The average person spends a lot of time (about 30 percent of their life) sleeping. As crazy as that may seem, the third of our time we spend resting at night is incredibly important to making sure we are healthy and happy during our time spent awake. But in the same way, all of the habits and activities we engage in during the day inevitably have a big impact on how we sleep.
Some habits can be detrimental to our sleep quality and in some cases may induce insomnia or raise blood pressure, like drinking excessive amounts of alcohol, using nicotine, or ingesting caffeine late in the day. Others, like exercise and meditation, have been shown to increase sleep quality and duration.
The big picture answer is that diet does in fact play a role. Studies show that a person’s diet impacts how they sleep in a number of ways. This is likely due to the fact that what we eat directly affects important systems related to our sleep, such as brain chemistry, circulatory systems, and overall weight.
And what about popular beliefs about eating habits that harm or help sleep, like drinking milk or avoiding meals before bed? Read on to learn more about how changed to your diet can improve, or degrade, the quality of your sleep.
How diet affects sleep
Diet influences our nights the same way most other behaviors do: by causing changes to the circadian rhythm and the sleep cycle. The circadian rhythm is the body’s internal clock. An entire part of your brain is dedicated to keeping this clock running, always working to adjust our sleep-wake cycle according to external stimuli like light or sound. Some foods affect the circadian rhythm by triggering the production of chemicals in the brain that encourage or discourage sleep. Most foods that promote better sleep work in this way.
There are two main phases of the cycle: one in which your mind is more active, known as Rapid Eye Movement (REM) sleep, and a deeper sleep known as Non-REM sleep. Certain dietary habits can interrupt sleep by causing intense digestion or excess weight gain, which disrupts this cycle.
Foods that can promote sleep
Luckily for anyone interested in making changes to their eating habits to improve their sleep, studies show that a well-balanced diet is generally a good first step. A healthy diet can improve your night in two major ways: by promoting the synthesis of compounds that can improve the quality of your slumber, and by limiting the intake of foods that can interrupt it. Three chemicals, each playing a big role in the process, are significantly affected by diet:
- Serotonin: Serotonin is a neurotransmitter that helps regulate the circadian rhythm and sleep. Scientists are still working to understand all the complexities of the roles it plays, which include stimulating both wakefulness and arousal. One scientific review of over 50 years of serotonin research explains that serotonin is involved in starting, moderating, and ending these cycles.
- Melatonin: Melatonin is a hormone that plays an important part in regulating the circadian rhythm and promoting a restful night. Evening darkness stimulates the body to produce melatonin, which continues to build up in the brain through the night. Melatonin works in part by lowering core body temperature.
- Tryptophan: Tryptophan is a protein hormone that is the single precursor to serotonin. That means that in order to make serotonin, the body needs tryptophan. While the hormone can be produced internally, the body can also use tryptophan that is consumed in foods we eat.
Several foods can increase the natural production of these compounds or introduce more for the body to use. While all foods should be consumed in moderation, a 2016 scientific review found that including or substituting the following items into your diet can stimulate your body to produce the compounds it needs for a good night’s sleep:
- Milk: Milk products contain natural tryptophan. Several studies found that drinking a glass of milk or malted beverage before bed reduced awakenings, increased sleep time and promoted higher quality sleep.
- Kiwis/Tart Cherries: Cherries contain melatonin and kiwis contain serotonin, among other nutrients. Studies show that people who regularly consumed these fruits had less trouble going to and staying asleep, along with an overall better quality during the night. Note, however, that too much sugar could play a negative role.
- Whole Grains: Whole grains found in whole-wheat toast and oatmeal can trigger the production of serotonin. Johns Hopkins Medicine says that eating complex carbohydrates before bed can increase serotonin levels without burdening the digestive system late at night.
Diet habits that can degrade sleep quality
Scientists say that a sleep-promoting diet is more about having a balanced diet than eating or avoiding specific foods. That is, diets that are unbalanced in favor of a specific food group, especially if those foods are known to be unhealthy for other reasons, are likely to have detrimental effects on sleep health. High fat, carbohydrate and protein diets, in particular, have been shown to have adverse effects on sleep health. And importantly, they all influence sleep in different ways, suggesting again that a balanced diet is important for quality sleep.
- High-carbohydrate diet: Diets high in carbohydrates were correlated with less short-wave sleep. This type of deep sleep is part of the Non-REM phase. High carbohydrate diets do tend to improve REM when the brain needs more immediate energy for higher brain activity. But Non-REM is critical for the body to recuperate from the day, build muscle and bone, and boost the immune system.
- High-fat diet: High-fat diets have an effect almost inverse to high carbohydrate diets. Diets with high fat reduce REM and increase the number of arousals a person experiences in a night. However, a diet high in fat can also improve Non-REM. REM is important for mental alertness upon waking, and arousals can interrupt a good night’s sleep. High-fat diets can also lead to excess weight gain, which is associated with several sleep disorders including obstructive apnea.
- High-protein diet: High-protein diets, especially due to the consumption of meats, have been associated with negative sleep patterns. In a 2019 study, scientists suggest that a high protein intake can cause an amino acid imbalance in the body that disrupts its ability to synthesize serotonin from tryptophan. Protein is also difficult and time consuming for the body to digest, which can cause difficulty at night.
- Spicy foods: Johns Hopkins Medicine notes that spicy and acidic foods should be avoided 3-4 hours before bed, as they can cause acid reflux that is worsened by lying down.