The Effects of Diet on Sleep
Quality sleep is essential for supporting brain function and physical health over the lifespan. While the effects of a bad night’s sleep can make us feel terrible the following day, poor sleep over time can increase risk for chronic health problems, including heart disease, kidney disease, hypertension, and diabetes.
Sleep Recommendations
Most adults should aim for 7-9 hours of sleep per night. This range is a recommendation; some individuals might function better when getting more than the recommended amount of sleep, while others may function normally on the lower end of this range. Sleeping less than six hours each night is not recommended for most adults.
Quality of sleep is just as important as the amount. Sleep consists of two basic phases: rapid eye movement (REM) and non-REM. Non-REM sleep is commonly known as deep sleep and is the phase where our bodies perform the most healing and rehabilitating processes. If you frequently wake up feeling unrested, you might not be getting enough non-REM sleep. A good night of sleep usually consists of 3-5 cycles of REM and non-REM sleep per night.
Diet and Sleep
Nutrition has an important effect on sleep quality and the body’s natural clock, or Circadian rhythm. Eating habits can impact sleep quality primarily by influencing neurotransmitters, hormones, and digestion. Neurotransmitters and hormones help control our sleep patterns, but they also influence all of the body’s natural processes.
Many processes are involved in sleep regulation, including the ingestion of nutrients, suggesting a link between diet and sleep.
Digestion slows down during sleep, causing food to sit in the stomach longer than usual. Eating calorically dense or large meals close to bedtime can disrupt sleep by increasing acid reflux symptoms and causing indigestion. Not only is it important to pay attention to what we eat before bed, but also when we eat during the day. Most evidence suggests that a consistent diet, eating the bulk of food earlier in the day, and avoiding eating late in the evening can improve sleep quality.
Hormones that Regulate Sleep Cycles
There are various neurotransmitters and hormones released by the brain that send signals to promote sleep or wakefulness. Many of these chemicals are stimulated by light or darkness.
GABA is a neurotransmitter that decreases nerve cell activity, playing a major role in allowing the body to sleep.
Adenosine is another neurotransmitter that gradually accumulates in the brain during the day, and at high concentrations makes us sleepy at night. Caffiene can keep us awake as it blocks brain receptors for adenosine.
Melatonin is a hormone released by the brain when it is dark. It travels to cells to tell the body to sleep. Sunlight or exposure to light inhibits the production of melatonin and increases the release of cortisol, which awakens us. If we are exposed to too much artificial light (such as the blue light emitted from smartphones or televisions) late at night, less melatonin may be released making it harder to fall asleep.
Serotonin, the body’s “feel-good” chemical, is a neurotransmitter associated with both sleep and being awake. The brain releases this chemical during daylight but also uses it to form melatonin at night.
Hormones that counteract sleep include norepinephrine, adrenaline, histamine, and cortisol. These are secreted in response to stress and cause the body to be awake and alert. If one experiences prolonged or chronic stress, the body releases adrenocorticotropic hormone (ACTH), which in turn releases cortisol. Levels of ACTH tend to be higher in people who have insomnia.
Appetite hormones: Sleep influences the appetite-regulating hormones ghrelin (the hunger hormone) and leptin (the satiety hormone). Poor quality sleep increases ghrelin and decreases leptin, which may result in increased hunger sensations with decreased satiety. When our body feels hunger, the brain signals us to grab foods that increase energy. Frequently, these foods are high in refined sugars and fat, which give a short-term energy burst. This usually results in energy spikes that cause us to feel hungry again sooner than usual and reach for more energy, which in turn leads to higher calorie intake. Research suggests that shorter sleep times are correlated with increased weight gain and waist circumference for all age groups. Sleep deficiency also increases one’s risk of developing obesity. The relationship between sleep and weight remains unclear, but a few mechanisms have been proposed to explain this relationship. (https://www.hsph.harvard.edu/nutritionsource/sleep/)
Nutrition Recommendations for Improved Sleep
Eat your last meal or snack a couple of hours before bedtime: Eating a couple of hours before bedtime will give your stomach time to digest food before going to sleep. As discussed above, sleep slows digestion, causing food to sit in the stomach longer and create more stomach acid. Though you may not be conscious of the impacts of indigestion while you are sleeping, you will likely feel the effects of a poor night’s sleep the next day.
Keep a consistent diet: Just as sleep contributes to the body’s Circadian rhythm, so does your diet. Eating close to the same time each day and making sure to have a healthy balance of nutrients will aid in aligning your body with its natural rhythm, which might in turn improve sleep.
Eat more during the daytime and less at night: As mentioned previously, when food is eaten too close to bedtime digestion will slow and lead to lower quality sleep. If the majority of food is consumed during the day when the body is still active, the majority of digestion can finish before sleep. Removing the need for digestion allows the body to focus on repair, restoration, and elimination of metabolic by-products during sleep.
Consume foods that improve sleep: If you need to eat soon before going to sleep, choose foods containing complex carbohydrates, such as oatmeal or whole grain bread Some research indicates that foods high in melatonin, tryptophan, and magnesium may help improve sleep quality. Dietary sources of each are listed below.
Melatonin – Eggs, fish, nuts, seeds, berries, tomatoes, and peppers.
Tryptophan – poultry (chicken & turkey), eggs, fish, milk, tofu and soy products, chocolate, and seeds.
Magnesium – Fish, nuts, seeds, legumes, fortified grains, spinach, and soy product.
Moderate caffeine and alcohol consumption: Caffeine is a stimulant. Stimulants disrupt sleep by blocking sleep-inducing hormones and increasing adrenaline production. Though consuming up to 250 mg of caffeine, or three 8-oz cups of coffee, a day is considered safe, the stimulating effects of caffeine may impact the body’s Circadian rhythm, making it harder to fall asleep, remain asleep, and enter deep sleep cycles. Caffeine can also create a harmful dependency cycle if left unregulated. Alcohol is a depressant. As a depressant, alcohol may increase adenosine (a sleep-inducing hormone) and help you fall asleep quicker. However, it also impacts the ability to enter deep sleep and remain asleep, causing poorer quality sleep overall.
A narrative review in the National Library of Medicine titled Effects of Diet on Sleep: A Narrative Review looked at research linking dietary intake and sleep outcomes. It found that the consumption of high carbohydrate diets, foods containing tryptophan, melatonin, and phytonutrients (i.e., cherries) indicated promising results for improved sleep quality and quantity, however further research is needed to understand the mechanisms underlying many of these effects; however, it is likely due to a dietary influence on serotonin and melatonin activity. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7230229/)
The takeaway: Whether you already have an established bedtime routine or are looking for new ways to improve your sleep, diet is an essential component to consider. Making a few small changes to your daily diet can improve sleep quality and promote good health outcomes.