Poor sleep (either insufficient duration of sleep or low-quality sleep) is associated with a weakened immune system, Alzheimer’s, disrupted blood sugar levels, cardiovascular disease, psychiatric conditions, and more. It’s also frighteningly common. The majority of adults in developed nations fail to meet the recommended amount of nightly sleep, and the World Health Organization (WHO) has even declared a sleep loss epidemic throughout industrialized countries.
In a study exploring the associations between sleep duration and mortality in Japanese men and women, researchers found a U-shaped relationship between sleep and mortality, suggesting that increased mortality is associated with both short and long sleep. Seven hours per night is the sweet spot according to this study. The consensus recommendation from the American Academy of Sleep Medicine and Sleep Research Society is similar: “Adults should sleep 7 or more hours per night on a regular basis to promote optimal health… sleeping more than 9 hours per night on a regular basis may be appropriate for young adults, individuals recovering from sleep debt, and individuals with illnesses.”
One way to measure the severity of the poor-sleep crisis is to look at the market for sleeping aids: sleep apnea devices, medications, etc. According to one research report, the global market for sleeping aids in 2021 was valued at 64.08 billion US dollars. They forecast that the market will nearly double by 2030, reaching almost 120 billion US dollars. For comparison, that forecasted amount is more than the combined global market size in 2022 for the production and distribution of movies and music (110.7 billion USD).
How can we improve this situation? And is there a role for nutrition?
The importance of having a regular sleep schedule will make intuitive sense to parents or anyone who has seen what happens when children get off of a regular sleep schedule. But kids aren’t the only ones who can benefit from regularity: cognitive behavioral therapy for insomnia (CBT-I)—perhaps the most effective behavioral method for improving sleep—prescribes that patients establish regular bedtime and wake-up times, even on weekends.. In a 2018 article published in Scientific Reports, researchers emphasized the importance of sleep regularity for decreasing the risk of cardiovascular disease, obesity, hypertension, and more.
The timing of our eating also makes a difference. In a 2015 study, researchers assessed eating patterns in adults; their findings contained a lot of variability: “Most subjects ate frequently and erratically throughout wakeful hours [emphasis added],” with a bias toward eating later in the day and differences between weekdays and weekends. They then took overweight individuals with a greater-than-14-hour feeding window and instructed them to reduce to 10–11 hours/day for 16 weeks. This relatively modest change was not combined with any specific nutrition recommendations or caloric restriction, yet the subjects enjoyed weight loss, increased energy, and improved sleep.
The National Sleep Foundation recommends not eating within 2–3 hours of bedtime, and you might want to extend that even more when it comes to foods heavy in proteins that promote the synthesis of dopamine, “a wake-promoting neurotransmitter.”
You might also want to avoid foods and beverages that hinder high-quality sleep, including caffeinated substances, chocolate, and sugar-sweetened beverages (SSBs).
And this advice applies not only immediately before bedtime. It takes several hours for caffeine to leave your system, as researchers found in a study published in 2013. Whether taken zero, three, or six hours before bedtime, caffeine ingestion had “significant effects on sleep disturbance relative to placebo.” A word of caution about this study, however: The caffeine dose was quite large (400 mg), equivalent to more than two grande-size Starbucks iced caffé mochas. That isn’t to say smaller doses of caffeine won’t also disturb your sleep, only that the degree of disturbance might be less than what the researchers observed.
So, does that mean you should avoid all caffeine-containing beverages? Not necessarily. That’s an assessment you’ll have to make based on your current level of sleep quality and the balance of health benefits. Green tea, for instance, provides many health benefits, certainly more than a Starbucks caffé mocha. And you’d have to drink more than 14 eight-ounce cups of brewed green tea to reach the 400 mg of caffeine in the study above!
It’s also worth noting that what we ingest can affect our sleep in ways we might not immediately notice. In a study of Iranian adults, researchers found that sleep quality but not duration was associated with intake of SSBs, “especially in younger and non-obese individuals.” In other words, you might not have difficulty falling asleep—and you might not even feel any different after only one or two nights—but eventually, you’ll likely feel the cumulative effects of being less well-rested.
Besides avoiding the obvious foods and beverages, what does the research say about broader dietary habits and sleep quality? According to a recent study, “whole diets rich in fruits, vegetables, legumes… have been shown to predict favorable sleep outcomes.” This idea is supported by a systematic review that included 29 studies in which researchers found the consumption of healthy foods associated with higher-quality sleep. While there wasn’t a consistent definition of what constitutes a “healthy diet” in the reviewed studies, certain patterns emerged, “including high intake of plant-derived foods… whole-grains and legumes,” often as part of a Mediterranean-style diet. Conversely, the consumption of processed foods was associated with lower sleep quality.
The contrast between natural plant-based foods and processed junk food is consistent with the researchers’ remarks about carbohydrates: “rather than mere quantity, the reviewed studies pointed that the type of carbohydrates may be a more important target…”
So, context matters—what’s new?
Non-nutritional factors affecting sleep include exercise, sleep hygiene, and stress. And these are interrelated. For instance, there is a cyclic relationship between sleep and exercise: the better you sleep, the higher your energy and fitness levels will become, and the more you exercise, the better your sleep will become. Stress is similar: sleep-deprived individuals are more likely to struggle with stressful situations, and stress contributes to poor sleep.
Here are some general tips for improving your sleep hygiene from the 2017 bestseller Why We Sleep:
So you’ve eliminated the things that disrupt sleep, you’re eating a healthy plant-based diet, and you’ve adopted better habits by following the tips above. What if you still can’t sleep?
Several specific foods and drinks have been associated with improved sleep (in the case of honey, the improvement may owe more to the alleviation of upper respiratory tract infection symptoms rather than the direct effect of honey on sleep):
However, I would warn against seeking a quick fix from any of these individual foods or beverages (or the nutrients they contain) in isolation. If you want to try integrating them into your sleep routine and find that they help you sleep better—fantastic! But there are no shortcuts that will overcome unhealthy sleep behaviors, and the total effect of these foods and drinks on our health is, as usual, going to be most profound as part of a broad, whole food, plant-based diet.
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