Improve your sleep; improve your health

Good quality sleep is essential for good health as it impacts metabolic, emotional and cognitive processes. Given that sleep problems affect one in three adults and have been linked to the leading causes of death such as cancer and heart disease, it seems that the need to improve sleep is a ‘no-brainer’.

The link between sleep and nutrition

We have long known that your sleep is affected by your food intake. Likewise, sleep affects your dietary intake and nutrition, and short sleep has been linked to obesity. (See my post Getting a good night’s sleep in 9 ways. ) Because of the importance of this relationship, more and more researchers are looking at the effects of manipulating macronutrient intakes (proteins, fats, carbs) on sleep outcomes. Here’s a recent report.

Review of the scientific literature

This 2021 study is a systematic review and looks at the effects of macronutrients on sleep improvement, in order to provide dietary recommendations for better sleep. 

A research study was included in this review if it:

1. delivered a macronutrient-based dietary intervention;
2. included healthy adults aged 18 and older; and
3. measured some aspect of sleep, for example, duration, quality, difficulty sleeping or snoring. 

A total of only 19 studies met the above criteria (note: this is not a lot). The 19 studies were organised into:

• acute studies lasting less than a night (there were 4 of them)
• longer-term studies (more than a night ranging from 2 days to 3 weeks) (10 studies), and
• energy restriction studies for overweight people (5 studies). 

The four stages of sleep

To understand the results of the review we need a quick overview of the four stages of sleep. The first three are categorized as non-REM (Rapid Eye Movement) Sleep and the fourth is REM sleep.

1. The first stage of non-REM sleep is when we move from being awake to being asleep.  This stage is short and usually only lasts a matter of minutes. The sleep is light, your breathing and heart rate slow and your muscles begin to relax.
2. During the second stage of non-REM sleep your breathing and heart rate slow further, and your muscles relax more. Your eye movements stop and your body temperature drops.  Your brain wave activity slows down except for occasional bursts of electrical activity.  Stage 2 sleep is where you spend most of your repeated sleep cycles.
3. Stage 3 of the non-REM sleep is sometimes referred to as Slow-Wave Sleep (SWS), delta sleep, or deep sleep. Stage 3 non-REM sleep is believed to be critical to restorative sleep. It is during this period that bodily recovery and growth occurs. It is also thought to be important for the immune system. 
4. The fourth stage of sleep is REM sleep. This is where are your eyes move rapidly and where you experience the dreaming state. The brain wave frequencies become mixed and are similar to those experienced while you are awake. Breathing becomes faster and irregular, and your heart rate and blood pressure increase similar to waking levels.  During REM sleep your limbs become temporarily paralysed which stops you from acting out your dreams. As you get older you have less REM sleep. 

What the review found 

The review found that short sleep was associated with greater energy (kilojoule/Calorie) and fat intake “as well as increased snacking and inadequate micronutrient intake, particularly calcium, vitamin D, and magnesium”. 

The results which most positively influenced Rapid Eye Movement (REM) sleep were observed for longer-term administration of higher carbohydrate diets. This means carbs ranging from 56 to 80 per cent of energy intake. So, for a standard 8,700 kJ (2200 Cal) diet, this translates to 280 to 350 grams of carbs a day (14 to 17 slices of bread). 

However, higher carb diets also negatively influenced Non-REM sleep which led to overall neutral findings for sleep.

The higher protein diets, under conditions of energy restriction, for weight loss did improve sleep quality. Weight loss of any sort has long been linked to better sleep duration and quality but this can also interfere with any results.

Four out of the five studies changing the quantity of protein or carbs eaten while holding fat constant reported beneficial effects on sleep quality.

The study reported that it does not support the effects of short-term meal-based interventions, less than a night, on sleep outcomes. You can’t affect your sleep in just one night – you have to manipulate your overall diet for at least a couple of nights before you can see any sleep benefit at all.

The bottom line 

The science is not yet ready to make public health recommendations. The researchers concluded that the sleep interventions were highly varied and shortcomings to all the methods were identified (small sample size, imprecision, gender imbalance, heterogeneity, high risk of bias). More work is required to fully understand how macronutrient intake affects sleep outcomes. However, for now, losing weight, it seems, can help you get higher quality sleep.