Getting ready for sleep with a hot cup of cocoa or chocolate is something that many people have been doing for generations, but did you know that there really is science behind it?
One of the things that can stop you from falling or staying asleep is worry or anxiety about your day, the next day, or other things. A recent study found that cocoa helps stressed-out mice sleep better,  and another study found evidence that drinking cocoa mitigates the effects of anxiety on people.  Drinking a cup of water or milk containing some teaspoons of 100% pure cocoa or chocolate might help you cope better with stress or anxiety and help you sleep better.
This may be because cocoa or chocolate ameliorates the body’s physical signs of stress and that, in turn, feeds back to the brain by calming someone and helping them sleep. A systematic review of 42 randomised-controlled trials found that, after drinking cocoa, people had improved flow-mediated dilatation, lower diastolic blood pressure, and lower arterial pressure . That supports the wider literature showing that consuming cocoa helps the cardiovascular system and, through biofeedback, a cardiovascular system in a good state might help someone feel more relaxed and sleepy.
Research shows that psychological distress has a variety of physiological outcomes or correlates, including disturbed sleep . The psychology and physiology of stress are interlinked in many ways, which means that being physically calm can help you feel psychologically calm, and vice versa. If you are feeling psychologically worried, anxious, or stressed, cocoa or chocolate can help your body physically cope better with that state of psychological distress. By reducing your physiological distress, cocoa can help you fall asleep more easily (and more deeply) through the biofeedback process in which the body communicates its physical state of calm to the brain.
Cocoa reduces certain types of physiological distress that are related to sleep, such as blood pressure. A meta-analysis of five randomised-controlled trials found that coca significantly reduced diastolic and systolic blood pressure . People who are suffering from insomnia tend to have a higher nighttime blood pressure , so cocoa may be helpful to people who have a history of disturbed sleep. Stressful, anxious, or worrying thoughts at bedtime might also raise nighttime blood pressure and make it more difficult to fall or stay asleep. This is why drinking cocoa can help.
For optimal benefits, use pure cocoa powder (100% cocoa with no additives) so that your nighttime drink has a high cocoa content. Avoid powders that contain added sugars, chemicals, or trans fats because they might be counter-productive to health. Eating a bar of chocolate might not have the same effect as drinking water or milk containing cocoa in its pure form because chocolate might have a less pure form of cocoa, have a relatively lower dosage of cocoa per portion, and have other ingredients that affect the absorbability or benefits of the cocoa.
Research shows that products with a lower proportion of cocoa have lower levels of flavanols, epicatechin, catechin, quercetin, and theobromine, and the mental/physiological benefits of such products are lower . A drink containing two to three teaspoons of pure (100%) cocoa powder in a mug of hot water or milk is better for you than chocolate powders or drinks with added sugars, fats, or other ingredients. Such added ingredients should be avoided because of the potential negative health effects (e.g., diabetes).
If you are stressed out, anxious, or need a good night’s sleep, try a cup of cocoa.
 Oishi, K., Okauchi, H., Yamamoto, S., & Higo-Yamamoto, S. (2020). Dietary natural cocoa ameliorates disrupted circadian rhythms in locomotor activity and sleep-wake cycles in mice with chronic sleep disorders caused by psychophysiological stress. Nutrition, 110751. https://doi.org/10.1016/j.nut.2020.110751
 Boolani, A., Lindheimer, J.B., Loy, B.D. et al. (2017) Acute effects of brewed cocoa consumption on attention, motivation to perform cognitive work and feelings of anxiety, energy and fatigue: a randomized, placebo-controlled crossover experiment. BMC Nutrition 3, 8 (2017). https://doi.org/10.1186/s40795-016-0117-z
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