This is an article about better sleep, restorative sleep, and it has nothing to do with stuff any moron can figure out, like making sure your nightlight isn’t a 400-watt strobe light, or you don’t try to use Metallica’s greatest hits as a lullaby.
Instead, it’s about how you can use food, or the lack of it, to obtain the overall type of sleep you want or need, including the quality of that sleep.
Now, if you’re a careful reader, your pre-frontal cortex might have latched onto the phrase “type of sleep” in the preceding paragraph. It might have confused you. Hell, it should have confused you because sleep is sleep, right?
It appears not. It’s actually in your power to determine whether your sleep is geared more towards restoring and healing the body (more N3, or “slow wave sleep,” as might benefit an athlete) or whether it’s geared more towards allowing the brain to reorganize (more REM sleep).
You can do this by varying the quantity, quality, and timing of the carbohydrates you ingest either during the day or in a pre-bedtime window. Carb manipulation might also allow you to influence how long it takes for you to fall asleep, how many times you wake up during the night, and how long you sleep.
The findings are based on a recently published meta-analysis that consisted of 27 separate scientific trials and resulted in 16 different data sets. The study, which appeared in the journal Nutrients, had the following objectives:
- Examine the effect of quantity of carbohydrate consumption on sleep quantity (how long you sleep), continuity (how long you sleep without waking up), and architecture (basic structural organization that takes the stages of sleep into consideration).
- Address potential effects of the quality of carbohydrates (e.g., glycemic index or glycemic load) on sleep quantity, continuity, and architecture.
- Investigate the effect of the timing of the carbohydrate consumption on sleep quantity, continuity, and architecture.
What they found was fascinating.
Lead scientist Angelos Vlahoyiannis and his colleagues were looking for how alterations in both quantity and quality of carbohydrates could affect sleep efficiency. The subjects in the pooled results were categorized as either falling into a low-carb group or a high-carb group.
To be specific, those subjects that had pre-bed meals of 0 to 47 grams of carbohydrate or who were ingesting between 2 and 100 daily grams of carbs were classified as low-carb subjects.
Conversely, those that had pre-bed meals consisting of 130 to 196 grams of carbohydrate or whose daily carb intake ranged from 240 grams to 600 grams were classified as high-carb subjects.
The types of carbs eaten by both groups were also classified as “high quality” or “low quality,” which simply referred to the glycemic index (GI) or glycemic load (GL) of the carbs they ingested. Foods that have a GI of less than 10 (low) or between 11 and 19 (medium GI) were considered high-quality carbs, while those that registered a GI of greater than 20 were considered low-quality carbs.
The purpose of all the compiled papers was to determine if the amount of carbs and the quality of the carbs eaten before bed or in the daylight hours before bed might influence the following specific sleep factors:
- TST – Total Sleep Time
- SE – Sleep Efficiency
- SOL – Sleep Onset Efficiency (how long it takes to fall asleep)
- WASO – Wake After Sleep Onset (how often you wake up after falling asleep and how long it takes to fall back asleep)
- ROL – REM Onset Latency (the interval between sleep onset and the onset of the first REM sleep period)
- Stage 1 (N1) Sleep – Duration of this phase of sleep
- Stage 2 (N2) Sleep – Duration of this phase of sleep
- Stage 3 (N3) – Duration of Slow Wave Sleep (SWS)
- REM Sleep – Duration of REM sleep
As a testament to the quality of the meta-study, each included trial used a comparator group that received a different quantity, quality, or timing of carb consumption. In some cases, though, the members of comparator groups received an amount of an alternate nutritive source (fat) that was calculated to have an equal amount of calories as the carb group(s).
The overall finding was that carb intake can significantly affect both sleep architecture, sleep initiation, and sleep continuation. Specifically:
- A lower intake of carbohydrate significantly lengthens N3 stage sleep duration and proportion compared to high CHO consumption. (This is hugely significant to athletes, as I’ll explain in the next section.)
- Increased carbohydrate consumption prolongs REM sleep compared to low carbohydrate intake.
- SOL (how long it takes you to fall asleep) was affected by both carb quantity and quality, with high carb and high GI carbs causing subjects to fall asleep faster.
- Varying the carb quality had significant effects on sleep continuation in general. (High glycemic index carbs reduced SOL while increasing total sleep time and overall sleep efficiency.)
I’ve Heard of REM Sleep, But What the Hell is N3 Sleep?
N3 sleep is sometimes referred to as “Delta Sleep” or slow wave sleep. It’s of particular note because N3 sleep is a regenerative period where the body heals and repairs itself. The first stage of N3 sleep generally lasts around 45 to 90 minutes while subsequent N3 sleep cycles are successively shorter and shorter (sleep cycles repeat themselves throughout the night).
Is this making your Spidey sense tingle? It ought to because N3 sleep is the athlete’s sleep zone. It’s when the body heals, grows, and comes back stronger. This period corresponds with roughly 70% of nightly growth hormone (GH) pulses, and the longer the sleep phase is, the greater the release of GH.
Cut into the duration of this period often enough, and athletic failure is a certainty. Eat low-carb meals before bed, though, and you lengthen it. How much? Vlahoyiannis calculated it to be a 16% increase in the time spent in this important restorative sleep phase.
(Incidentally, the appearance and duration of N3 sleep diminishes with age and may even be totally absent in elderly people, even if all other sleep parameters seem to be normal. Perhaps carb manipulation might resurrect this important phase and slow down the aging process?)
Depending on your perspective, there’s a potential downside to this N3-intensifying phenomenon of low carbs before bed, though: It reduces REM sleep. Now, if you know anything about sleep at all, you’ve probably heard of REM sleep. It’s the period of sleep where the brain reorganizes itself. It’s essential to learning and forming memories.
However, it may not be all that it’s trumped up to be. Deprive young people of REM sleep and you don’t notice any detriment to their behavior or psychomotor function. Deprive them of Slow Wave Sleep (N3), though, and you see a marked reduction in behavioral function. Do it several nights in a row, though, and health in general deteriorates.
The Mechanisms Behind the Effects of Carbs on Sleep Quality and Quantity
The effects of low carbs on deep sleep (N3) are probably attributable to diet-dependent hormone mechanisms. Low-carb meals lead to higher post-meal levels of cholecystokinin (CCK), which increases subjective feelings of sleepiness. Along the same lines, CCK induces higher levels of peptide tyrosine tyrosine (PYY), which also decreases wakefulness and enhances non-REM sleep.
As far as increased pre-bed carb intake lengthening REM sleep, it likely has to do with the effect of insulin on tryptophan regulation. After a big meal, insulin triggers the uptake of large amino acids, thus providing less competition for tryptophan, which is then able to traipse across the blood/brain barrier unmolested.
These increased levels of tryptophan lead to the production of greater amounts of serotonin, which is the precursor of melatonin, the “sleep-regulating hormone” that has significant effects on sleep onset latency, sleep time, sleep continuity, and sleep stages.
This was consistent across the included studies as increased carbohydrate intake in a pre-bed meal ranging from 130 grams to 196 grams (about a cup and a half to two cups of muesli cereal, for example) or in a daily dietary plan where carb intake ranged from 240 grams to 600 grams prolonged REM sleep by 8.9 minutes.
Any way you biochemically parse it, it appears that, at least in a specific time frame, increases in REM sleep (through high carbs and serotonin/melatonin production) result in a reciprocal reduction in Non-REM sleep (e.g., slow wave or N3 sleep).
Vlahoyiannis and his colleagues even speculated that the reason for this is that the metabolic demands of REM sleep are higher compared to slow wave sleep (N3), thus causing REM sleep to be reduced when dietary carbohydrate is limited and vice versa.
A Recap and How to Use This Info
Higher carb intake in the pre-bed hours may help you fall asleep faster and may lead to increased duration of REM sleep. However, low-carb intake in the pre-bed hours may facilitate increased duration and proportion of deep sleep, the kind that heals and restores the athlete’s body.
Vlahoyiannis and his colleagues summarized it this way:
“Results of the present meta-analysis support the employ of CHO quantity as a reasonable non-pharmacological tool for modification of sleep architecture if needed. As appropriate, high CHO quantities could be used to potentially increase REM, while lower CHO could be useful to increase N3 sleep stage.
“Since 1980, SWS (slow wave sleep) has been suggested to be associated with widespread bodily restorative functions, while REM sleep may be more associated with synthetic processes of brain reorganization and repair.”
So the course seems clear, at least if you believe the findings of this meta study:
For hard-training athletes, use the low-carb pre-bed approach to facilitate healing and instead load up on protein. While it may shorten REM sleep a bit, it likely won’t be enough to affect any behavior, psychomotor functions, or mental abilities.
For those who may, in certain instances, prefer longer REM periods (like when you’re studying for an exam), you can get your hit of sleep-regulating hormones without eating a waistline damaging amount of carbs – just take between 3 and 5 mg. of melatonin an hour or so before you hit the sack.
- Angelos Vlahoyiannis, et al. “A Systematic Review, Meta-Analysis and Meta-Regression on the Effects of Carbohydrates on Sleep,” Nutrients, 2021, 13, 1283.
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