A RESEARCH REVIEW ON THE TOPIC The relationship between sleep and nutrition and the functional-food interventions that may influence athletic performance has been explored recently by researchers, discussed in an review article, “Sleep and Nutrition Interactions: Implications for Athletes” authored by scientists in Ireland and the United Kingdom in the journal Nutrients.
The in-depth piece examines the basics of sleep, athletics and sleep, nutritional support of sleep in athletes, timing of nutrition for athletes, and specific nutrients and food substances which may have potential as interventions.
We all rely on sleep to maintain healthy cognitive functioning, regardless of athletic status. Among other problems, insufficient or poor-quality sleep can lead to poor performance of everyday tasks, inattention, and forgetfulness at school and on the job, explains the Sleep Foundation’s website. On the other hand, adding exercise to a schedule that does not routinely include it can improve sleep.
This scientific publication’s authors instruct us that the well-known restorative effect of sleep is especially important to athletes who must meet challenging physical and psychological demands imposed by training and competition, Improving sleep quantity and quality they indicate, can help with recovery and injury prevention, as well as “learning, memory and synaptic plasticity” which impact training adaptations and performance.
Athletes involved in regular training activities are asking their bodies and nervous systems to learn to coordinate functions at more elevated levels. They are expecting muscles, bone, brain, senses, nerves, metabolism, heart, and lungs to respond to coaching such that amazing skills can be developed. And that later, in competition, those skills can be purposefully called up and executed on demand. As sport spectators viewing feats of incredible athleticism, we witness what can be accomplished when “learning, memory, and synaptic plasticity” are enabled through training.
By the way, plasticity is defined as “The ability to change and adapt, especially the ability of the central nervous system to acquire alternative pathways for sensory perception or motor skills.” Just like plastic as a material can be molded, twisted, bent, and folded in its soft stage, it eventually will harden into a desired fixed form.
Our nervous systems, which direct the actions of other body tissues through signaling, can also be manipulated or trained (like plastic in its soft stage) to instruct those other tissues to accomplish new moves, such that motor skills eventually become hard-wired and nearly automatic. My father, a college football player himself and later a coach of multiple sports, used to talk about a player’s “coachability”. What he was appreciating might have been, in part, the plasticity of that player’s nervous system!
Because competitive athletes must comply with anti-doping regulations, nutritional adjustments that include supplements should be made carefully, with knowledge of potential effects on medical test results, the authors explain. Efforts to boost performance must fall within legal guidelines. Thus, scientific investigation into sleep and nutrition can be of help to athletes hoping to enhance performance by improving sleep.
The review’s in-depth discussion doesn’t easily allow a bullet-point summary. As an Earned Runs blogger trying to bring helpful information to readers, I’ve learned the details of such research publications are often worth closer examination of the full piece, even if much of what is written is “science-speak”. My understanding of the nutrition interventions covered in the report, considered by the authors to have potential to “positively impact sleep”, is given below*.
The conclusion of the review was that functional-food interventions for athletes and others “warrant further investigation”.
Few of us are professionals or high-level amateurs but as recreational fitness enthusiasts we also hope to benefit from hours of training, as well as avoid injury and illness. Mostly we wish to enjoy the time spent while physically active. Enhancing sleep experiences may be the ticket to our realizing healthier sport experiences, and nutrition may be one pathway to improved sleep.
Those who are generally interested in the science of sleep and nutrition will wish to read the full article, available as a free pdf download. It’s a terrific foundation on which to build.
My final overall impression is that a high-glycemic index carbohydrate-rich meal, ideally consumed about 4 hours before bedtime taken with milk has a chance of helping improve sleep quality and quantity.
My mother's idea of a great after dinner night snack when I was a little girl, graham crackers broken up in a bowl with milk poured over, seems like perfect. The graham crackers have a high glycemic index, are fortified with B vitamins, and contain a modest amount of magnesium. Milk contributes melatonin and tryptophan, and adds magnesium. Boost this treat with antioxidant-rich blue or red berries, maybe adding a side serving of tart cherries, and nearly all the bases are covered when it comes to potential sleep enhancing substances.
RUN & MOVE HAPPY!
*Potential Nutrition Intervention:
-Carbohydrate: consumption of carbohydrates has been demonstrated to increase the blood’s tryptophan concentration (which influences brain levels of the sleep-wake cycle neurotransmitter serotonin) through the action of insulin. Glycemic Index (GI) “has been shown to affect sleep latency”, which is the “length of time of the transition from wake to sleep.” A high glycemic index carbohydrate meal taken 4 hours before bed seems to be better at reducing sleep latency than a meal eaten only 1 hour before bedtime. On the other hand, low glycemic index meals have been associated with insomnia, which is considered “difficulty maintaining sleep”. Compared to a low GI meal or no meal at all before bed, a high GI meal taken 45 minutes before bedtime decreased several measures of insomnia.
-Melatonin: the protein melatonin is a hormone secreted endogenously (in the body) in response to darkness by a small brain gland, the pineal, and other tissues. It is considered to have sleep-facilitating effects. The review indicates it does so by influencing core temperature. Thus, it is thought that exogenously ingested (supplemental) melatonin might also improve sleep.
Sleep improvements induced by supplemental melatonin may depend on timing (earlier in evening is better compared to later) and dose (smaller is better than larger). The review indicates that compared to placebo, a 0.3mg dose, similar to the amount released by the body naturally, was equally as effective as a larger 1.0 mg dose at decreasing time to fall asleep (sleep onset latency) in 6 healthy males when given at 6pm or 8pm. But when given at 9pm the effect was reversed; compared to placebo (8 minutes to fall sleep), the 0.3mg dose increased the time to fall asleep to 25 minutes, and the 1mg dose increased it to 12 minutes.
Melatonin naturally occurs in cow’s milk, which is viewed in western countries as a sleep-promoting food. Milk’s positive sleep effects are thought to be due to both its melatonin and amino acid (tryptophan) content, discussed a bit later. Higher concentrations of melatonin (and tryptophan) are found when dairy cows are milked at night (night-time milk). Seems to make sense.
[Earned Runs note: A bit of online searching revealed that most cows in the USA are milked 2-4 times a day, spaced evenly throughout the day (12 hours apart at about 5-6am and 5-6pm, or 6-8 hours apart if more times each day). It seems likely that commercial milk would contain a mix of milk from each time rather than being separated by milking time, except when marketing information indicates this difference. A dairy in Ireland markets its “Lullaby Milk” as sleep-promoting because of the timing of milking!]
-Tryptophan-rich protein: the amino acid tryptophan (abbreviated Trp) is a precursor to the neurotransmitter serotonin, which effects the sleep-wake cycle, as well as melatonin. Ingested serotonin cannot cross the blood brain barrier (BBB), so it must be synthesized in the brain itself. Tryptophan in the diet is able to cross the BBB and there contribute to increased serotonin synthesis.
Trp transport across the BBB is tricky; it must successfully compete with other amino acids also crossing this ‘barrier’. To do so, the blood level of Trp must be higher compared with that of the other amino acids (at a higher ratio). Scientists previously thought than any protein food high in Trp would also be high in the other amino acids and the blood ratio would not likely be changed enough by intake of such foods to affect serotonin levels.
However, this theory was blown apart when a human research study showed that a meal containing the milk protein alpha-lactalbumin could increase the ratio of Trp to other amino acids.
Of all protein food sources reported to be high in natural tryptophan, including milk/cheese, poultry/eggs, beans, peanuts, pumpkin seeds, and green leafy vegetables, the milk protein alpha-lactalbumin is known to possess the highest levels.
Ultimately it was shown in rats that compared with other dietary proteins, including casein, an a-lactalbumin meal could increase 1) the Trp ratio in blood 2) the amount of Trp in the brain itself, and 3) the rate of brain serotonin synthesis. A later small human study also showed that a bump in Trp ratio could be achieved with a lactalbumin meal and not with other types of protein or starch.
If you immediately searched for information about a-lactablumin, you'll find a company is already marketing a product for healthy living.
-Antioxidants: athletes and the general public can benefit from antioxidants in food, the review indicates, which are any substance that counteracts the tissue damaging effects of oxidative molecules. Athletes are interested in them because exercise produces free-radicals (one type of oxidant) in muscle. Vitamins C, E, and A are specifically discussed. According to the review caution has been indicated with regard to high levels of antioxidant supplementation, as there may be interference with exercise training adaptations. Each substance should be considered separately, and more research is needed. [Earned Runs note: whole foods containing such antioxidants are globally recommended. It is supplementation that is questionably beneficial, and which requires caution].
--Tart-cherries: contain high concentrations of melatonin and compounds with both anti-inflammatory and antioxidant properties leading to the reduction of delayed onset muscle soreness (DOMS) and the post-exercise inflammatory response, which can interfere with sleep quantity or quality. Might be especially helpful at times high-volume training, (pre-season) multiple closely spaced performances (double training sessions or competitions).
--Kiwi fruit: may aid sleep because of serotonin or folate content or due to properties of contained anthocyanidins, carotenoids, beta-carotein, lutein, potassium, copper and fiber.
-B Vitamins and Magnesium: vitamins B3 (niacin), B6 (pyridoxine), B9, (folate), B12 (cobalamin) each play roles in the sleep-wake cycle, as does the mineral, magnesium, by effecting levels or functioning of beneficial or inhibitory neurotransmitters or their precursors in the brain. It is likely that supplemental intake will only improve sleep in instances of deficiency or insufficiency.
BRIDGE TO PHYSICAL SELF
Running, walking, and fitness activities enable us to experience our physical selves in a world mostly accessed through use of fingers on a mobile device.
EARNED RUNS is edited and authored by me, runner and founder. I began participating in road races before 5Ks were common. I've been a dietitian, practiced and taught clinical pathology, and been involved with research that utilized pathology. I am fascinated with understanding the origins of disease as well as health.
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