The World's Healthiest Foods

How do foods affect our sleep?

There's no doubt that there are many of us in the United States that have trouble getting a good night's sleep. The statistics here are striking. 42% of all healthy, middle-aged women report some kind of sleep trouble, including difficulty falling asleep, awaking during the night, or not feeling refreshed in the morning. For women 65 years and older, this percentage drops slightly to 30%, but the impact on other health problems may in fact increase. Even in younger age brackets, sleep problems are significant. Almost 17% of all 21-30 year olds report insomnia in research studies.

Sleep is a "Mind-Body" Experience

There's also no doubt that from a physiological standpoint, sleep is a complicated event and one that's related to many factors that cut across the "mind-body" spectrum. When we can't get to sleep because we're worried and feeling anxious, or depressed and feeling down, or confused and can't figure something out, we obviously aren't going to get to the root of our sleep trouble until we're able to work through the parts of our lives that we're feeling anxious or depressed about. At the same time, however, our nutritional status and the food we eat always influence our sleep. While we can't afford to overlook the psychological aspects, we also need to pay attention to the way we eat.

Patterns and Timing Make a Difference

We've all heard the advice, "don't eat a big meal too close to bedtime." Although this advice sounds simple, it's actually very important and not that easy to follow. On our World's Healthiest Foods website, we've tried to emphasize the sheer joy of eating healthy food. Getting to savor the aroma, and taste, and visual beauty of food is a part of what it means to be healthy. Many of us eat a meal late at night - within 2 hours of bedtime - precisely because we haven't made time during the day to enjoy food. In fact, we let ourselves get so hungry that we don't really care any more about the joy of eating. We just want something in our stomach! Research shows that the timing and size of our evening meal is closely related to the timing and size of our other meals throughout the day. When we have a cup of coffee in the car on the way to work, grab a sandwich for lunch or take care of all the household chores before getting around to dinner, we are setting ourselves up for a bad night's sleep.

Sometimes we rationalize and think that a big meal will actually help us get to sleep by exhausting our body and having it slow down from exhaustion as it tries to digest the large meal. It's tempting logic, but research evidence points in the opposite direction. A large meal does the opposite of slowing our body down. It asks our circulatory system to move more blood to our digestive tract. It asks our stomach to secrete more gastric acid. It asks our pancreas to become more active and produce digestive enzymes. It asks the smooth muscles around our intestines to become active. In short, a large meal does anything but relax us. In addition, our digestive tracts are set up to work best when we are standing; lying down results in gravity pulling the

"wrong way" to help food digest. Even though the practice of napping after a meal is common, it isn't ideal from the standpoint of digestion. Sitting and resting are fine. For example, enjoying each other's company around the table after a delicious meal is a good idea. But lying down to sleep just doesn't help digestion.

It's also worth thinking about the physiological purpose of eating in regard to late-night meals. Nutrients and energy get released from food after we eat, not before. They help increase our vitality hours after the meal has been eaten; they cannot go back and compensate for a prior day's worth of activity that received no nutritional support. The time to have our largest meal is always before we need the most nutritional support, i.e., before we have the most physically demanding part of our day. Sleep is the least physically demanding part of the day, and the least logical target for release of food energy and nutrients. We tell ourselves we've had a hard day, and we're starved, but at this point, it's too late to repair the nutritional damage. We need the nourishment before the hard day, and hopefully it will make the day less difficult!

We should also mention the problem of going to bed actually hungry; this other extreme also interferes with sleep, usually by failing to keep the brain supplied with enough glucose (sugar). A small snack in the hour before bed is usually not problematic if you are truly hungry, but the ideal solution is to time your last meal so that you don' feel hungry during the 1-2 hours before bed.

Food Stimulants

Some components of food, such as caffeine, artificially wake us up, so it makes no sense to have stimulant-containing foods before bed. Unfortunately, this applies not only to caffeinated coffee, but to all caffeine-containing foods, and to theophylline-containing foods (like black tea) as well. Chocolate and many soft drinks (including diet soft drinks) have substantial amounts of caffeine. An ounce of chocolate can contain from 10-60 milligrams of caffeine, and a soft drink will usually fall into this same range. Brewed coffee can have over 100 milligrams per cup, depending on the grind and brewing time. Eliminating these foods from your evening meal routine is recommended for improved sleep.

Although alcohol acts in the opposite way - as a depressant that slows down our nervous system activity - it has also been shown to interfere with the quality of sleep.

Serotonin, Food and Sleep

The hormone serotonin is an important factor in triggering sleep. Since our nerve cells use the amino acid tryptophan to make serotonin, much attention has been given to the role of tryptophan (and tryptophan-containing foods) in promoting sleep. First, we don't recommend increased intake of high-tryptophan foods as a way of improving your sleep. Second, studies of tryptophan's impact on sleep have found that it is only one phase of sleep - the falling asleep part - that is enhanced by tryptophan. Other aspects of sleep, such as the amount of deep-sleep reached during the night, are actually harmed by supplemental tryptophan.

Researchers typically divide sleep into two basic types, REM and non-REM. REM stands for rapid eye movement, and it's the phase of sleep that corresponds to dream sleep. Non-REM sleep has four stages, and we typically move through these four stages into REM in about 90 minutes. This 90-minute period is called the sleep cycle. In healthy sleep, we experience 5 or more sleep cycles per night, and the length of the REM phase increases as we move from one cycle to the next. Supplemental tryptophan gets us into the non-REM stages of sleep more quickly, and in this respect can be helpful with insomnia. At the same time, however, tryptophan has been shown to increase non-REM sleep and decrease REM sleep - a non-desirable outcome in most situations.

Many animal foods are relatively high in tryptophan and might sound like logical candidates for improving sleep because their tryptophan could be used to produce serotonin. However, these same animal foods are also fairly high in other amino acids (like tyrosine) that could be used to produce other regulatory substances (like adrenalin) that would usually decrease with the onset of sleep. In summary, we don't recommend trying to up your serotonin by increasing your evening intake of high-tryptophan foods as a way to improve your sleep.

Our serotonin levels respond to other aspects of our diet, however, and one of those aspects is carbohydrate intake. Eating foods higher in carbohydrates raises our blood insulin level. This is because carbohydrates are digested relatively quickly and raise our blood sugar level more quickly than proteins or fats. Along with this increased insulin level there is an increased transport of amino acids into our brain, including tryptophan. More brain tryptophan leads to more brain production of serotonin and increased likelihood of sleep onset.

This line of thinking has been explored by researchers Richard and Judy Wurtman at the Massachusetts Institute of Technology, particularly with respect to carbohydrate-craving during depression. With respect to sleep, our conclusion would be: if you're going to eat a snack 1-2 hours before bed, a small carbohydrate-based snack that includes some protein and some fat would make the most sense. This snack could be a slice of whole grain bread with a little almond butter, or a 1/2-serving of our website Perfect Oatmeal.

Food, Sleep and Exercise

In many studies, and in our own practical experience, being physically tired from a healthy day's activity - including morning, mid-day, or early evening exercise - is one of the best promoters of a good night's sleep. We can be mentally exhausted from the day, but if our body is not physically tired as well, it may not feel ready for a night's rest. Exercise helps regulate our appetite just as much as it helps regulate our sleep. When we're active, moving and placing physical demands on our body, it gives our body a healthy context for deciding when food is needed and when it is not. Even if it's simply a twenty-minute walk, coordinating our meal plan with an exercise plan is a huge plus when it comes to sleep. Food, sleep and exercise are three components of our life that are meant to work together. Replacing your lunch hour with an exercise hour does not make sense, any more than skipping a walk to provide a more leisurely dinner. For healthy sleep, we need to plan our day so that both components get included.

Overall Nutrient Supplies and Sleep

The complex nature of sleep means that all nutrients - including amino acids, fatty acids, vitamins, and minerals - are needed in optimal amounts to support the sleep process. Some of our most important immune system functions occur only during sleep, as well as some of our most important "antioxidant balancing" activities. On this website, we list literally dozens of food components that act as antioxidants, and we explain how specific vitamins and minerals support immune function. Sleep requires many nutrients to support a very complex process so the World's Healthiest Foods strategy of enjoying nutrient-dense foods will also help you get a better night's sleep. It will also allow you to relax and enjoy the pleasure of real food.

Note: (For additional information on sleep, you may want to visit the following websites: www.sleepnet.com, www.sleepohio.com)

Practical Tip:

What should I eat to help me sleep?

Not too much! It is important that your body be able to focus on rest and repair while you sleep, rather than on digestion. It is more important to gear your evening meal towards relaxation and good digestion than to consume any particular food or drink before bed. Try some of our delicious, easy to prepare recipes, for a healthy promoting evening meal. Your evening meal should:

Your evening meal should be eaten about 4 hours before bedtime so that the main digestive effort is finished, but the energy from these foods can be released gradually throughout the night. If it is necessary for you to eat a snack at bedtime, choose one or two of the following:

References

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Hayes MJ, Parker KG, Sallinen B, Davare AA. Bedsharing, temperament, and sleep disturbance in early childhood. Sleep 2001;24:657-62.

Moldofsky H. (1995). Sleep and the immune system. Int J Immunopharmacol 17(8):649-654.

Newman AB, Enright PL, Manolio TA, Haponik EF, Wahl PW. Sleep disturbance, psychosocial correlates, and cardiovascular disease in 5201 older adults: the Cardiovascular Health Study. J Am Geriatr Soc 1997;45:1-7.

Owens JF, Matthews KA. Sleep disturbance in healthy middle-aged women. Maturitas 1998;30:41-50.

Reynolds CF 3rd. The implications of sleep disturbance epidemiology. JAMA 1989;262:1514.

Wetter DW, Young TB. The relation between cigarette smoking and sleep disturbance. Prev Med 1994;23:328-34.

Wurtman RJ, Wurtman JJ. Brain Serotonin, Carbohydrate-craving, obesity and depression. Adv Exp Med Biol 1996;398:35-41.