Many of us experience periods where we struggle to get any decent sleep. For some of us, this can be a troublesome problem that persists, causing daytime fatigue, loss of concentration, irritability and can even impact upon our weight. This article explores the mechanisms behind sleep, and how food may help us improve our sleep quality.
Sleep, or desire to sleep, is regulated by cycles known as circadian rhythms, which are driven by our internal body clock. For most of us, this gives us a stronger desire to sleep between 2-4am and between 1-3pm (often known as the afternoon “dip”). Our circadian rhythms also impacts on many other body systems too: how and when we metabolise foods, hormone regulation such as cortisol, our blood pressure and heart rate among others. One of the important aspects for sleep that circadian rhythms influence is a hormone called melatonin, which is produced by the pineal gland, found between the brain and the brain stem deep within the cranial tissue. Melatonin release is regulated by light, and so it rises at night-time and stays elevated until daylight appears. Working with circadian rhythms, melatonin influences our sleep-wake patterns.
Poor sleep could lead to bigger appetites (due to a response from a hormone called leptin, which controls our appetite), which may result in weight gain. Weight gain affects sleep if it contributes to snoring, sleep apnoea, night-time heart burn called reflux (when acid is displaced from the stomach into the gullet as we lay down) and so we can easily be locked into a vicious cycle.
How food can help sleep
There have been a number of studies around nutrition and sleep, but none can confidently tell us that any particular food or diet helps sleep. You will see from this article how complicated the area of sleep and nutrition is, and how much of the advice really is experimental. We will look at some interesting theories and study results that do appear to work for some people when trialled against a control, so if you have trouble with good quality sleep then why not give some of these tips a go? You could be one of those people it works for. Try any or all of the ideas we will cover.
Foods with tryptophan
One theory is that eating foods rich in tryptophan, an amino acid that is used by the body to make melatonin (via serotonin), might enable better sleep. Tryptophan is a tricky thing to get through the blood-brain barrier, where it is used to create melatonin. The reason for this is that many other amino acids want to get across the blood-brain barrier too, and this barrier is so well-regulated that it’s very fussy what can get passed and when. Tryptophan is one of the least abundant amino acids in our diet and therefore has very strong competition from other amino acids to get across this barrier. Therefore, the theory is, if you increase the tryptophan in your diet, you give it a better chance against the other amino acids of getting passed this barrier so it can then convert to serotonin and then to melatonin, which then helps you to sleep!
Foods particularly rich in tryptophan include:
– Soy protein such as tofu
– Cheese, particularly mozzarella
– Nuts and seeds, particularly pumpkin seeds
– Poultry, particularly chicken and turkey
Foods with melatonin and serotonin
Eating foods high in tryptophan is problematic because first you need to ensure tryptophan makes it to the blood-brain barrier in tact (and hasn’t been converted to something else beforehand). Once there it needs to get passed it, then you have to convert it to serotonin and then to melatonin! That’s a lot of steps, so why not just consume foods that have natural sources of these hormones? Surprisingly, there are many different foods that naturally produce these hormones, so that cuts out the middle man right? Possibly not, firstly it’s not actually proven that the melatonin or serotonin in foods is easily available to us, and when it is, does it get to where it needs to in order to promote sleep? Some studies suggest that they’re metabolised before they have chance to have their intended effect. Serotonin cannot get through the blood-brain barrier but melatonin can, however the methods used to measure melatonin in foods gives very wide ranging results. That said, there are a few studies that show melatonin-containing foods may help with sleep in some people.
Foods with melatonin include:
– Tart/sour cherry juice concentrate
– Tart/sour cherries
– Kiwi fruit
Carbohydrates and sleep
Carbohydrates are required to help tryptophan get across the blood-brain barrier and then convert into serotonin, but too much of them can impair our sleep, particularly if we eat them late at night. Eating carbohydrates raises the hormone, insulin; insulin impairs “slow wave sleep” quality and reduces the production of growth hormone. To improve sleep quality, therefore, you need to avoid foods that increase insulin before you sleep, such as sugary foods. It has also been found that a diet high in saturated fat and low in dietary fibre could impact sleep in just one day! So eating a fatty take-out meal could impact your sleep quality that night, making you feel drowsy and less fresh the following day.
If you have difficulty with sleeping, try a diet higher in protein and dietary fibre (complex carbohydrates that don’t impact on blood insulin so much) and see if that changes your sleep quality. Some research suggests that eating carbohydrates after you’ve eaten a meal high in tryptophan protein works well, but you’d have to make sure it’s a complex type such as a wholegrain snack.
General dietary advice for good sleep:
Avoid drinking or eating caffeinated products after 3pm, such as coffee, tea, chocolate and energy drinks.
- Alcohol disrupts sleep, so if you drink every day, consider reducing days you take alcohol.
- Don’t use melatonin pills that are available on the internet as these can disrupt your own natural capability of producing melatonin.
- Avoid sugary foods late at night, and keep caffeinated products for the morning.
- Warm milk before bed has both tryptophan and carbohydrates – worth a go!
Seb is a writer and blogger of food and nutrition. He holds a bachelors and a masters degree in nutrition science, and has studied sports and exercise nutrition at postgraduate level. He specialises in plant-based nutrition and believes passionately that we can all live with a little less meat.