Sleep Like It’s Thanksgiving Dinner: Reviewing L-Tryptophan by Source Naturals

It happens every Thanksgiving: I stuff my face, and just as I’m getting settled in on the couch for some football, the drowsiness sets in — all I want is a nap. Most people blame the tryptophan in the turkey, a known sleep-inducing amino acid, but while the tryptophan does play a part in the post-meal sleepiness, the bigger culprit is the carbs.

An essential amino acid — meaning that the body needs it to function but does not produce it — tryptophan or L-tryptophan is found in a variety of foods. In fact, cheese, red meat, lentils, soy, and eggs all have a larger concentration of tryptophan than turkey.

Stated Use

Helps Support Relaxation, Restful Sleep, and Positive Mood

Active Ingredients

Source Naturals L-Tryptophan LabelA colleague recommended the L-Tryptophan when I was having trouble falling asleep while working on a stressful project. I chose the Source Naturals brand for its Non-GMO validation, and the fact that it is hypoallergenic, containing no gluten, yeast, eggs, dairy, soy, sugar, starch, artificial colors, flavors, or fragrances.

  • L-Tryptophan — This amino acid plays a part in the synthesis of both melatonin and serotonin hormones involved with mood and stress response and sleep/wake cycles.
  • Iron — A naturally occurring mineral in tryptophan, iron is responsible for a number of functions in the body and helps prevent anemia.

In addition to the above main ingredients, this supplement contains magnesium stearate and calcium phosphate, both known to aid sleep.

My Experience

I followed the instructions on the bottle and took 3 capsules before bed. I usually have trouble shutting off my brain when my head hits the pillow, and I feel like the L-Tryptophan helped me relax and fall asleep quicker than I normally would. I did wake up a couple of times during the night, but fell right back asleep and woke up 8 hours later, feeling well-rested and alert.


  • Very gentle
  • No grogginess or fogginess in the morning
  • Helped me shut off my brain


  • Three pills can become a lot, if you are taking them nightly.

The Final Word

Natural and gentle, Source Naturals L-Tryptophan will definitely stay in my sleep supplement rotation. The bottle also suggests taking 1 capsule three times daily between meals as a mood enhancer. I have not tried that yet, but will report back when I do. I will also experiment stacking the L-Tryptophan with another single-ingredient supplement, like melatonin, for a more uninterrupted sleep.


Having written hundreds of articles on, Caitlyn knows what she's talking about when it comes to getting the best night's sleep. When not sleeping, reading about sleep, or writing about sleep, you can usually find her at the gym. Want to get in touch? The best way is to leave a comment on one of her articles.