What’s green, shiny and the only thing that makes Superman too fatigued to do his job? It’s… oh wait, that’s kryptonite. While tryptophan might sound like something out of a comic book, its hero powers are very much of this world. In fact, Earthlings like us need it to survive.

Tryptophan is one of the nine essential amino acids required to create protein in the body, and the sole amino acid behind the production of hormones serotonin, melatonin, and vitamin B3 (aka niacin).

This means tryptophan is an integral ingredient for a number of important bodily functions including mood, cognition, digestion, memory, and sleep.

Below, we list the best foods to get tryptophan from, how it benefits the body, and what you should know before supplementing.

Tryptophan fast facts

  • Tryptophan helps our body create essential hormones and vitamins, meaning it directly benefits multiple bodily functions, especially mood, cognition, sleep, memory, and digestion.
  • Foods high in tryptophan include poultry, seaweed, and beef.
  • Experts don’t generally recommend taking tryptophan supplements since it affects multiple bodily functions.
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You probably get enough tryptophan from your diet

While it’s true that our bodies don’t make tryptophan (we have to get it from either food or supplements) most of us get our daily recommendation — 250 to 425 milligrams (mg) a day — through the food we eat.

If you’re concerned you’re not getting enough tryptophan, talk to a doctor first. Since tryptophan affects a range of different functions in the body, it’s usually not recommended as a supplement.

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Chances are you’ve heard turkey is packed with tryptophan. While this isn’t untrue, there are plenty of other foods that contain similarly hefty doses. To see how turkey compares to other tryptophan-containing foods, see the list below:

If you know anything about tryptophan, it’s that it makes you sleepy.

While the common belief that it’s responsible for your post-Thanksgiving dinner snooze isn’t exactly true (your sleepiness is more likely a result of all those carbs, proteins, and booze), tryptophan is extremely important for good sleep health.

Like we said, tryptophan is a precursor for melatonin and serotonin and both of these hormones play crucial roles in maintaining our sleep cycle, aka telling our bodies when it’s time to sleep and wake up.

In fact, a 3-week long study found that participants who took tryptophan supplements fell asleep faster, slept longer, and woke up less throughout the night.

Sleep issues? Opt for melatonin supplements

If you’re looking for a natural sleep aid, consider melatonin supplements — which target the sleep cycle directly — over tryptophan, which can create undesired affects on other aspects of your body.

While still inconclusive, a 2013 meta analysis including 19 studies found high statistical evidence that taking melatonin supplements can lead to better, longer sleep.

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As a precursor to serotonin, tryptophan plays a super important role in our mood and cognition. Although it isn’t understood exactly how serotonin affects our brains, it’s been linked to an array of mental health conditions, including anxiety, depression, addiction, and schizophrenia.

There isn’t a huge amount of conclusive research exploring the link between mental health and tryptophan. But some smaller studies have found links to the following issues:

  • Panic disorders. One study found that balancing tryptophan levels could protect against episodes of anxiety in those with panic disorders.
  • Social functioning. Another found tryptophan supplements improved the sociability levels of patients with behavioral disorders.
  • Aggression. In a UK study of males with preexisting traits of aggression, those given a mix of amino acids (including tryptophan) were subsequently less angry, hostile, and argumentative.
  • Memory. Dutch researchers discovered that low levels of tryptophan can negatively impact long-term memory capabilities.

5-HTP supplements may help some mental health issues

Before tryptophan makes serotonin, it’s synthesized into a molecule called 5-Hydroxytryptophan (5-HTP). Some believe 5-HTP supplements can treat mental health issues like depression by increasing levels of serotonin.

While studies have shown this may be true, we recommend working with a professional before you start supplementation.

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Like we said earlier, supplementing with tryptophan is tricky and probably isn’t even necessary. We recommend talking with a professional about the specific issue you want to address before jumping into supplementation. They can help you work out the most effective course of action.

And if you’re set on taking them, make sure to buy from reputable, trusted brands that have been verified by a third party.

L-tryptophan vs. D-tryptophan

In your research about tryptophan, you might see mentions of both L-tryptophan and D-tryptophan. L-tryptophan is the type of tryptophan found in food and supplements. In fact, our bodies exclusively use L-amino acids. D-amino acids have different orientations that, although found in nature, aren’t generally usable by our bodies.

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Unless you’re eating five tofu and spinach-stuffed turkeys in one go and washing it down with bottles of milk, the chances of you overloading on tryptophan through food is slim.

However, taking supplements of this amino acid has been known to cause issues. Here are some of the most common side effects to watch out for:

  • heartburn
  • indigestion
  • nausea/vomiting
  • loss of appetite
  • headaches
  • change in sex drive
  • dry mouth

Serious side effects

Serious side effects are rare but can happen. Stop taking immediately if you experience any of the following:

  • unwarranted exhaustion or drowsiness
  • blurred vision
  • lighted-headedness
  • weak muscles
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And if you’re taking SSRIs or medication for depression — many of which affect serotonin in the brain — make sure to speak to your doctor before supplementing with tryptophan.

Lastly, you should avoid taking tryptophan supplements altogether if:

  • you’re pregnant or breastfeeding
  • you have liver or kidney issues

Tryptophan supplements and EMS

In the mid to late 1980s, an outbreak of a rare condition called Eosinophilia-myalgia syndrome (EMS) — which caused 10,000 illnesses and 37 deaths — was linked to a line of tryptophan supplements, leading the FDA to ban all tryptophan-containing products.

In 2005, the FDA overturned their ban after they determined that all of the EMS cases linked back to one manufacturer (which is no longer in circulation).

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As we’ve established, tryptophan is essential in supporting numerous areas of health; and by eating a balanced diet — plenty of fruit and veg, foods high in fiber, protein, dairy (or plant-based alternatives) — you should easily be able to obtain the amount required for good well-being.

As such, it’s unlikely that you’ll need to take specific tryptophan supplements — but if this is an avenue you’d like to explore, it’s important to discuss this with your doctor beforehand and make sure you’re clued up on potential side effects.