The answer is it depends on your goals. In most cases both, and at different times of the day.
The timing of your meals can have a significant impact on how well you sleep.
In this article, I've compiled research from several different sources that reveal when protein and carbs should be eaten based off natural sleeping patterns in the body - including one practical experiment!
Enter tryptophan.
Tryptophan is the key aminoacid for sleep because it ultimately increases melatonin, the sleep hormone. By the end of this post you will know how to optimize its capacity to get inside the brain.
Tryptophan is part of the nine essential aminoacids. That means that we can’t produce it within our bodies, and we obtain it from our diet.
Food sources of tryptophan are fish, poultry, nuts, cheese, leafy greens sunflower seeds, broccoli, peas. Depletion of tryptophan in the body is tightly related to stress levels.
Research on humans suggests that ingesting tryptophan, as well as carbohydrate will positively impact sleep by reducing alertness and decrease sleep latency, or how long it takes us to fall asleep.
In practical terms, when we understand the mechanism of tryptophan in the brain, we can make better decisions on the best times of the day to consume protein and carbohydrate. This leads to increased melatonin production, which can move the needle in favor of increasing total sleep and better sleep latency.
How it works:
Tryptophan is a precursor to serotonin, a neurotransmitter present in the gut and brain. When tryptophan transposes the blood brain barrier, it goes through various enzymatic processes and is converted into serotonin.
Within the pineal gland in the center of the brain, serotonin’s protein functions are changed, and then a methyl group is added turning it into melatonin.
Melatonin is produced throughout the day and released at night, especially when our eyes stop being exposed to blue light.
In sum, tryptophan that we obtain from our diet is metabolized into melatonin via the serotonin pathway in the brain.
Great! So, we simply increase tryptophan intake from our diet to increase melatonin?
I wish it was that simple.
The trick
Tryptophan doesn’t get into the brain on its own. It needs to hop into a transporter to cross the blood brain barrier. Only then it can be used for serotonin synthesis and melatonin production.
Now we have good news and bad news.
Bad news first: Other aminoacids will beat tryptophan in the competition to get into the brain. The winners are always present in the same complete protein foods along with tryptophan, such as leucine, isoleucine, valine, and phenylalanine and tyrosine.
With the competing aminoacids in the blood, tryptophan can’t get on a transporter or into the brain. This can result in down regulation of melatonin for the night.
Good news: We can store tryptophan in the blood all day via consuming those tryptophan rich foods.
The best part: we have the power to make our blood environment more favorable for tryptophan to cross into the brain.
Two Ways of Helping Tryptophan to Win the Race into the Brain:
Less protein later in the day:
High protein meals increase the plasma ratio of competing aminoacids and decrease the plasma ratio of tryptophan. Also, high protein diet increases serum concentrations of catecholamines which are associated with the sympathetic response and more alertness.
In sum, less concentration of competing aminoacids later in the day creates a more favorable environment for tryptophan to be transported into the brain.
Use insulin is an ally:
Moderate intake of well tolerated whole foods carbohydrates, preferably lower glycemic, will trigger release of insulin. Insulin will re-direct the competing aminoacids into muscle cells and away from the blood brain barrier.
This frees up the transporters so that they can take tryptophan across into the brain. The result is serotonin and melatonin production coming back on point.
10-day experiment:
Consider ending your intake of protein dense foods, such as beef, lamb, organs, and fish by about 4PM.
Eggs are one interesting protein that can be consumed later in the day in small amounts for this experiment. Eggs contain choline, which is key for optimal REM sleep. REM sleep is fundamental for our mental fitness and to keep us sharp in the morning. I will publish more on that soon in an upcoming blog post. Eggs can be combined with the proper dose of carbs in the evening.
Make sure that your carb intake is aligned with your activity level. One option is to have most carbs towards the evening. There is no need to be on a high carb diet. Most importantly is ensure that the carbs are well tolerated, preferably cellular carbs , lower glycemic and not processed.
As always avoid consuming carbohydrate on its own to prevent blood glucose spikes. Its good to have the right amount of protein and fat that fits your goals whenever you consume carbohydrates. Metabolic health is key for good sleep!
Lower glycemic carbohydrates combined with fat and protein are a safer way to optimize blood sugar regulation throughout the day and also during sleep. Some whole food carbohydrate examples are taro, yuca, organic, preferably heirloom, potatoes or sweet potatoes, squashes, and plantains, and for those who tolerate legumes, also lentils.
For those working on blood sugar regulation potatoes may promote a higher blood glucose spike than desired. If you are wearing a CGM (continuous glucose monitor) you can test this and take steps to minimize glycemic variability. Squashes in general have a lower carb density. Here is a helpful list of carbohydrate density and glycemic index by the Linus Pauling Institute
Ensure that your daily protein needs are being met and not compromised throughout the experiment. Especially target your heavier protein intake in the morning and early afternoon. A general range of daily protein intake is anywhere between 0.8 to 1.3 grams of protein per kg of body weigh per day.
Important CAVEAT: If your focus is blood sugar regulation, you may have noticed that protein at night prevents blood glucose from going too low in the evening. Always incorporate what works for you before you embark on experiments.
Most common MISTAKE: —> Not enough protein <— Make sure that if you prioritize having protein in the earlier part of the day, have enough to last for the whole day and night. Follow the standard parameters listed above, or personalized levels set by your health provider.
Final points before we wrap up:
Supplemental tryptophan or 5-HTP can increase serotonin but may not be ideal. It is not optimal on the long-term because it is hard to monitor. More often than not long term 5-HCTP supplementation will cause an imbalance of serotonin and dopamine and other cascading effects.
Too much serotonin could keep the brain awake and alert, just like what happens with some SSRI anti-depressant side effects. The food first approach is overall more sustainable than supplementation when possible.
Before supplementing, it’s good to remember that neuroreceptors and hormones act in unison in the body just like a fine-tuned orchestra.
The interconnectedness of hormones and neuroreceptors are such a sophisticated and highly intelligent network. It is best to ask for health professional help before trying to modulate it with supplements.
Lastly, not everyone needs to go for the experiment above unless they have identified an issue with sleep. Some of my athlete clients are perfectly fine having steaks and high protein dinners, and they still sleep well.
If you are tracking your sleep and see room for improvement though, you may consider helping tryptophan out to make its journey into the brain for optimal melatonin production.
Nutrition science aside: All health experiments can be easy to read, but not so easy when we are doing them!
Many of us have the evening meal as our time to wind down. I get you! Evening is also a time to socialize, and it may turn out to be the biggest meal of the day.
Does that ring a bell? If so, you are not alone.
You can consider inviting a friend to join you and create a buddy system for a health experiment. Or you can think about a professional coach to help you out.
A good coach can offer you deep listening and together with you sort out the mini first steps of getting started. This can bring clarity on the experience you are searching for and help you to find our own authentic motivations. Holding space for questions and any ambivalence is another way to make the process fully yours.
You are welcome to drop questions and comments below.
References
On the stimulation by insulin of tryptophan transport across the blood-brain barrier
https://pubmed.ncbi.nlm.nih.gov/6091659/
The effect of insulin upon the influx of tryptophan into the brain of the rabbit
https://pubmed.ncbi.nlm.nih.gov/7021801/
Possible role of insulin in the transport of tyrosine and tryptophan from blood to brain
https://pubmed.ncbi.nlm.nih.gov/941747/
Do carbohydrates affect food intake via neurotransmitter activity?
https://pubmed.ncbi.nlm.nih.gov/2903717/
Insulin effect on metabolism in skeletal muscles and the role of muscles in regulation of glucose homeostasis
https://pubmed.ncbi.nlm.nih.gov/11769387/
Influence of Tryptophan and Serotonin on Mood and Cognition with a Possible Role of the Gut-Brain Axis
https://pubmed.ncbi.nlm.nih.gov/26805875/
Effects of Antidepressants on Sleep
https://pubmed.ncbi.nlm.nih.gov/28791566/
The behavioral effects of food constituents: strategies used in studies of amino acids, protein, carbohydrate and caffeine.
https://pubmed.ncbi.nlm.nih.gov/2980858/
Tryptophan as an evolutionarily conserved signal to brain serotonin: molecular evidence and psychiatric implications