Sleep and nutrition in athletes

Sleep and nutrition in athletes is an often overlooked aspect of recovery and performance. In this article, we explore the multiple factors that can affect an athlete’s sleep quality and quantity.

Sleep in athletes

Many athletes suffer from sleep issues, including short duration of sleep (a.k.a. sleep deprivation) and sleep disturbances (e.g. insomnia, waking up at night) (1, 2).

The factors that may contribute to sleep issues in athletes include:

• Muscle soreness (1) and pain
• Intense training (1)
• Early or late training sessions or competition (2, 3, 4)
• Poor sleep hygiene, including screen use close to bedtime (2, 3)
• Stress, nerves and/or anxiety due to competition or other reasons (2, 3)
• Caffeine intake (3), especially in the several hours before bedtime
• Travel across different time zones (2, 4), especially when travelling East to West (2)

How can sleep affect athletes?

Sleep deprivation

Long bouts (24-64 hours) of sleep deprivation have been shown to reduce specific measures of performance such as vertical jump, knee extension strength, endurance running and sprint performance (3).

Shorter sleep deprivation (i.e. a few hours per night) can negatively affect mood and some strength exercises such as bench press, leg press and deadlifts (3).

In addition, sleep deprivation can negatively impact cognitive processes, including attention, concentration, memory and decision-making, which are important in many sports (2, 3).

There is also a bilateral relationship between pain and sleep deprivation (3).

Acute sleep deprivation can impair the immune response, increasing the chance of infections. Sleep disturbance can increase inflammation (1, 3).

Chronic sleep loss can negatively impact glucose metabolism and the secretion of hormones that regular appetite, resulting in increased risk of obesity and diabetes (1, 2, 3). In addition, glucose metabolism also affects glycogen synthesis, which is important for some types of exercise (1).

Sleep deprivation can also affect the secretion of hormones that have a role in protein synthesis (i.e. an increase in catabolic hormones and a decrease in anabolic hormones). This results in impaired recovery, training adaptations (1, 3) and body composition.

Extra sleep

When athletes are allowed to sleep in, they report increased performance in sprints, reaction time, gross motor skills, cognitive performance, and mood (2, 3, 4).

Naps

Similar to prolonged sleep, napping has also been shown to improve sprint performance, alertness and cognitive tasks (2, 3).

Sleep and nutrition in athletes

Some of the nutritional factors that can affect sleep include:

Carbohydrate

Carbohydrate intake can increase the amount of the amino acid tryptophan (Trp) and, therefore, affect the ratio of Trp to large neutral amino acids (LNAA). See the section Tryptophan below to understand why this is important (1, 3).

There is some evidence that high glycaemic index (GI) meals are more effective in improving sleep, as measured by reduced the time it takes to fall asleep, increased rapid eye movement (REM or deep) sleep and decreased light sleep (1, 3). Optimal timing seems to be 4-1 hours before bedtime. It also seems that carbohydrate-containing solid meals work better than liquid meals (3).

Protein and fat

There is mixed evidence when it comes to protein intake, for example, high protein diets have been linked to increased restlessness but also less waking-up episodes. High fat intake has been linked to decreased sleep time (3).

Energy

Most people who has gone to bed slightly hungry have experienced how hard it is to fall or stay asleep. There is very little scientific evidence to prove this observation but it seems plausible that low energy intake can disrupt sleep (3).

Melatonin

Melatonin is a hormone that induces sleep (1, 3). There are several factors that affect the production of melatonin, including exposure to blue light in the eyes.

Low doses of melatonin (0.3 mg) can induce sleep in individuals who have problems falling asleep (1).

Tryptophan

The ratio of Trp to LNAAs facilitates the transport of Trp into the brain, where it can be used to produce serotonin and 5-H5 (neurotransmitters involved in the sleep-wake cycle), and melatonin (1, 3).

Foods rich in Trp include milk, turkey (perhaps the most famous source of Trp in the US due to Thanksgiving), chicken, fish, eggs, pumpkin seeds, beans, peanuts, cheese, leafy greens, and whey protein enriched with α-lactalbumin (1).

Antioxidants

In theory, the intake of antioxidant compounds such as vitamins A, C and E, can influence sleep due to their capacity to improve recovery from exercise (1).

It is important to note that inflammation is an important component of both training adaptations and recovery from injury, so blunting the inflammatory process by antioxidant supplementation is not always desirable.

Tart cherry juice

Tart cherry juice can be effective in improving quantity and quality of sleep due to its content of melatonin and phenolic compounds which have antioxidant and anti-inflammatory roles. Tart cherry juice is a supplement commonly used for exercise recovery and delayed-onset muscle soreness (DOMs). Better recovery usually translates to better sleep (1, 3).

Kiwifruit

Kiwifruit contains serotonin and several antioxidant compounds including vitamins C, E and beta-carotene. Documented protocols include 2 kiwifruit eaten 1 hour before sleep (1).

Kiwifruit can also alleviate constipation, therefore it can be beneficial for athletes with this issue.

B vitamins

Vitamins B3 (niacin), B6 (pyridoxine), B9 (folate) and B12 are involved in melatonin secretion and the metabolism of Trp, including its conversion into serotonin (1).

Magnesium

Magnesium is a popular supplement used to facilitate sleep. The mechanisms behind this action seem to be its ability to enhance the secretion of melatonin and to act as a GABA (an inhibitory neurotransmitter) agonist (1).

Valerian

Valerian is a herb known for its calming effects. There is not a lot of hard evidence pointing to its ability to improve sleep, but there are subjective accounts that valerian can improve sleep (3).

Glycine

Similar to valerian, glycine can also improve subjective ratings of sleep (3).

Summary and recommendations

Sleep deprivation can negatively affect many aspects of health, exercise performance and recovery.

Athletes are susceptible to experiencing sleep disturbances due to their training and competition schedules, travel, stress, and other causes.

Besides practising good sleep hygiene, athletes can employ nutritional strategies such as avoiding caffeine intake too close to bedtime, eating a meal containing high GI carbohydrate and/or foods rich in Trp. In addition, athletes who have issues sleeping due to impaired recovery or DOMs can try antioxidant-rich foods (e.g. tart cherry juice, kiwifruit) or supplements.

References

1. Doherty R, Madigan S, Warrington G, Ellis J. Sleep and Nutrition Interactions: Implications for Athletes. Nutrients. 2019/04/14. 2019;11(4).
2. Vitale KC, Owens R, Hopkins SR, Malhotra A. Sleep Hygiene for Optimizing Recovery in Athletes: Review and Recommendations. Int J Sport Med. 2019/07/10. 2019;40(8):535–43.
3. Halson SL. Sleep in elite athletes and nutritional interventions to enhance sleep. Sport Med. 2014/05/06. 2014;44 Suppl 1(Suppl 1):S13-23.
4. Knufinke M, Nieuwenhuys A, Maase K, Moen MH, Geurts SAE, Coenen AML, et al. Effects of Natural Between-Days Variation in Sleep on Elite Athletes’ Psychomotor Vigilance and Sport-Specific Measures of Performance. J Sport Sci Med. 2018/11/28. 2018;17(4):515–24.

[Photo by Shane on Unsplash]

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