Evening Glycine: A Food-First Protocol to Quiet Racing Thoughts, Lower Nighttime Cortisol, and Deepen Sleep

Racing thoughts at night are more than “just stress”—they’re a brain-and-body arousal state that can reinforce insomnia, anxiety symptoms, and next-day cognitive fog. One food-first tool that’s increasingly studied for sleep depth and nighttime calm is glycine, a simple amino acid that also functions as an inhibitory neurotransmitter in the central nervous system (CNS) (Owen et al., 2016; Yamadera et al., 2007). Below is an evidence-based, practical evening protocol focused on dietary glycine to help quiet mental “noise,” support healthier sleep architecture, and improve next-day alertness.

What glycine does in the brain (and why it can feel calming)

Glycine plays two key roles relevant to mental calm and sleep quality. First, it acts as an inhibitory neurotransmitter in parts of the spinal cord and brainstem, which can support downshifting from physiological “fight-or-flight” into a more parasympathetic-ready state (Owen et al., 2016). Second, glycine also acts as a co-agonist at NMDA receptors, meaning it can modulate excitatory signaling in a way that depends on context and neural activity (Owen et al., 2016). This dual role helps explain why, anecdotally, some people experience glycine as “quieting” rather than sedating.

Sleep is tightly linked to brain thermoregulation. Controlled human studies suggest glycine may support sleep partly by promoting peripheral vasodilation (heat loss through the skin), which can lower core body temperature—an internal cue associated with sleep initiation and deeper sleep (Yamadera et al., 2007; Inagawa et al., 2006). When the body can shed heat effectively, many people find it easier to transition from mental overactivity into sleep.

Evening glycine for sleep: what human research shows

In randomized, placebo-controlled human trials, taking 3 grams of glycine before bedtime has been associated with improvements in subjective sleep quality and next-day fatigue in people with sleep complaints (Yamadera et al., 2007). Additional human work has reported improvements in measures related to sleep continuity and next-day performance (Inagawa et al., 2006). While the sleep literature is not as large as it is for melatonin or CBT-I, the existing controlled trials consistently use the ~3 g pre-bed dose and point toward better perceived sleep depth and next-day alertness (Yamadera et al., 2007; Inagawa et al., 2006).

Importantly for cognitive wellness, sleep quality is not just about feeling rested—it’s strongly associated with attention, working memory, emotion regulation, and resilience to stress (Krause et al., 2017). Any intervention that reliably improves sleep continuity and depth can indirectly support mental health outcomes by reducing vulnerability to anxiety amplification and negative mood bias after poor sleep (Krause et al., 2017).

A food-first evening glycine protocol (with grams and timing)

Clinical trials commonly use 3 g glycine close to bedtime (Yamadera et al., 2007; Inagawa et al., 2006). Getting that exact amount purely from food can be challenging on some diets, so the most practical “food-first” approach is to emphasize glycine-rich foods at dinner and, if needed, add a small, targeted supplement dose that mirrors the research.

Step 1: Build dinner around glycine-rich proteins (60–120 minutes before bed)

Glycine is especially abundant in collagen-rich connective tissues (skin, tendons, cartilage), which is why slow-cooked meats, bone broth, and gelatin-based foods are often higher-glycine options compared with lean muscle meat alone (Meléndez-Hevia et al., 2009). This matters for brain health because amino acid availability can shape neurotransmitter precursor pools and overall protein adequacy, both of which influence sleep and mood regulation (Gómez-Pinilla, 2008).

• Food-first dinner ideas: slow-cooked beef or chicken with skin-on portions; sardines or salmon plus a collagen-containing soup; or a stew made with shank/short ribs (Meléndez-Hevia et al., 2009).
• Gentler option: bone broth or a gelatin-rich soup as a pre-bed “bridge” if heavy meals worsen reflux or sleep (Krause et al., 2017).

Step 2: If you need precision, use the clinically studied pre-bed dose

If your goal is to match the strongest human evidence, consider 3 g glycine taken 30–60 minutes before bed, which is the dose used in controlled trials reporting sleep benefits (Yamadera et al., 2007; Inagawa et al., 2006). This approach is still “food-first” in spirit when your baseline diet is glycine-forward and the supplement is a targeted tool rather than a replacement for nutrition.

• Simple routine: dinner + wind-down; then 3 g glycine in water 30–60 minutes before lights out (Yamadera et al., 2007).
• Tracking tip: log sleep onset latency, awakenings, and next-day sleepiness for 10–14 nights to assess whether it meaningfully improves your sleep pattern (Krause et al., 2017).

Step 3: Pair glycine with sleep-supportive digital habits

“Racing thoughts” often intensify with cognitive stimulation and bright evening light exposure. Blue-enriched light can delay circadian phase and suppress melatonin, increasing physiological alertness at the exact time your brain needs to downshift (Chang et al., 2015). Pairing evening glycine with a digital wind-down (screen dimming, warm color temperature, or avoiding bright screens near bedtime) targets both neurochemistry and circadian timing (Chang et al., 2015).

• Set screens to warm mode and lower brightness 1–2 hours before bed (Chang et al., 2015).
• Use a low-stimulation audio routine (breath pacing, NSDR, or a guided relaxation) to reduce cognitive load and facilitate sleep onset (Krause et al., 2017).

Racing thoughts + “night cortisol”: what’s realistic, what’s supported

The term “night cortisol” is often used online to explain insomnia, but cortisol normally follows a circadian rhythm (low at night, rising toward morning). Sleep loss and insomnia are associated with physiological hyperarousal and changes in stress-system signaling, which can include altered HPA-axis activity in some individuals (Buckley & Schatzberg, 2005; Riemann et al., 2010). In other words, stress biology and insomnia can reinforce each other—even when the original trigger was psychological (rumination) rather than hormonal.

Direct evidence that glycine specifically lowers nighttime cortisol in humans is limited, so it’s more accurate to view glycine as a tool that may support sleep initiation and depth via thermoregulation and neurotransmission (Yamadera et al., 2007; Owen et al., 2016). Better sleep itself is associated with healthier emotion regulation and reduced next-day reactivity to stress, which can indirectly improve perceived “wired-but-tired” patterns over time (Krause et al., 2017; Riemann et al., 2010).

If your racing thoughts are primarily worry-based, combining dietary strategies with evidence-based behavioral tools matters. Cognitive behavioral therapy for insomnia (CBT-I) is a first-line treatment for chronic insomnia and can also improve comorbid anxiety/depressive symptoms, supporting both sleep and mental health (Trauer et al., 2015).

• If thoughts are repetitive: do a 5-minute “worry download” earlier in the evening, then schedule a short problem-solving window the next day—this mirrors CBT-I/CBT strategies that reduce bedtime rumination (Trauer et al., 2015).
• If your body feels physically keyed up: keep the bedroom cool and use a consistent wind-down window; thermoregulatory support is one hypothesized pathway for glycine’s sleep effects (Yamadera et al., 2007).

Safety, interactions, and who should be cautious

Across human studies using bedtime glycine, the 3 g dose has generally been well tolerated (Yamadera et al., 2007; Inagawa et al., 2006). That said, individual responses vary, and sleep supplements can complicate care if you have medical conditions or are using sedating medications.

• If you take psychoactive or sedating medications: discuss glycine with your clinician; sleep changes can interact with overall treatment planning, and insomnia is commonly comorbid with mood and anxiety disorders (Krause et al., 2017).
• If you have chronic insomnia (>3 months): prioritize CBT-I as the evidence-based foundation; supplements are best used as adjuncts (Trauer et al., 2015).
• If glycine causes GI upset: try splitting the dose (e.g., 1.5 g after dinner + 1.5 g pre-bed) or take it with warm water; discontinue if symptoms persist (Yamadera et al., 2007).

Finally, remember that dietary patterns influence brain function at a systems level. Diet quality is associated with depression risk and overall mental well-being, and sleep often improves when nutrition supports stable energy and neurotransmitter synthesis (Lai et al., 2014; Gómez-Pinilla, 2008). Glycine can be one useful lever, but it works best inside a broader brain-supportive diet and sleep routine.

Conclusion

Evening glycine is a practical, research-backed option for people who feel mentally “switched on” at night and want a food-first strategy to support deeper, more restorative sleep. Human trials using 3 g pre-bed show improvements in subjective sleep quality and next-day fatigue, likely via glycine’s inhibitory neurobiology and thermoregulatory effects (Yamadera et al., 2007; Inagawa et al., 2006; Owen et al., 2016). For best mental-health payoff, pair glycine-forward dinners (collagen-rich foods) with a consistent digital wind-down and consider CBT-I if insomnia is persistent (Chang et al., 2015; Trauer et al., 2015).

References

• Buckley, T. M., & Schatzberg, A. F. (2005). On the interactions of the hypothalamic-pituitary-adrenal (HPA) axis and sleep: Normal HPA axis activity and circadian rhythm, exemplary sleep disorders. Journal of Clinical Endocrinology & Metabolism, 90(5), 3106–3114. https://doi.org/10.1210/jc.2004-1056
• Chang, A.-M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 112(4), 1232–1237. https://doi.org/10.1073/pnas.1418490112
• Gómez-Pinilla, F. (2008). Brain foods: The effects of nutrients on brain function. Nature Reviews Neuroscience, 9(7), 568–578. https://doi.org/10.1038/nrn2421
• Inagawa, K., Hiraoka, T., Kohda, T., Yamadera, W., Takahashi, M., & Ozone, M. (2006). Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep and Biological Rhythms, 4(1), 75–77. https://doi.org/10.1111/j.1479-8425.2006.00193.x
• Krause, A. J., Simon, E. B., Mander, B. A., Greer, S. M., Saletin, J. M., Goldstein-Piekarski, A. N., & Walker, M. P. (2017). The sleep-deprived human brain. Nature Reviews Neuroscience, 18(7), 404–418. https://doi.org/10.1038/nrn.2017.55
• Lai, J. S., Hiles, S., Bisquera, A., Hure, A. J., McEvoy, M., & Attia, J. (2014). A systematic review and meta-analysis of dietary patterns and depression in community-dwelling adults. The American Journal of Clinical Nutrition, 99(1), 181–197. https://doi.org/10.3945/ajcn.113.069880
• Meléndez-Hevia, E., de Paz-Lugo, P., Cornish-Bowden, A., & Cárdenas, M. L. (2009). A weak link in metabolism: The metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis. Journal of Biosciences, 34(6), 853–872. https://doi.org/10.1007/s12038-009-0100-9
• Owen, L., Sunram-Lea, S. I., & Richardson, A. J. (2016). The role of glycine in neurophysiology and mental health: A review of evidence. Neuroscience & Biobehavioral Reviews, 71, 212–223. https://doi.org/10.1016/j.neubiorev.2016.09.012
• Riemann, D., Spiegelhalder, K., Feige, B., Voderholzer, U., Berger, M., Perlis, M., & Nissen, C. (2010). The hyperarousal model of insomnia: A review of the concept and its evidence. Sleep Medicine Reviews, 14(1), 19–31. https://doi.org/10.1016/j.smrv.2009.04.002
• Trauer, J. M., Qian, M. Y., Doyle, J. S., Rajaratnam, S. M. W., & Cunnington, D. (2015). Cognitive behavioral therapy for chronic insomnia: A systematic review and meta-analysis. Annals of Internal Medicine, 163(3), 191–204. https://doi.org/10.7326/M14-2841
• Yamadera, W., Inagawa, K., Chiba, S., Bannai, M., Takahashi, M., & Nakayama, K. (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms, 5(2), 126–131. https://doi.org/10.1111/j.1479-8425.2007.00265.x

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