Sleep deprivation in athletes and how nutrition can help

As a sport and exercise nutritionist, it’s important for me to take account of an athlete’s stress levels and sleeping habits.

These have a huge impact on inflammation, the immune system, appetite, food intake, carbohydrate metabolism and protein synthesis, which, in turn, all affect athletic performance and recovery.

Slow-wave sleep or deep sleep is believed to be essential for optimal recovery in athletes as growth hormone, which is secreted during this phase, creates the optimum environment for anabolism (1). When athletes experience sleep deprivation, this reduces their slow-wave sleep, makes them feel sleepier during the day and starts to adversely affect their performance (1).

Athletes are prone to sleep deprivation and poor sleeping habits. They can also be hit hard by jet lag when travelling. Their caffeine intake and stress levels are often high, especially during periods of increased training load or when a competition is coming up due to overthinking and worrying (1). Studies have shown that sleep deprivation in athletes can lead to a significant decrease in isokinetic performance, vertical jump performance, sprint time, maximal strength, increased perceptual effort and slower and less accurate cognitive performance (1). A lack of sleep can also result in metabolic and endocrine changes, such as decreased insulin sensitivity, increased cortisol concentrations, increased ghrelin levels and decreased leptin levels, which lead to greater hunger and poor appetite control (1, 2). Sleep deprivation can also lead to immuno-depression and a higher risk of illness and infection (1).

So what role does nutrition play in relation to sleep? This is highly individual of course, but there is some evidence to suggest that high-carbohydrate diets, particularly high-GI foods, decrease the time it takes to fall asleep; high-protein diets may improve sleep quality; while high-fat diets and total caloric restriction may negatively affect sleep (1, 3).

I agree that some good-quality carbohydrates such as bananas, oats, rice and potatoes could be helpful as they increase levels of tryptophan, a precursor of the sleep-inducing compounds serotonin and melatonin, in the brain. However, not all carbohydrates are the same. Poor-quality carbohydrates such as white bread, sugary biscuits, commercial chocolate and sweets will only make matters worse in the long run as they cause major blood sugar spikes that can lead to an energy crash and trigger cravings for more. Plus, some preliminary evidence shows that simple sugars could adversely affect the duration of slow-wave sleep, likely due to a diet-induced reduction in growth hormone secretion (3).

Fatty fish is a great source of omega-3s and vitamin D, both important regulators of serotonin production (3). Increasing the intake of foods high in tryptophan such as pumpkin seeds, nuts and turkey also seems to help, while calcium-rich foods help the brain to produce melatonin (1, 3). Your mother was right to give you a glass of milk before bedtime!

A couple of studies in insomniacs have shown that drinking tart cherry juice twice a day for two weeks can extend sleep and enhance sleep quality. This is thought to be due to an increase in exogenous melatonin and high-antioxidant levels that reduce inflammation (4, 5). Eating a kiwifruit or two before bedtime may also be beneficial because of the high antioxidant and serotonin levels. Kiwifruit has also been shown to improve the time it takes to fall asleep, as well as sleep duration and quality in adults with sleep problems (6).

I also advise athletes who have difficulty relaxing and sleeping to increase their intake of magnesium-rich foods (e.g. spinach, seeds, nuts, milk, dark chocolate, avocados and bananas) and to bath in Epsom salts as the magnesium absorbed through the skin is considered to be a natural muscle relaxant. The calming effect of a cup of camomile tea is also worth a try and, finally, we should never underestimate the power of napping.

References

  • - Halson S (2014). Sleep in Elite Athletes and Nutritional Interventions to Enhance Sleep. Sports Med. 44 (Suppl 1):13-23.
  • - Beccuti, et al (2011). Sleep and obesity. Curr Opin Clin Nutr Metab Care. 14(4):402-412.
  • - St-Onge MP, et al (2016). Effects of Diet on Sleep Quality. Adv Nutr. 7(5):938-949.
  • - Liu A, et al (2014). Tart cherry juice increases sleep time in older adults with insomnia. FASEB J. 28(1): Suppl 830.9.
  • - Losso JN, et al (2017). Pilot Study of the Tart Cherry Juice for the Treatment of Insomnia and Investigation of Mechanisms. Am J Ther. [Epub ahead of print].
  • - Linn HH, et al (2011). Effect of kiwifruit consumption on sleep quality in adults with sleep problems. Asia Pac J Clin Nutr. 20(2):169-74.