The effects of diet on sleep quality in trained athletes Original paper

Many athletes report poor sleep, especially during phases of intense training.^[1] Because sleep is critical for optimal recovery and performance, improving sleep quality is among the most effective strategies for improving an athlete’s competitive advantage. Can diet help improve an athlete's sleep quality?

This systematic review of 35 studies (21 clinical trials, 4 prospective cohort studies, and 10 cross-sectional surveys) examined the effects of diet and dietary factors on sleep quality in trained athletes. The researchers only included studies with athletically trained adult participants who exercised at least 3 times per week and at least 5 hours per week. The participants were mostly male athletes; 17 studies recruited male athletes only, 8 studies recruited female athletes only, and 10 studies recruited both male and female athletes.

The dietary factors included caffeine use, juice consumption, probiotic supplementation, and macronutrient consumption (protein, fats, and carbohydrates). The researchers also assessed the times at which the athletes consumed these dietary factors.

To assess the effects of dietary factors on sleep quality, the researchers evaluated sleep parameters such as sleep duration (hours slept), sleep latency (the time it takes to fall asleep), sleep efficiency (the ratio of time spent asleep versus time spent awake in bed), and wake after sleep onset (time spent awake after having initially fallen asleep). As such, approximately half of the included studies measured sleep quality objectively.

Caffeine intake in the evening had negative effects on sleep quality by decreasing sleep duration and sleep efficiency and increasing sleep latency and wake after sleep onset. In contrast, evening consumption of protein high in tryptophan and carbohydrates high in glycemic index had positive effects on sleep quality, as shown by a reduction in sleep latency.

There was no clear evidence that dietary factors such as probiotics, cherry juice, and beetroot juice improved sleep quality in athletes.

For the overall quality of the evidence, most studies were of high quality (21 studies) and moderate quality (13 studies) with only 1 study of low quality.

Based on these results, the researchers recommend the following practical tips for athletes to improve their sleep quality:

• Limit caffeine consumption to morning, midday, and afternoon.
• Avoid caffeine consumption prior to evening exercise or competitions.
• Supplement with protein high in tryptophan (e.g., whey protein or alpha-lactalbumin) or eat protein sources rich in tryptophan (e.g., eggs, fish, milk, red meat, chickpeas, and almonds) during the evening hours.
• Consume carbohydrates with high glycemic indices immediately after evening exercise.