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The Impact of Nutrition on Sleep

If you’ve followed M2 for long enough, you’ll know that we are big proponents of sleep.

Why do we care so much?? At a high level, there are a few obvious reasons: 

  1. The changes in hormones that accompany sleep are generally considered anabolic (muscle growing) (1). 
  2. One of the clear functions of sleep is tissue repair and most of this repair is thought to occur during the slow wave sleep phase, which is the deepest phase of sleep (2). 
  3. If your goal is performance, then both of these processes need to be major goals. Conversely if your goal is more aesthetic in nature, then you might be interested to learn that sleep restriction by as little as 2 hours leads to increased intake of both fat and carbs (3, 4, 5, 6).

The reasons we adore sleep go much further than this though, and as such we want to provide you with a full summary of the fascinating connections between sleep and nutrition AND how to use nutrition to improve your sleep.

Calorie restriction’s impact on sleep

When talking about calorie restriction and the impact that it can have on sleep, it is very important to keep in mind the demographics of people involved in each study. Below we look at the impact on sleep or lack of sleep in obese, overweight, underweight and healthy weight individuals

Impacts on people with obesity

At a high level, obesity can have severely negative impacts on sleep, and as a result long term weight loss will improve sleep quality (7). However, it is also well known that significant calorie restriction can disrupt sleep patterns, especially in early morning awakening (8). In the most extreme cases, people with anorexia have decreased rapid eye movement (REM) sleep and non-REM sleep (9). This phenomenon was also observed in obese patients as they lost weight, which indicates that the phenomenon has more to do with the hypo-caloric state, and less to do with total body fat percentages (10). 

Looking at the big picture, people with obesity will see long term improvements in sleep quality from a caloric deficit, however we have to be careful to not create too large of a deficit as the temporary DECREASE in sleep quality can lead to a myriad of issues including increased muscle loss, increased appetite, decreased cognitive function, etc.  In our experience, finding the right balance to allow for weight loss with minimal negative side effects on sleep is a very individualized process that takes some trial and error.

Impacts on people without obesity

When looking at non-obese individuals, the story is a little bit more complicated. In one study of 381 college undergrads, caloric restriction was linked to poor sleep quality and mood (11). However, it is worth noting that this study was observational and therefore the link might simply be a correlation and not a "cause and effect" relationship. Another small study perhaps provides more value as 10 women were put into a calorie deficit with multiple parameters studied over 4 weeks. The caloric restriction significantly altered sleep patterns, as sleep onset increased and slow-wave sleep decreased significantly. These changes correlated with decreased thyroid function (reduced T3 levels) indicating that calorie restriction may induce a hypo-metabolic state that affects sleep patterns (12).

In summary, if you're not obese, a calorie deficit is unlikely to help you have a good night of sleep and may instead lead to decreases in energy, mental alertness and physical performance. Tread carefully...

Impact of nutritional choices on sleep

There are near endless variables that one can study when examining the impact of nutrition on sleep. We’re going to try and break them down for you the best we can.

Carbs

A recent study examined the effects on sleep of four distinct isocaloric diets: a high protein diet, a (very) high carbohydrate diet, a high fat diet, and a control diet (13). The high carb intakes were associated with significantly shorter wake times, which the authors explained was likely due to alterations in serum serotonin levels leading to overall better sleep quality. Additionally, carb consumption has been shown to promote tryptophan entry into the brain (14). Tryptophan is a critical amino acid precursor for both serotonin and melatonin, two chemical messengers critically involved in sleep. As such, it appears that a higher carb diet may help improve sleep quality, though overall macro intake needs to be closely considered (15).

Protein 

A higher protein diet also appears to be helpful for sleep as well. Consistent protein intake, or what the authors called “habitual intake”, was positively correlated with sleep duration and quality (16). Another correlative study found that people who suffer from insomnia also tend to eat lower protein diets, but discerning whether low protein “caused” insomnia or vice versa was not clear (17). However, a separate study showed that a very high-protein diet reduced the number of wake-ups in comparison with a normal-protein diet (18) . 

Why might protein have these effects? Well, remember that protein is composed of 20 amino acids, one of which is called tryptophan. As I stated in the carb section, tryptophan is a precursor for a number of critical sleep factors. Notably, a low protein diet correlates with tryptophan depletion, lower serotonin levels and ultimately more waking periods compared to a normal protein diet (19). Finally, multiple studies show tryptophan supplement diets can improve sleep as well (20, 21).

Fat

There are two major studies that we can draw upon to understand the impact of fat on sleep. The first was an observational study, where a negative correlation between night time fat intake and the time it takes to fall asleep (also called sleep latency) was found in men but not in women. The same study noticed a reduction in REM sleep with the higher fat intake before bed (22). Secondly, a 2010 study found that total fat intake correlated with less sleep and more “subjective napping” (23). 

A few types of fat deserve additional attention, notably omega-3 and omega-6 fats, but let’s back up for a second. There are chemical messengers in your body called prostaglandins. Some prostaglandins impact sleep, specifically ones called PGD2 and PGE2. Prostaglandins are generated from omega-3 and omega-6 fatty acids. As such, appropriate intake of omega-3 and omega-6’s is necessary for appropriate levels of these critical sleep signals.

In fact, there’s strong evidence to suggest that omega-3 supplementation improves sleep quality. First is a study showing that DHA supplementation increases serotonin production as well as serotonin precursors. However the study was done in pigs and rats, which is a small, but important, caveat (24, 25). In humans, a study in children showed that 16-week treatment with DHA improved sleep quality as reported both by parents, and by actual formal sleep measurements (26).

 

In summary, dietary fats certainly are important for sleep but we have to be careful with 1) the types we consume and 2) when we consume them in the day. 

Final recommendations to improve your sleep with nutrition:

Putting this all together, I think there are some easy things we can do with our nutrition to improve our sleep quality.

  • Unless you are obese, eat to caloric maintenance and avoid long periods of caloric restriction.
  • Consume at least 1.6 g of protein per kg of body weight. Based on the studies listed, this amount meets the requirements for tryptophan production.
  • Avoid a very low carb diet.
  • Avoid consuming large amounts of fats before bed, specifically saturated fats (unless suffering from diagnosed narcolepsy).
  • Consider supplementation with omega-3s/fish oil, especially if wild caught fish is not a staple of your diet.