How do I improve my sleep?
The importance of sleep cannot be overstated. Poor quality sleep is linked with impaired cognitive function, weight gain, reduced performance and an increased risk of many chronic diseases. It is well understood that dietary behaviours can affect sleep quality. Here I present the evidence regarding various dietary patterns/behaviours and their influence on sleep quality and offer advice on how to use nutrition to improve your sleep.
Macronutrients
Research suggests that the amount and type of macronutrients (protein, fat, carbohydrate) in your diet can have a major impact on sleep.
‘Unhealthy’ food
Unsurprisingly, consumption of a poor quality diet is linked with poor quality sleep. This study revealed that higher consumption of confectionaries, high-sugar beverages & fast food and low consumption of fruits and vegetables was linked with reduced sleep duration and quality. These findings are consistent with this study where a diet low in fibre but high in saturated fat and sugar was found to be associated with lighter, less restorative sleep.
Another study revealed that short sleep was associated with increased energy intake and decreased food variety – hallmarks of an unhealthy diet. This review concurs – finding that increased intake of fruits and vegetables, whole grains and other high fibre foods, and unsaturated fats (preferentially to saturated fats) was associated with decreased sleep onset (time it takes to get to sleep) and increased REM sleep.
Importance of carbohydrates and protein
The amino acid tryptophan may be of particular importance in this context. Tryptophan is an amino acid precursor to the sleep-regulating hormone serotonin and has been found to be important in the relationship between diet and sleep. Tryptophan is converted first to serotonin and then to melatonin, which is secreted at night by the pineal gland to induce and maintain sleep. It has been revealed that consumption of tryptophan containing foods – particularly in the evening - improved sleep in adults with sleep disturbances and enhanced alertness in the morning, most likely as a result of improved sleep quality.
This relationship may explain the efficacy of the old wives tale that ‘drinking a glass of warm milk will help you sleep’. The results of this review indicating that the consumption of milk (a source of melatonin) was associated with improved sleep quality.
There is likely a synergistic relationship between tryptophan and the hormone insulin. Elevated post-prandial insulin levels (after consuming a carbohydrate containing meal) have been shown to increase the brain’s responsiveness to tryptophan. This suggests that consumption of carbohydrate with proteins (particularly those high in tryptophan) may be the most favourable option with regards to optimal sleep. This association might explain the sleepy feeling one experiences after eating a turkey dinner (high in tryptophan) with potatoes (high in carbohydrates).
Clinical trials have echoed this idea. A low-carbohydrate diet was revealed to be associated with increased risk of insomnia. This is in accordance with other research that revealed a low-carb ketogenic diet to be associated with lower levels of REM sleep.
The above study found that consumption of relatively low levels of protein and carbohydrate was also associated with shorter, lower quality sleep.
Eating a balanced diet in line with the Eatwell Guide will likely optimise micronutrient intake and improve sleep quality..
Micronutrients
The effect of deficiency of various micronutrients on sleep are too numerous and complicated to go into specific detail here. Certain associations have been made regarding deficiencies in vitamin B1, folate, phosphorus, magnesium, iron, zinc, and selenium with shorter sleep duration. Delayed sleep latency (difficulty falling asleep) has been linked with lack of alpha-carotene, selenium, and calcium. Whereas insufficient intake of vitamin D, calcium and vitamin C has been connected to non-restorative sleep.
Consuming a balanced diet according to the Eatwell Guide is the best method of preventing nutritional deficiencies at the micronutrient level.
Other considerations
Caffeine
Caffeine has an extremely variable half-life inter-individual, which can range from 1.5-9.5 hours. This means that, in some people, if you consume a double espresso containing around 150mg caffeine at 2pm there may still be around 75mg caffeine in your system at 10-11pm – more than enough to disrupt your sleep, particularly sleep onset. If you are experiencing sleep issues I would highly recommend you consider the timing of your caffeine consumption. Consume your final cup of coffee (or other caffeinated beverage) earlier in the day and see if you notice an improvement.
Alcohol
Unfortunately, the evidence shows that alcohol will have a negative impact on sleep in both an acute and chronic setting. In an acute context studies reveal that, while alcohol is initially sedating, this effect disappears after a few hours resulting in a fragmented and disturbed sleep in the second half of the night. In a chronic setting alcohol abuse is linked with major sleep problems. This study found that high alcohol consumption was associated with poor sleep quality, reduced sleep duration and increased sleep disturbances.
Obesity
On top of the effects of an ‘unhealthy’ diet on sleep (described above), the body type associated with this type of eating behaviour may also exacerbate the issue. This study concluded that that central obesity (adipose tissue located primarily around the abdominal region) is associated with insomnia and/or obstructive sleep apnoea. These results confirmed previous trials that found weight reduction in overweight/obese subjects decreased symptoms of sleep apnoea and improved overall sleep quality.
Digestive Issues
Digestive issues can also affect sleep quality. However the affecting behaviours - and to what extent they impact an individual - can differ significantly from person to person. The best general advice I can give here is to maintain regular eating patterns, particularly with regards to your evening meal. This study revealed that a departure in a person’s natural eating habits will likely lead to poorer sleep quality.
If you are having significant digestive issues that are influencing your sleep there are meaningful methods of figuring out the problem and finding solutions. This is where personalised, individual help from a nutritionist like myself can be invaluable.
Bidirectional relationship
Research suggests that the relationship between diet and sleep quality is bidirectional – as diet affects sleep so may sleep affect dietary choices.
In this study of women (n=495) aged 20-76 poor sleep quality was associated with greater food intake and lower‐quality diet. A major review on the topic revealed an association between sleep loss and increased risk of obesity. This represents an opportunity for behaviours to spiral out of control. A poor diet leads to bad sleep - which leads to poor dietary choices and obesity – which further exacerbates the poor sleep – and so on…. This is a cycle that should be actively avoided.
What to do?
In short, In the absence of specific evaluation of your dietary behaviour, there are certain things you can do to ‘cover your bases’ and utilise your diet to improve your sleep.
1 - Eat a healthy, balanced diet - according to the Eatwell Guide and minimising consumption of highly processed, high sugar foods.
2 - Keep consistent dietary habits - if you are used to having dinner at 7.30pm a sudden switch to 9.30pm is likely not the best idea.
3 - Eat adequate protein – especially tryptophan containing foods
4 - Consume adequate carbohydrate - this will enhance the benefits of tryptophan. Don’t worry, eating carbs at night won’t ‘make you fat’.
5 - Maintain a healthy body weight
6 - Monitor your caffeine intake - the effect of caffeine varies significantly inter-individual.
7 - Avoid excess alcohol consumption
I hope that helps you get some much needed quality sleep!
Feed the life you want to lead,
Duncan