Most athletes track their training load, their protein intake, and their sleep duration. Almost none track pre-sleep nutritional choices — despite controlled trial evidence that specific compounds taken in the 30–90 minutes before bed produce measurable improvements in sleep architecture, next-morning readiness, and recovery markers.
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Glycine: The Amino Acid That Lowers Core Temperature
Glycine (3g taken 30–60 minutes before sleep) is the most consistently evidence-backed sleep compound with a clearly understood mechanism:
Glycine binds to glycine receptors in the hypothalamus and promotes cutaneous vasodilation — increased blood flow to the hands, feet, and skin surface, accelerating heat dissipation from the body core. The resulting drop in core temperature (approximately 0.3–0.5°C) is the direct physiological signal for sleep initiation — the same mechanism by which a cool room temperature improves sleep onset.
A 2012 RCT by Bannai et al. (*Frontiers in Neurology*) found that 3g glycine before sleep:
- Reduced sleep onset latency
- Increased time in slow-wave sleep (SWS/N3)
- Reduced daytime sleepiness and fatigue the following morning
- Improved next-day cognitive performance (memory recall, reaction time)
For athletes: glycine is also a structural component of collagen — supplementation simultaneously supports collagen synthesis in tendons and connective tissue, making it a dual-purpose recovery intervention.
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L-Theanine: Alpha Wave Induction and Anxiety Reduction
L-theanine — the primary amino acid in green tea — modulates GABAergic and glutamatergic neurotransmission in a way that promotes relaxed wakefulness before sleep onset and reduces anxiety-driven sleep fragmentation.
At 200mg (the studied dose in most RCTs), L-theanine:
- Increases alpha brain wave activity (8–12 Hz) — the neural signature of calm, awake relaxation, distinct from the slower theta and delta waves of sleep itself
- Reduces cortisol response to perceived stress (relevant for athletes with high training stress or pre-competition anxiety)
- Attenuates glutamate-mediated excitatory signalling, reducing the "racing mind" that delays sleep onset under stress conditions
L-theanine synergises with magnesium (which also supports GABAergic inhibitory tone) — a combination frequently used in athlete pre-sleep stacks.
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Tart Cherry Concentrate: Melatonin and Anti-Inflammatory Dual Action
Tart cherry concentrate (Montmorency variety, 30ml twice daily — once in the morning, once before bed) is the most evidence-backed whole-food sleep intervention for athletes, with a dual mechanism:
Melatonin provision: Tart cherries contain measurable melatonin — a 2012 paper by Howatson et al. (*European Journal of Nutrition*) found that twice-daily Montmorency cherry concentrate increased urinary melatonin metabolites and improved total sleep time and sleep efficiency compared to placebo in a crossover trial.
Anti-inflammatory load reduction: Tart cherries are rich in anthocyanins and quercetin, which inhibit COX-1/COX-2 pathways and reduce systemic inflammatory burden. Lower baseline inflammation is associated with better sleep quality — the mechanism by which athletes with high DOMS or chronic training-induced inflammation experience disrupted sleep.
Combined: the melatonin component addresses circadian timing of sleep onset; the anti-inflammatory component addresses the inflammatory noise that disrupts sleep continuity in high-load training blocks. A 2010 Howatson study specifically examined DOMS and recovery following intensive exercise — tart cherry group showed significantly faster recovery in strength, reduced CK elevation, and reported less pain.
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Building a Pre-Sleep Recovery Stack
A practical evidence-based pre-sleep protocol (30–60 minutes before sleep):
| Compound | Dose | Mechanism | Evidence strength |
|---|---|---|---|
| Glycine | 3g | Core temperature reduction, SWS increase | Strong (multiple RCTs) |
| L-theanine | 200mg | Alpha wave induction, anxiety reduction | Moderate–strong |
| Tart cherry concentrate | 30ml | Melatonin + anti-inflammatory | Moderate (sport-specific) |
| Magnesium glycinate | 200–400mg | GABAergic, SWS quality | Moderate |
For athletes tracking magnesium intake alongside a broader pre-sleep micronutrient protocol — the magnesium intake estimator at winsport.uk/tools/health/magnesium-calculator calculates daily magnesium requirement based on bodyweight and activity level, identifies dietary shortfall, and flags whether supplementation is warranted. Glycine, L-theanine, and tart cherry can be layered onto an adequate magnesium foundation — but magnesium deficiency, which is common in high-volume athletes, should be addressed first as it underpins the same GABAergic sleep pathways that L-theanine modulates.
Do you currently use any evidence-based pre-sleep nutritional strategies with your athletes — or is sleep nutrition an area that falls outside the scope of your coaching conversations?