Nutrition plays a role in our sleep and vice versa. That much is obvious.
But the bigger questions are:
- How much impact can it have?
- How much impact is it likely to have on the average person?
- What if you are not average and you have some clear gaps/issues?
This post will cover a lot of those aspects. It will also cover specific areas to focus on to achieve these benefits.
But one of the reasons I have held off on writing about this topic for a while is because it is so broad. There are so many variables. To get past that, I am going to try and cover a lot, BUT also be okay with leaving some stuff out. Just because I have not mentioned something, does not mean I do not believe it plays a role. I am just trying to cover a lot of the key aspects that seem to matter a lot or are talked about a lot.
A Note on the Bi-Directional Relationship Between Sleep and Food
Everybody knows sleep is important. But if you are trying to achieve stuff with your nutrition, it really helps if you get good sleep.
Firstly, there is research showing that if you give two groups the same diet and exercise but one group gets significantly more sleep, the group getting more sleep makes a better fat loss and/or muscle gain progress.
A great thing about that research is it shows sleep is important even if you control for other variables.
In the real world though, those variables are impacted by sleep. People who sleep less typically consume more calories and lower-quality diets in general.
This can be because a lack of sleep can contribute to increased hunger and cravings. Or maybe it is because being awake for longer means you have time to eat/snack. Or it could be because when people are tired, their goals suddenly seem less important. There are a lot of factors.
Either way, it can be a bit of a cycle. Good sleep makes good nutrition easier. Good nutrition can also make good sleep easier.
Let’s start with the obvious. Caffeine is well known for disrupting sleep.
Caffeine blocks adenosine receptors. Adenosine is a sleep-promoting chemical, so it is easy to see how it has this effect.
The average half-life of caffeine is 5 hours. But this can range from 1.5-9 hours depending on the individual.
Based on the average, you can see why it is common advice to stop consuming large amounts of caffeine from either 12pm or 2pm, depending on who you listen to.
There is clearly individual variation though. If you are a rapid metaboliser of caffeine, you could be fine having it a bit later in the day. But somebody who is a slow metaboliser would need to stop quite early in the day.
Another sometimes overlooked aspect is uncommon sources of caffeine. For example, tea, chocolate and Coca-Cola all have caffeine. They do not have as much coffee, but they do have some. If somebody was particularly sensitive to caffeine, this could be an issue if consumed late in the day.
Carbohydrate Intake and Timing
Carbohydrate intake is an interesting area in sleep research.
Right now, the research seems to indicate that higher carbohydrate intake seems to outperform lower carbohydrate diets in terms of sleep duration and quality. In particular, there appears to be more time spent in REM sleep.
This effect is even more noticeable when a higher carbohydrate meal or snack is consumed 1-4 hours before bed. It seems to reduce the time it takes to get to sleep as well.
I need to add some caveats here though:
- The research I have seen does not really cover low-carb diets and their effect on this. When I say “lower” I am referring to a lower amount than the high carbohydrate comparisons. It still is not what most people, including myself, would define as low carb.
- The impact of this is not huge. It is relatively minor. We are talking about like 10% improvements in time to get to sleep and also total REM sleep.
- There is individual variation here. This research is just identifying what happens on average.
- Because the effect is small, it should not really outweigh other factors. For example, if you have a medical condition like diabetes and you are managing that in a way that involves consuming a certain amount of carbs, you probably should not change that for these purposes.
- There is research indicating that time-restricted eating does not have much impact on sleep duration or quality. That often involves not eating within the few hours before bed, so it adds to the argument of that pre-bed meal/snack not being super important.
Being Overly Hungry/Full
As a point that adds to the previous section. Some people really struggle to sleep if they are either overly hungry or full.
The research on indicating that a high-carb meal 1-4 hours before bed becomes less relevant for somebody who feels that negatively impacts their sleep. Particularly if other variables like reflux are involved, which are exacerbated if lying down too soon after food.
Alternatively, the research showing that time-restricted feeding does not really affect sleep is also less relevant if somebody feels starving if they have not eaten in a few hours, and that happens to disrupt sleep.
Listening to your body in either of those situations is important.
Tart Cherry Juice
Now we are into the more interesting stuff. This one is the first hack/strategy that you can use to see a significant improvement.
Tart cherry juice has a lot of research supporting the role it can play in improving sleep.
The mechanism behind this is likely due to tryptophan and melatonin.
Tart cherries contain tryptophan and there is also evidence that they lead to an increase in melatonin* production in the body.
Consuming tart cherry juice ~1-2 hours before bed also has the additional benefit of ticking the box from that carbohydrate perspective discussed earlier.
In terms of outcomes, some of the most promising research has shown as much as an average increase in sleep time by 85 minutes in those with insomnia.
Obviously, not all the research is THAT promising. But it does consistently seem to improve sleep.
* I won’t be discussing melatonin supplementation in this article. It is something that can help with sleep. But in Australia, properly dosed melatonin is only meant to be accessed via a prescription. Because of that, I’m leaving it out of this as a separate category from nutrition, even though it can help.
Fibre, Saturated Fat and Sugar
Low fibre, high saturated fat and high sugar intake are associated with less deep sleep and more frequent awakenings.
There are a lot of potential explanations for this. But it is also worth noting that those things can be a bit of a proxy measure of dietary quality in general.
Those things are typically the opposite of what is traditionally considered a healthy diet.
Somebody doing those things likely has a lower micronutrient intake for example. They likely consume more calories too.
Is it those specific variables causing the sleep disruption? Or is it other variables that are likely involved due to those factors being present? Stuff like this is always difficult to interpret in nutrition research like this. But it is worth being aware that there appears to be a link.
For context, in this study, when they compared the high saturated fat intake to a mixed meal with less saturated fat and more protein, the participants fell asleep 15 minutes quicker. That is probably enough of a difference for most people to care about.
Ashwagandha is an herb that is often used in Ayurverdic medicine.
It is an interesting option because a lot of the research on Ashwagandha typically looks quite promising.
For example, a randomised controlled trial found that people who took Ashwagandha for 6 weeks self-reported their sleep being 72% better than at baseline. For context, the placebo group reported a 29% improvement.
The theoretical reason ashwagandha helps sleep is that it helps reduce stress and anxiety.
Unfortunately, there is not a lot of research on it. It is not like there is no research. There is a small amount, and it is mostly positive. But less than I would like.
Based on that mechanism, I would assume that those who feel stressed or have anxiety are more likely to benefit from Ashwagandha than those who do not.
Another option in that stress and anxiety improvement category is L-Theanine.
It does not directly do anything to improve sleep. But the research on it and anxiety and stress is quite promising.
There is also research showing that those who are likely to benefit from that effect are also likely to experience improved sleep.
Clearly, Ashwagandha and l-Theanine are not relevant for everybody. They do not directly improve sleep, it is an indirect effect. But if stress and anxiety are playing a role in your sleep, which is the case for a lot of people, it could be worth looking into this area further.
Magnesium and sleep is a super interesting topic since it is one of the most commonly mentioned options, but the research is actually a bit less promising than you would expect.
The mechanism makes sense. Magnesium binds to GABA receptors. And GABA is a neurotransmitter that helps your brain wind down.
It is also clear that magnesium deficiency impacts sleep negatively.
The tricky thing is the main positive research I am aware of on magnesium and sleep is on those with insomnia. It does seem to help in that case.
But what about somebody who just wants to improve their sleep, but doesn’t have insomnia?
I have not actually seen much research indicating that it improves sleep noticeably there.
Anecdotally, the majority of people I have heard from who track their sleep quality in some way self-report magnesium improving their sleep quality. So that is worth being aware of. But it is interesting that it is so commonly recommended but does not have much strong research supporting it.
It is also worth being aware that it is quite common for people to have a sub-optimal dietary magnesium intake as well.
I am of the mindset that if you like doing it, you do not notice any downsides and you also feel like it helps, it probably makes sense to continue.
Small amounts of alcohol often make people feel relaxed and, in some cases, might even help people get to sleep quicker. This effect appears to diminish if done consistently though.
Large amounts of alcohol obviously disrupt sleep quality, however. But even more moderate amounts such as a couple of standard drinks likely reduce sleep quality a bit by reducing the amount of REM sleep.
It could also potentially increase the impact of sleep apnoea in those affected by it too.
The Effects of Longer-Term Calorie Deficits on Sleep
Being in a calorie deficit can play a role in sleep in a few ways.
A calorie deficit leads to weight loss. So if you happened to have your sleep is impacted by your weight (it may or may not be playing a role in obstructive sleep apnoea for example), then a calorie deficit could potentially help your sleep.
Alternatively, if somebody was already pretty lean, being in a calorie deficit for an extended period of time likely negatively impacts sleep noticeably. This is particularly prevalent in the world of bodybuilding where people get down to exceptionally low body fat percentages towards the end of comp prep.
Large calorie deficits in general also lead to more difficulty getting to sleep. They appear to reduce the amount of deep sleep people get too.
For those who are overweight/obese and have impacts on their sleep due to this, the research indicates that a calorie deficit helps on average. That does not mean it will help in all cases. It is individual. But on average it helps.
Even in research on non-obese participants there are often positive outcomes.
It makes sense to avoid an overly large calorie deficit, doing it for too long, or getting excessively lean though.
How Much Does All This Matter?
Some of this stuff matters. The further away you are from optimal, the more it likely matters too.
But outside of the caffeine and alcohol parts, other factors of sleep hygiene likely matter more.
I care about the nutrition stuff because I am a dietitian. When you are holding a hammer, everything you see is a nail. But overall, these things can only help so much.
If you are trying to do EVERYTHING you can to get better sleep, or you see some easy wins, it makes sense to implement some of the stuff mentioned here. But it also makes sense to focus on the basic strategies that often help sleep too that are unrelated to food too.