We’ve all been told that sleep is important for our health and how getting 7 to 9 hours per night benefits our mental, physical, and emotional well-being. But an estimated 50 to 70 million Americans struggle to get sufficient sleep on a regular basis despite these recommendations.
And women may be more tired than men. A 2017 study in the Journal of Clinical Sleep Medicine found that women experience sleep disorders at higher rates than men, feel the effects of those disorders more often, and struggle with sleep-related memory and concentration as a result.
So how important is sleep really?
Sleep impacts a number of bodily functions like metabolism, blood sugar control, appetite, cravings, digestion, body temperature, hormone release, memory, mental wellness, and recovery.
It makes sense then that a lack of sleep (< 7 hours per night) is linked to various health conditions like insulin resistance, diabetes, obesity, cardiovascular disease, hypertension, depression, anxiety, bipolar disorder, seasonal affective disorder, and sleep disorders like insomnia.
And beyond what’s happening within our bodies, we can all relate to the feeling of being under- rested: Slow reaction time, poor focus and productivity, reduced tolerance for stressors, and a harder time making sound decisions after a night of short sleep make getting through the day feel like an impossible feat.
What do we define as good sleep?
While sleep durations differ throughout the lifespan, the average healthy adult should aim for 7 to 9 hours of sleep per night. But good sleep goes beyond quantity. High-quality sleep is defined as being continuous and lends to falling asleep quite easily, not fully awakening during the night, not waking up too early, and feeling refreshed in the morning.
What’s happening behind the scenes in our bodies to impact our sleep?
Let’s chat about circadian rhythms
The body maintains an internal “master clock” that coordinates several cycles—known as circadian rhythms—that repeat on a 24-hour basis. Both humans and animals have a number of mental and physical systems that are regulated by their own circadian rhythms. For example, our digestive systems follow a unique rhythm that helps our bodies regulate blood sugar differently when we’re awake versus when we’re asleep.
Our master clock is directly influenced by changes in our environment, especially light—which explains why our circadian rhythms are tied to cycles of day and night.
A quick overview of sleep hormones
Two major hormones regulate our sleep-wake cycles: cortisol and melatonin.
Cortisol is made by our adrenal glands. It impacts many systems in the body like our metabolism and immunity, but is most widely known for its role in the body’s stress response.
Cortisol levels increase two to three hours after we fall asleep and continue to rise until our waking hours, with our cortisol levels peaking around 9 a.m. Short-term releases of cortisol are important—cortisol is what gets us up and out of bed in the morning and helps us respond to stressful situations. But when cortisol levels remain high for too long, or when cortisol is released at the wrong time, negative health effects can occur, including disrupted sleep and weight gain.
Cortisol levels decline throughout the day until they reach their lowest concentration at midnight. As cortisol levels drop, levels of melatonin increase.
Melatonin is a hormone that the brain and bacteria in the gut produce in response to darkness. Melatonin has a variety of functions but is most widely known for its role in increasing feelings of tiredness. Our melatonin levels rise a few hours before our habitual bedtime. Darkness signals the release of melatonin while light inhibits it.
How modern living affects our sleep-wake cycle
When we listen to and honor our body’s natural sleep-wake cycle by going to bed when we’re tired and waking up when we’re rested, we get consistent and restorative sleep and optimize our body’s ability to function properly.
But, as humans, we’re able to override these cues. We often trade in Z’s for late-night work, Netflix, social media scrolling, or a few extra moments for ourselves after a busy day, sometimes with a glass of vino (which, despite making us feel drowsy, may actually interfere with our sleep).
Here’s what happens after just one night of poor sleep:
- Our hunger increases, and we eat more: Two major hormones regulate our appetite: leptin and ghrelin. Leptin signals feelings of fullness after eating and ghrelin signals feelings of hunger after periods of fasting. Inadequate sleep can lead to decreased secretions of leptin and increased secretions of ghrelin, leading us to feel hungrier and less satisfied the day following a night of poor sleep. Most often we respond to these changes by increasing our intake of food. The good news? Leptin levels are thought to be restored to their baseline levels after a good night of recovery sleep.
- We experience cravings and gravitate towards more high-carb, high-fat foods: Multiple studies show that inadequate sleep (~5.5 hours per night) may lead to increased consumption of daily calories, particularly those from high-carbohydrate snacks and high-fat foods the day following poor sleep, especially at night. Various studies show that poor sleep (~5 hours) and disruptions in circadian rhythm may increase our hedonic drive for food—in other words, our desire to eat foods for pleasure and reward rather than to satisfy biological hunger. These effects may be magnified for night shift workers who experience chronic disruptions in their sleep-wake cycle. There’s a biological explanation as to why most of us opt for pastries, pizza, and pasta instead of salads and smoothies after a night of poor sleep, even if we’ve nailed the habit of balanced eating.
- Our blood sugar gets out of whack despite healthy choices: Research shows that sleep deprivation (< 7 hours) increases insulin resistance and decreases glucose tolerance the following day. What exactly does this mean? After just one night of poor sleep, insulin—a hormone that regulates blood sugar—doesn’t do its job effectively. And, as a result, not only do blood sugar levels spike rapidly, they also remain elevated long after eating, even if our meals include healthy foods like protein, fiber, healthy fats, and complex carbohydrates. Chronically elevated levels of blood sugar are a risk factor for type II diabetes, heart attack, and stroke.
- Our energy is low, and we’re not as motivated: Beyond what happens on a cellular level, individuals who sleep less are more likely to experience fatigue and sleepiness during the day, which may discourage them from daytime physical activity and promote more sedentary behaviors. This may lead us to take fewer daily steps, drag through or skip a workout, and simply push off the things that set us up for success—like cooking a homemade meal, hitting our water goals, or carving out time for that much-needed five-minute meditation session.
- We don’t recover from stressors—whether from life, work, or exercise—and we may stay stressed as a result: Sleep is when our bodies repair and replenish themselves to recover from all of the day’s stressors—from that work meeting that ran late to the hard workout you broke a sweat in. Lack of sleep is correlated with sustained elevated levels of cortisol—the hormone that regulates our stress response—which activates our “fight or flight” nervous system, also known as our sympathetic nervous system (SNS). Our SNS is what protects us from danger in short-term situations and is not meant to be “on” at all times.
- We have a harder time putting on muscle: Sleep is crucial for the process of building muscle—also known as muscle protein synthesis. Even short instances of sleep deprivation are shown to decrease muscle protein synthesis and, as a result, may lead to undesirable changes in performance and body composition. For individuals who engage in resistance training, getting adequate sleep is essential for maximizing and actualizing the benefits of strength training.
- We experience inflammation and our immune system takes a hit. We may get sick more often as a result: During sleep, certain components of our immune system rev up. Specifically, the production of proteins that affect the immune system—known as cytokines—increases, helping our bodies to fight off illness, infections, and inflammation. When we’re sleep deprived, our bodies produce fewer of these cytokines, leaving us with fewer defenses against illness and infection.
- Our gut health may suffer: Studies show that fragmented sleep and short sleep duration are associated with changes in gut bacteria and may contribute to gut dysbiosis—a state that describes an imbalance of good and bad bacteria in the digestive system. In one study, two nights of sleep deprivation were correlated with less gut bacteria diversity. Not only can a lack of sleep affect our gut, but poor gut health can affect our sleep, too.
How can we promote good sleep?
A disturbed sleep-wake cycle can give rise to future sleeping problems. Without proper signaling from the body’s internal clock, we can struggle to fall asleep, wake up during the night, or be unable to sleep for as long as we want to in the morning. (Cue the dreaded “I’m awake before my alarm” feeling!)
Staying in sync with our external and internal environments through proper sleep hygiene can help us score some high-quality Z’s.
Here are 11 ways to optimize your circadian rhythm:
Stick to a consistent sleep-wake cycle:
Aim to wake up and go to bed at the same time every day or within a 30-minute to 1-hour window, even on the weekends. Maintaining a consistent sleep schedule reinforces your body’s natural sleep-wake cycle and leads to higher quality rest.
Get sunlight early in the morning:
Research shows that getting natural sunlight 0-2 hours after waking positively impacts sleep duration and helps maintain regular circadian rhythms. In addition to exposing us to light, the sun provides the most potent form of vitamin D, which is involved in the production of melatonin.
Establish a regular exercise routine, but avoid exercise too close to bedtime:
Various studies show that regular exercise, including moderate-to-vigorous aerobic exercise in particular, has been shown to improve sleep quality and sleep onset (the time it takes us to fall asleep). Exercising outdoors, especially in the morning, may also improve total sleep time.
While the best time to exercise is whenever you can be consistent, high-intensity exercise one hour before bedtime or less may delay the time it takes to fall asleep and reduce sleep quality. Vigorous exercise increases core body temperature and heart rate and signals the stress hormone cortisol, which may interfere with the body’s natural production of melatonin.
As a general rule, avoid caffeine after lunch:
Studies show that consuming caffeine even six hours before bedtime can disrupt sleep. However, individuals who are “slow” caffeine metabolizers may need to cut off their last cup of Jo even earlier.
Aim to eat your last meal three hours before bedtime:
Make your dinner light and avoid refined carbohydrates and high-fat and spicy foods at night.
Consuming too many calories at night goes against our circadian rhythm and eating a large meal too close to our bedtime may contribute to acid reflux, heartburn, and indigestion.
While complex carbohydrates—carbs that contain fiber, are slower to digest, and are friendlier on our blood sugar—may improve sleep quality, high consumption of high glycemic carbs has been shown to increase insomnia risk by causing reactive hypoglycemia: low blood sugar that happens in response to large amounts of insulin the body releases after a high-carbohydrate meal.
And it’s not just carbs we should look out for. Consuming a high-carbohydrate, high-fat meal may delay glucose absorption even further as fat slows digestion, causing blood sugar levels to remain elevated for up to 5 or more hours.
High pre-bedtime blood sugar can lead to blood sugar imbalances, which may cause sweating or feelings of restlessness or agitation before bed, and increased bathroom trips during sleeping hours.
Being mindful of spicy foods at night is useful too as spicy foods may increase body temperature, which has been linked to poor sleep quality.
If you’re hungry before bed, choose specific sleep-inducing foods instead:
Going to bed with feelings of extreme hunger may decrease sleep onset and sleep quality, too. Aim to consume foods that are rich in complex carbohydrates and that provide natural sources of compounds that promote good sleep like melatonin, tryptophan, and magnesium. Ideas include a small banana with a tablespoon of unsweetened nut butter, a serving of Greek yogurt with sliced kiwi, a serving of cottage cheese with sunflower or pumpkin seeds, a handful of tart cherries, or a small piece of sprouted or whole-grain bread with sliced turkey.
Consider breaking the habit of habitually skipping breakfast:
Skipping breakfast often leads to a delayed eating schedule and, as a result, larger and later dinners. Eating earlier in the day better aligns our bodies with our circadian rhythm by signaling the end of a fast—hence the term “breakfast”—and the start of the day. And, for those who skip breakfast as part of a regular intermittent fasting routine, research shows that early time-restricted feeding in which individuals eat earlier in the day (from 8 a.m. to 4 p.m. instead of from 12 p.m. to 8 p.m. for example) supports balanced blood sugar and may improve metabolic health outcomes.
Dim the lights and avoid blue light from screens one hour before bedtime:
Light-emitting devices like cell phones, Kindles, and iPads prolong the time it takes to fall asleep and suppress melatonin levels. We get less rapid-eye movement (REM) sleep as a result. Aim to put a curfew on electronic use one hour before bed and use tools like blue-light blocking glasses or apps like f.lux to mimic natural daylight during daytime hours.
Cool your room before bed:
Regulations in our core body temperature are directly related to our circadian rhythm as our core body temperature dips slightly at night. Setting your thermostat anywhere between 60 to 67 degrees Fahrenheit helps the body regulate its temperature and signals that it’s time to go to bed.
Establish a relaxing bedtime routine and turn your bedroom into a sleep sanctuary:
High levels of stress increase the time it takes to fall asleep and fragments sleep. Unwinding before bed can help turn down the dial on our “fight or flight” response and activate our “rest and digest” mode. Yoga, breathwork, reading, journaling, stretching, or taking a bath are examples of relaxation techniques that tell your brain the day is over and sleep awaits. Environmental cues like soft lighting and uncluttered surfaces in your bedroom may also help you tap into tranquility.
Rethink your evening alcohol intake as a means to wind down:
While a nightcap can certainly induce feelings of relaxation and sleepiness, alcohol actually impairs sleep quality, reduces REM sleep, and reduces sleep duration. Alcohol is thought to interfere with melatonin and serotonin and can cause low blood sugar during sleep. If you enjoy an evening beverage, aim to consume alcohol at happy hour or with dinner, leaving plenty of time before bedtime.
What’s the best eating pattern for sleep?
A diet that supports our sleep looks a lot like a diet that supports other aspects of our health, like mood, focus, and immunity. Focus on whole, unprocessed foods that provide your body with all of the nutrients it needs to function optimally, like lean proteins, complex carbohydrates (carbohydrates with fiber, like starchy vegetables, potatoes, fruit, whole grains, and legumes), vegetables, and healthy fats like nuts and seeds. Research shows that deficiencies of certain nutrients, including vitamin D and omega-3 fatty acids, are associated with a higher risk of poor sleep quality, short sleep duration, and daytime sleepiness. Incorporating simple strategies like being mindful of meal timing and meal sizes and getting enough of key nutrients throughout the day are a surefire way to promote deep sleep.
What about supplements?
We recommend optimizing nutrition and lifestyle factors first. Resetting your circadian rhythm can be done, but it does take time and discipline. If individuals are really struggling despite these lifestyle modifications, supplements can be a useful tool to teach your body your new desired sleep schedule.
Dietary supplements, including melatonin, magnesium, valerian root, and L-theanine have all been studied to aid in sleep. To find out if supplementation is right for you, we recommend consulting with your physician or Registered Dietitian.
Takeaways and reminders:
While getting good sleep is one habit that we often put on the back burner, we know that prioritizing sleep helps to seal in all of our health efforts and improve outcomes across the board. When was the last time you slept through the night and awoke naturally, feeling refreshed?
If you’d like extra support in learning how diet and lifestyle changes may support your sleep and overall health, we’re here to help!
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