emptying and can cause reflux that disrupts sleep
- High-sodium foods in the evening: increase nocturnal urination frequency
Foods That Support Sleep
Tryptophan is the amino acid precursor to serotonin and melatonin. Foods rich in tryptophan include turkey, chicken, eggs, cheese, nuts, and seeds. Magnesium-rich foods including dark leafy greens, pumpkin seeds, and dark chocolate support GABA receptor function and sleep onset. Tart cherries contain naturally occurring melatonin and have been shown in clinical trials to improve sleep duration and quality. Kiwi fruit contains serotonin and has evidence for improving sleep onset and total sleep time in middle-aged adults with sleep complaints.
Meal Timing and Sleep Architecture
Eating within a consistent daily window, particularly avoiding eating in the three hours before sleep, is associated with improved sleep quality independent of what is eaten. The digestive system requires energy to process food, and eating close to sleep onset diverts physiological resources away from the repair processes that sleep is supposed to facilitate.