PDF Summary:Sleep Smarter, by Shawn Stevenson

In Sleep Smarter, Shawn Stevenson asserts that high-quality sleep is the key to a healthier body, sharper mind, and overall increased quality of life. He provides a wide array of practical suggestions to help us achieve a good night’s sleep, incorporating nutrition, exercise, sleep habits, and aspects of our environment.

Stevenson is an educator, author, and professional nutritionist in the health and wellness field. He hosts the nutrition and fitness podcast “The Model Health Show” and also wrote Eat Smarter, a cookbook designed to help families eat healthier.

In this guide, we’ll explore the importance of sleep, the role of circadian rhythms, the impact of your sleep environment, and the unexpected benefits of sweet potatoes. In our commentary, we’ll explore more of the science behind why these strategies work, as well as some caveats when the research has produced mixed results.

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Habit #3: Get the Timing of Your Sleep Right

According to Stevenson, the timing of your sleep affects the quality of it. The best time to sleep—the optimal time for your body to make repairs and the time window in which your body is best able to produce the right hormones—is from 10:00 PM to 2:00 AM. During these hours, your body produces the most melatonin and human growth hormone (which helps your body stay youthful). If your sleep schedule isn’t aligned with the 10:00 PM to 2:00 AM window, you may feel unrefreshed and tired even if you got a full eight hours of sleep.

The process looks like this: Around 10:00 PM (a few hours after sunset), your body gets a natural boost of melatonin. This cues an increase in your internal metabolic energy, which is used for the repair processes we discussed earlier, including the production of antioxidants that protect your DNA.

This only works, however, if you’re asleep—if you’re still awake around 10:00 PM, you’ll feel a burst of energy, even if you were just tired. Instead of being used to rejuvenate your body while you rest, this energy goes toward waking activities like scrolling through your phone. You’ll probably have a harder time falling asleep when you get around to it, and you might wake up without feeling rested.

(Shortform note: The 10:00 PM to 2:00 AM window might not work for everyone. Some researchers assert that your best times for sleeping may be influenced by your chronotype, or your body's natural preferences for times to be asleep or awake. These preferences are widely distributed throughout society, appearing to follow a natural bell-curve distribution. Researchers have also found evidence that your chronotype may be linked to your genetics. One theory is that evolution selected for a distribution of sleep preferences to share responsibilities for keeping a lookout. If some wake up before others, and others stay up later than everyone else, that creates a wider window of time when someone is awake in the community should a crisis occur.)

The Best Bedroom Conditions for Sleep

In the last section, we explored how your body’s natural timing system affects your sleep. Now we’ll examine another factor that influences sleep quality: the environment of your bedroom. In this section, we’ll look at two changes you can make to your sleep environment: sleeping temperature and bedroom air quality.

Sleeping Temperature

Stevenson suggests that keeping your bedroom slightly cold can help improve sleep. This is because your body naturally cools down as you prepare for sleep, so if your body temperature is too warm, your body will remain in a state of wakefulness. By making your surroundings cooler, you're thus making it easier for your body to enter a restful state.

The ideal temperature for the room you sleep in is 60 to 68 degrees Fahrenheit (15 to 20 degrees Celsius). If the temperature in your bedroom is too far outside of this range—either too high or too low—you’ll likely have trouble sleeping. In addition to changing the settings on your thermostat, there are products such as cooling mattress pads that can help you keep your body at the ideal sleep temperature.

(Shortform note: Biologists have found that most mammals, including mice, cats, and chimpanzees, engage in thermoregulation—behaviors that maintain an ideal body temperature during sleep. These behaviors include building insulated nests, curling up into a ball, and huddling for warmth with other members of the species. Likewise, humans have been shown to subconsciously adjust skin exposure (rather than the thermostat) to maintain a consistent body temperature throughout the night, going under the covers to warm up and sticking out an arm or a leg when needing to cool down.)

Bedroom Air Quality

Stevenson states that the quality of air in your bedroom can also affect your ability to sleep well. He argues that you sleep better when breathing air that’s rich in negatively charged ions. These ions eliminate toxins and allergens such as mold, chemical gasses, dust, and pollen. The negative ions themselves also energize your body for higher performance of its regular chemical processes. However, when air sits around in a stuffy, enclosed environment, the ions in the air naturally lose their negative charge. Therefore, you can ensure the bodily health you need to get a good night's sleep by circulating airflow, either through a fan or open window, to keep ions from losing their negative charge.

Finally, keeping some houseplants in your bedroom can improve its air quality. Many common houseplants absorb toxic chemicals and release oxygen.

(Shortform note: Negative ions are atoms or molecules that have gained one or more electrons, giving them a net negative electrical charge. They are formed in nature by UV rays from the sun, thunderstorms, or the collision of water and air, such as in waterfalls or tidal spray. They can also be produced artificially through an electric ionizer. However, research into their health benefits has produced mixed results. Studies support Stevenson’s claim that ionization reduces particulate matter in the air. However, research has not found a strong link between ionization and improved respiratory health overall. More research is needed to conclusively understand their effects.)

Lifestyle Factors That Affect Sleep

In the previous section, we discussed multiple ways you can create an ideal environment for sleep in your bedroom. In this final section, we’ll look at common lifestyle factors that can change the quality of your sleep. First, we’ll explore the foods and beverages that can help and hinder your ability to sleep. Then, we’ll examine the relationship between exercise and sleep.

Foods and Beverages That Impact Sleep

Stevenson discusses how your dietary choices impact your sleep patterns and quality. Certain foods and drinks can either help to promote a restful sleep or disrupt it.

Caffeine

Stevenson names caffeinated beverages as one of the main offenders causing sleep disruption. While consuming caffeine isn’t inherently bad, doing so too close to bedtime—typically, within six hours of it—can interfere with your ability to fall asleep. To fully understand why caffeine is so disruptive, we need to first consider a chemical called adenosine. Your brain naturally produces adenosine when you're awake, and your nervous system regularly measures the amount of adenosine in your body to determine whether you've been awake for too long. The more adenosine your nervous system finds, the more tired it will make you feel.

Caffeine disrupts this cycle because it has a similar molecular shape to adenosine. It therefore connects with your body's adenosine receptors and blocks adenosine from triggering them. Therefore, your central nervous system "misreads" how tired you are, believing that you’ve been awake for less time than you actually have. This prevents you from naturally falling asleep when you're tired.

This creates a damaging cycle: Caffeine stimulates your nervous system and prevents the onset of natural sleepiness. After not sleeping well, you wake up tired, and you need to consume more caffeine to feel awake. Then, the high amount of caffeine you consume continues to disrupt your sleep, starting the loop over again.

(Shortform note: Despite its disruptive effects, caffeine consumption remains widespread. In the US, 93% of adults occasionally consume caffeine, while 75% consume it at least once a day. Furthermore, studies have found that most US adults don’t realize how much caffeine is in their beverages, and don’t know how much is safe to consume. While rare, some people have died from caffeine overdose, with children and those with pre-existing health conditions being the most vulnerable populations.)

Alcohol

Alcohol is another beverage to avoid before bedtime. Stevenson asserts that though alcohol may help you fall asleep faster, it hinders your ability to experience REM sleep. REM sleep is the stage in your nightly sleep cycle when you dream, and it’s a vital part of memory processing in your brain. Your brain needs REM sleep to prepare short-term memories for long-term storage. Without it, your memory and overall health will decline.

Additionally, alcohol can disrupt your sleep by increasing your need to urinate. Each time you get up to visit the bathroom, it breaks up your normal sleep cycle. The alcohol in your system then makes it unlikely you’ll get back into the right stage of sleep. To avoid alcohol-related sleep problems, Stevenson recommends stopping your consumption of alcoholic drinks at least three hours before you plan to go to sleep.

(Shortform note: While consuming even a moderate amount of alcohol can disrupt your sleep, heavy use of alcohol can lead to lasting sleep disruptions. One study found that chronic alcoholics can continue to have fractured sleep patterns for up to 21 months after getting sober. In other words, a lifestyle of alcoholism has the potential to keep disrupting your sleep for almost two years after putting down the bottle.)

Nutrients That Improve Sleep

Stevenson writes that a healthy diet can improve your sleep. He recommends getting nutrients from your diet rather than from supplements because your body can more easily recognize nutrients from whole foods. When vitamins and minerals are isolated in supplement form, they’re harder for your body to absorb.

(Shortform note: Some health experts provide additional reasons to prioritize healthy foods over supplements. Nutrients in food are often accompanied by additional nutrients such as carotenoids, flavonoids, and minerals that may not be found in supplements. Also, supplements are often less regulated than medicine and may contain other additives. Finally, many nutritional supplements are expensive, so simply choosing a healthier diet might be better for your financial health as well.)

Three nutrients in particular that Stevenson advises you include in your diet are tryptophan, vitamin C, and Omega-3s:

Tryptophan is necessary for serotonin production. You can get it from foods such as turkey, eggs, and sweet potatoes.

Vitamin C is important for staying asleep through the night. People who are deficient in vitamin C tend to wake up more throughout the night and generally have more sleep problems. You can get vitamin C from foods such as citrus fruits and leafy green vegetables.

Omega-3s contribute to sleep that is deeper and more restful. You can get omega-3s from foods such as salmon, chia seeds, and flax seeds.

Additional Benefits and Sources

Each of these substances has additional health benefits and dietary sources beyond those Stevenson lists. For example:

• Research has found that tryptophan plays a positive role in improving mood and cognition, and can help people who have inflammation-related health problems. It can be found in cheese, fish, milk, soybeans, and peanuts.

• Health experts assert that vitamin C supports your immune system and long-term cardiovascular health. It helps in maintaining healthy skin, blood vessels, bones, and cartilage, and helps with healing wounds. You can find it in broccoli and Brussels sprouts.

• Omega-3 plays a role in fetal development, cardiovascular health, and the prevention of Alzheimer's disease. You can find it in most fatty cold water fish, like mackerel and sea bass, as well as in kidney beans, edamame, and walnuts.

Herbal Supplements for Better Sleep

When you need a little extra help getting to sleep (and staying asleep), there are several herbal supplements that might help you. Stevenson states you shouldn't rely solely on supplements for sleep improvement, but certain ones can support and enhance the quality of sleep when used alongside other healthy lifestyle adjustments.

Kava kava is a plant from Fiji that’s typically taken as a tea. It’s a natural sedative and helps stop fatigue and sleeplessness. Research suggests that it may reduce the amount of time needed to fall asleep and improve the quality of sleep.

Chamomile is a common herbal remedy with many uses, including as a mild sedative. Drinking a cup of chamomile tea at night can help you fall asleep by relaxing your nervous system and releasing muscle tension.

Valerian is a stronger sedative. It helps you to fall and stay asleep. Its medicinal benefits come from the root, and it can be taken in tea, tincture, or capsule form.

Health Risks and Side Effects

Even herbal remedies, such as the ones Stevenson mentions, can have side effects and health risks:

Kava kava is traditionally a ceremonial plant used throughout the Pacific. However, research suggests it may be toxic to the liver, and it’s regulated in many countries, including Australia, Canada, Germany, Poland, and the UK. Furthermore, some researchers contend it has become a drug of abuse among Indigenous Australians, with destructive effects on their communities. If you use kava kava as a sleep aid, educate yourself on its effects and its legal status in your country.

Chamomile is generally considered a safe sleep aid. However, in rare instances, users may experience allergic reactions, particularly if they’re allergic to related plants like ragweed, chrysanthemums, or daisies. Chamomile may also interact with certain drugs like cyclosporine and warfarin, so talk to your health care provider if you are taking medication.

Valerian is widely considered safe, and relatively few side effects have been documented. However, research has linked Valerian to liver damage at high doses. One case study also suggests that frequent use could lead to withdrawal symptoms, including delirium. Use with caution.

The Exercise-Sleep Connection

Stevenson writes that sleep plays a key role in determining how effective exercise is for your body. This is because it’s only when you sleep that the positive effects of exercise materialize: During a workout, you create thousands of small tears in your muscles, which don't get repaired until you rest later, at which time your body produces hormones that repair these tiny tears. This repair process leaves your muscles stronger than they were before, leading to muscle growth—but it doesn't happen unless you get enough sleep to allow for it.

(Shortform note: Studies support Stevenson’s arguments about the importance of sleep to the body’s ability to repair itself, finding that the effect of sleep is so great that even brief durations of sleep deprivation—less than a week—result in reduced muscle mass in otherwise healthy individuals. Other studies have found strong correlations between chronic sleep deprivation and conditions like age-related muscle loss (sarcopenia), neuromuscular disease, and frailty.)

Sleep and exercise are positively correlated in the opposite direction as well—just as sleep benefits exercise, exercise benefits sleep. Stevenson writes, though, that what time of day you exercise makes a big difference in how much it improves your sleep, arguing that working out in the morning produces the greatest positive effects. This is because morning exercise encourages your body’s natural release of cortisol that helps to wake you up every day. This helps normalize your 24-hour sleep cycle, and thus, people who exercise in the morning typically sleep deeper and longer.

Stevenson advises not to exercise shortly before going to bed. When you exercise, you significantly increase your core body temperature, so if you exercise too late in the day, your body temperature may still be too warm by the time you want to go to bed. Exercising also induces the release of stress hormones that keep you alert, so it’s important to give yourself enough time for them to leave your system before bed.

How Do You Keep a Morning Workout Routine?

While working out every morning may help you get a good night's sleep, many people struggle to stick with their exercise routines. In The Power of Habit, Charles Duhigg offers some advice on how to make a habit stick. He argues that each habit requires three steps to become automatic:

1. The cue is an external trigger that tells you it's time to exercise. If you're working out in the morning, this could be your alarm clock going off.

2. The routine is the act that you would like to carry out, in this case, your actual workout routine.

3. The reward is the result of your routine that signals the end of the activity. If you find exercise intrinsically rewarding, you could just enjoy the feeling of accomplishment; otherwise, you could give yourself an external reward like a snack or an activity you enjoy.

Consistently adhering to this three-part cycle will make your morning workout routine easier to maintain, leading to improved sleep at night.