Tryptophan, melatonin synthesis and sleepiness

I am thinking about purchasing Huel at some point in the near future but as you can imagine I have had a number of queries that I have needed clearing up. My latest query is this: is the amount of the amino acid tryptophan too high at 638% daily?

The reason I ask this is because every time I drink a protein shake I feel really lethargic afterwards, so I Googled it and one suggestion was that the high levels of tryptophan in protein powder (0.4g per scoop in the powder I’m currently using) cause an increase in melatonin biosynthesis, which results in your body “anticipating the onset of darkness” and thinking it’s time to go to sleep.

Could Julian or James reassure me that this is not an actual problem and, and if it isn’t, can they perhaps suggest why I might feel lethargic after drinking a protein shake?

Thanks very much


The tryptophan (trp) is from the natural protein sources. Trp is an essential amino acid so it has a minimum level required to prevent deficiency. However, most people who eat a varied diet of animal and vegetable products will be consuming trp levels similar / higher than from a 2000kcal Huel diet. The proteins in Huel (like most other proteins) are a complex structure of amino acids interlinked and crosslinked into a quaternary structure. This means that in order to free the amino acids, a degree of digestion needs to occur and trp is no exception. So, although Huel is high in trp, it will more of a gradual increase in blood trp levels. Plus the trp has to then cross the blood-brain barrier before it’s involved in melatonin synthesis which happens more slowly. Therefore any lethargy is unlikely to be from trp.

Whey protein is different - it’s naturally short chain protein chains that can be easily hydrolysed into free amino acids, which is why it’s so popular with bodybuilders. Therefore all levels of amino acids, including trp, will rise a lot quicker.

Saying that, I’m not sure why you’re feeling really lethargic. If there was an issue, it’s likely to be only a very small one and I know 1000s of people who consume large amounts of protein powders with no issues, myself included. There might be other factors coming into play:
When do you consume protein drinks?
How much do you consume?
What do you mix it with?
What’s your job?
What sort of exercise do you do?
What’s your solid meal structure?

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If it helps, when I had a full meal with little water, 3 and a bit scoops, 500ml water ( 1:4 ratio) I felt sluggish after, but after an hour the longer term energy kicked in. When I mix more to 1:5, the sluggishness stops and its pure energy.

Since being on Huel I’ve had more energy, motivation and get-up-and-go than I’ve ever had in my life. It’s no secret I’ve never had a good diet, so it’s more that I’m now getting everything I need than some magick potion in Huel, but to have everything in a simple, quick and easy place, means no reason to skip meals, no need to count anything or fuss around with anything. Simply measure water, scoop in and shake. And it tastes great to boot. What’s not to love!