Links between diet and sleep
Wakefulness at night has become the new norm. The Mental Health Foundation recently conducted the largest ever survey of the UK’s sleep habits, revealing that up to a third of us suffer from severe sleep deprivation. However, getting enough quality shut-eye is vital for regenerating our minds and bodies. From effecting hormones and brain function the next day, to weight gain, depression and increased risk of acute and chronic disease in both adults and children, research shows poor sleep has both short-and long-term consequences for our health(1, 2, 3, 4, 5, 6, 7, 8,9,10). A review of 15 studies concluded people who don’t get enough sleep are at an increased risk of heart disease or stroke compared to those who sleep 7–8 hours per night (11). Meanwhile, individuals sleeping less than six hours per night have repeatedly been shown to be at an elevated risk of type 2 diabetes (12, 13).In contrast, adequate sleep boosts performance at work and in the gym and can help us with managing our food intake (14, 15, 16, 17).Indeed, food and sleep are intrinsically linked, each one influencing the other.
The scale of the problem
Obesity and sleep deprivation are two of the biggest health issues of our time, and it seems the two are related. Sleep-deprived individuals on average weigh significantly more than those who get adequate sleep (12, 13). In fact, insomnia is one of the strongest risk factors for obesity. One extensive review study showed children and adults with poor sleep were 89% and 55% more likely to become obese, respectively (14).
The effect of sleep on weight gain is believed to be mediated by numerous factors, including motivation to exercise (15). Sleep deprivation also disrupts daily fluctuations in appetite hormones, including higher levels of ghrelin, the hormone that stimulates appetite, and reduced levels of leptin, the hormone that suppresses appetite (16). This is believed to cause poor appetite regulation, cravings for high fat and high carbohydrate foods and increased calorific intake (17, 18).
A matter of time
Conversely, when and how much we eat can influence the quality and quantity of our sleep. Too much food too close to bedtime can cause acids and gastric juices to flow up into the oesophagus, resulting in heartburn that disrupts sleep. Some studies suggest late-night eating may also negatively impact the natural release of our key sleep hormones, melatonin and HGH (human growth hormone) (19, 20, 21, 22).
Drinking fluids too close to when we go to sleep can equally cause problems;nocturia (excessive urination during the night) affects sleep quality and daytime energy levels (23, 24). Although adequate hydration is vital for our health, it is advisable to reduce fluid intake 1–2 hours before bedtime to reduce the need to go to the bathroom overnight.
Drink to your health
What we eat and drink can also effect sleep quantity and quality. Small amounts of alcohol can help us fall asleep. However, as the body metabolises this, sleep may become impaired, especially during the rapid eye movement (REM) phase; the period of sleep when our body is in restorative mode. Alcohol can also cause dehydration, leaving us feeling lethargic the next day, and alter night time melatonin and HGH production (25, 26, 27, 28,29).
For some people, any food or beverage containing caffeine can disturb sleep. Caffeine acts as a stimulant on the nervous system and can stay elevated in the bloodstream for 6–8 hours, preventing our bodies from naturally relaxing at night. In one study, consuming caffeine up to six hours before bed significantly worsened sleep quality among participants (30). Therefore, drinking large amounts of coffee in the late afternoon and evening is not recommended, especially among those who are caffeine-sensitive or have trouble sleeping (31). If you do crave a cup of coffee in the late afternoon or evening, stick with decaffeinated coffee or tea, which is lower in caffeine.
Similarly, certain foods can hinder a good nights’ sleep; for example, those that are difficult to digest, are spicy or spike blood sugar levels. Therefore, avoiding these food groups before bed could help you drift off. On the other hand, consuming foods high in tryptophan, such as milk and oats, in the evening may aid sleep. Tryptophan is a precursor to serotonin, a natural sedative which enhances melatonin production. Meanwhile, carbohydrates facilitate the entry of tryptophan into the brain, vitamin B6 helps with serotonin conversion, and magnesium can improve relaxation and enhance sleep quality (32, 33, 34). In practice, this may look like a banana with a tablespoon of almond butter and glass of milk.
Many herbs are also reportedly useful for inducing sleep. Valerian is one of the most popular and its use as a sedative has been supported by research showing active ingredients in its root depress the central nervous system and relax muscles. Valerian brewed into a tea or taken as a capsule can reduce the time it takes to fall asleep and improve sleep quality.Take 500mg before bed (35, 36, 37) but check with your doctor before taking any supplements, and do not take if you are pregnant or breastfeeding. Other herbal remedies out there include teas made of chamomile, hops, lemon balm and peppermint, but there is not much scientific evidence to support their effectiveness.
Insomnia is being described as a modern-day health epidemic; it effects a large chunk of the UK population and has both acute and chronic implications. However, the fact that it’s very much linked to our lifestyles means we also have the power to tackle the problem. Whether it be cutting down on wine in the evening, on adding a little tryptophan-rich snack 1-2 hours before bedtime, small tweeks to your diet and day can make a massive difference. Why not give one of these a try tonight?!