Poor sleep has been shown to lower athletic (1) and cognitive performance (2), to effect mood (3), change glucose metabolism (4), suppress appetite regulation (5), and immune function (6) increase blood pressure (7) and raise perception of stress (8).
Poor sleep is common in athletes, particularly footballers and can be a problem for anyone from working professionals to teenagers, particularly near to deadlines or during exams, when performance is important.
In my post Sleep and Performance, I talked about different pattens of sleep and the research linking different phases and amounts of sleep to performance. In this post the aim is to follow on from that work and look at research linking sleep to diet – how nutrition can improve both the quality and quantity of sleep.
A lot of sleep research has centred around melatonin. Melatonin is a hormone made by the pineal gland in the brain and although it has other roles, its association with the wake-sleep cycle appears to be relatively straight forward. During the day the pineal is inactive but when the sun goes down and it gets dark, the pineal begins to actively produce melatonin and release it into the blood stream. As melatonin levels rise (generally around 9pm) you begin to feel less alert or sleepy. Approximately 5000-28,000ng of melatonin is secreted into the blood stream of healthy individuals during the night, blood levels peak between 3am and 5am and stay elevated for about 12 hours. Daytime levels are barely detectable.
Low level melatonin supplementation has been shown to be effective in improving sleep in both children and adults and eating foods containing natural sources of melatonin have been found to improve both the quality of sleep and the ease with which individuals get to sleep. Recent research has concentrated on tart cherries as a particularly good source but a number of other foods contain natural sources of melatonin. The main ones are shown in the table below. Raspberries and goji berries are also often given as good sources but I’ve been unable to find reliable numbers for their melatonin content.
|Tart Cherries||1,350ng/100g (fresh) 17,535ng/100g (concentrate)|
Low serotonin levels result in sleep disruption and sleep disorders, including insomnia but because of its wide number of other roles in the body its relationship with sleep and relaxation isn’t as straight forward as it is with melatonin. Serotonin can be found in a wide variety of foods, particularly walnuts, plantain, pineapple, banana, kiwi, plum and tomato and eating these foods has been shown to boost serotonin levels in the gut. Unfortunately though serotonin does not pass through the blood-brain barrier and so eating serotonin rich foods may not help with insomnia or poor sleep latency.
Bright light and exercise during the day both increase brain serotonin levels as do mindfulness practices, meditation, yoga and choir singing.
Foods Containing L-tryptophan
L-tryptophan is an amino acid and is the precursor of melatonin and serotonin as well as being involved in the production of hydroxytryptophan (5-HTP), which is also linked to positive sleep patterns. Although tryptophan crosses the blood-brain barrier and purified tryptophan has been shown to increases brain serotonin, unfortunately research has found that foods containing tryptophan do not (11). This is because tryptophan is transported into the brain by an active transport system shared with all the large neutral amino acids and tryptophan is the least abundant in protein. This means where there is competition between amino acids for the transport system after a meal containing protein, the level of the other large neutral amino acids will prevent the increase in tryptophan.
Despite this fact, there is evidence that we crave foods rich in tryptophan when serotonin levels are low and I believe this means its worth a try. Foods that are particularly rich in tryptophan include turkey, bananas, milk, yoghurt, eggs, meat, nuts, pumpkin seeds, sesame seeds, soy, beans and fish. Studies have shown that ingesting carbohydrates boosts brain tryptophan levels and serotonin synthesis.
Turning tryptophan into melatonin requires folic acid, vitamin B6, vitamin C and zinc.
According to some research foods rich in carbohydrates make tryptophan more available to the brain, thus boosting the production of serotonin and melatonin. Eating small carbohydrate-rich snacks, such as granola, unsweetened cereal, whole-grain bread or crackers with tryptophan-containing milk before bed may help reduce insomnia, improving time to get to sleep and depth of sleep.
The carbohydrates need to be unrefined though…. research also shows that high blood sugar during the night causes your kidneys to go into overdrive to try and get rid of the excess sugar by urinating. This has been sited as one of the main reasons that professional sports people have disturbed sleep before and after competition.
There have been several small studies that suggest dietary magnesium can play a role in sleep. Magnesium definitely promotes muscle relaxation, which may help you to sleep. When your body doesn’t get enough magnesium, anxiety and sleep disturbances can occur. Magnesium deficiency can also result in uncomfortable sensations in the legs known as restless leg syndrome, which can affect your ability to sleep. Foods rich in magnesium include legumes, whole grains, leafy green vegetables, Brazil nuts, almonds, cashews, pumpkin seeds, pine nuts and black walnuts. Bran cereals, oatmeal, bananas, chocolate, seaweed and the herbs basil, tarragon, marjoram and dill.
Lactucarium is the milky fluid secreted by several species of lettuce, especially Lactuca virosa, when you pick it. Lactucarium is known as lettuce opium because of its sedative and analgesic properties. Fans of Peter Rabbit will remember that he felt incredibly sleepy after raiding the lettuces in Mr McGreggors garden. Lettuce lactucarium does have sedative properties. I suspect the amounts needed to have a big effect are pretty large but some athletes swear by a large green or caesar salad before bed.
Above I have given the facts. Unfortunately every case is different and what works for one person may not necessarily work for another. In general, eating regular meals, cutting out refined carbohydrates and sugar where ever possible, avoiding too much caffeine and adding in foods that are thought to aid sleep like those with high levels of melatonin or tryptophan will all help.
If you are a footballer or athlete that competes either at lunchtime or late in the evening, there are other things you should / could consider and I would be happy to give one-on-one advice.
If you are feel that your sleep maybe being effected by stress again there are other things you should think about, that I would be happy to share.
REFERENCES & FURTHER READING
1. Halson 2013. Sleep and the Elite Athlete. Sports Science Exchange 26(113), 1-4
2.Walker 2009. The Role of Sleep in Cognition and Emotion. The Year in Cognitive Neurosciene. Ann N.Y Avad Sci 1156, 168-197
3. Belenky G, Wesensten NJ, Thorne DR, et al. Patterns of per- formance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose–response study. J Sleep Res. 2003;12(1):1–12.
4. Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. Lancet. 1999;354(9188): 1435–9.
5. Spiegel K, Tasali E, Penev P, et al. Brief communication: sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004;141(11):846–50.
6. Krueger JM, Majde JA, Rector DM. Cytokines in immune function and sleep regulation. Handbook Clin Neurol. 2011;98: 229–40.
7. Ogawa et al 2003. Total sleep deprivation elevates blood pressure through arterial baroreflex resetting : a study with microneurographic technique. SLEEP 26(8). 986-989
8. Spiegel et al 1999. Impact of sleep debt on metabolic and endocrine function. The Lancet. 354(9188), 1435-1439
9. Howatson, Glyn, Bell, Phillip, Tallent, Jamie, Middleton, Benita, McHugh, Malachy and Ellis, Jason(2012) Effect of tart cherry juice (Prunus cerasus) on melatonin levels and enhanced sleep quality.European Journal of Nutrition, 51 (8). pp. 909-916. ISSN 1436-6207
10. Shilo et al 2002. The effects of coffee consumption on sleep and melatonin production. Sleep Medicine 3(3),271-3
11. Wurtman RJ, Hefti F, Melamed E. Precursor control of neurotransmitter synthesis. Pharmacol Rev1980;32:315-35. [PubMed]