Isotonix® L-Tryptophan

Isotonix® L-Tryptophan

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Single Bottle (30 Servings)

Product Information

  • Promotes mental clarity and understanding of everyday situations
  • May help support healthy perceptions and reactions in daily and stressful situations
  • Helps enhance and stabilize mood
  • May help promote calmness and relaxation
  • Helps promote healthy control of feelings and perceptions
  • Helps maintain healthy levels of serotonin
  • May help enhance mental focus and memory
  • May help support a normal sleep cycle
  • Promotes sleep

Product Information

Isotonix® L-Tryptophan

For anyone who want to promote calmness, relaxation or sleep, or simply wants to enhance their mood, Isotonix L-Tryptophan may be the answer. Unlike prescription mood stabilizers used to treat specific conditions, Isotonix L-Tryptophan is a safe serotonin supplement containing the essential amino acid, l-tryptophan.

Tryptophan has been shown in studies to help maintain normal levels of serotonin, one of the key brain chemicals involved in regulating mood and melatonin. The body cannot naturally produce tryptophan, an amino acid; therefore, it must be a part of the diet or ingested through supplementation.

Helping maintain healthy levels of serotonin in the brain help regulate mood. Unlike most other mood-enhancing supplements and mood stabilizers on the market, Isotonix L-Tryptophan provides maximum results by including members of the B vitamin family that promote the normal absorption of L-tryptophan. Our Isotonix serotonin supplement helps your body maintain healthy levels of serotonin to enhance mood and support sleep.

Bring out the happier you with Isotonix L-Tryptophan.

*These statements have not been evaluated by the Food and Drug Administration. This product(s) is not intended to diagnose, treat, cure or prevent any disease.

For anyone who has experienced stress, difficulty sleeping, or simply wants to enhance their mood, Isotonix L-Tryptophan is the answer. Not to be confused with the culprit of after-thanksgiving dinner lethargy, Isotonix L-Tryptophan is an isotonic capable form of the essential amino acid, l-tryptophan. Unlike other leading brands, Isotonix L-Tryptophan provides maximum results by including niacin and Vitamin B6, members of the B vitamin family, which are key players in the absorption of l-tryptophan. By supplementing with Isotonix L-tryptophan, healthy levels of serotonin in the brain will help enhance mood and support restful sleep leading to a healthier and happier you.

SHOP.COM Reviews

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Works great to help me fall asleep.

by DebraG


I have found that taking this product 30 minutes before retiring, has helped me to fall asleep fast and to rest much longer at night.

Sleep Help

by ThereseW

Shop Consultant


I have had sleep issues in the past. This is my go to if I get in bed and my eyes aren't closing. If I know I am having sleep issues due to stress or a very early meeting, then I take the Tryptophan about 2 hours before bedtime. It works!

Great Purchase - Amazing Product


Shop Consultant


This product is amazing & that is an understatement. I have never taken a sleep aid before but I one day decided to order another Market America product called “Bliss” and loved it. I used it primarily as a sleep aid because it relaxed me so much. Recently, I discovered that I could not order Bliss separately but had to instead get it in a “packaged deal” so I hesitantly decided to try and eventually ordered the Isotonix L-Tryptophan instead. When I first took the L-Tryptophan, I used one capful and within 30-minutes I started feeling very relaxed and fell asleep. When I read the bottle and discovered that I could take 1-2 capfuls, I took 2 capfuls and that was even better! It make me more relaxed and sleepy faster. My rest was extremely peaceful and I woke up feeling refreshed. I definitely prefer the L-Tryptophan over Bliss although both products are great, I would say that the L-Tryptophan is amazing. I wish they made a larger bottle as I find myself limiting my dosage to 1 capful instead of the normal 2!

by DavidR


I've long had difficulty relaxing fully and completely enough to fall asleep naturally at bedtime. However, since I've started taking Isotonix L-Tryptoaphan about a half hour before bedtime I find that it helps put me into a relaxed and rather drowsy state which makes it much easier for me to fall asleep. I would recomment this product to anyone who has trouble falling asleep - it really works and it's a much more natural and healthy solution vs. taking sleep meds.

This actually works!!

by DavidR


I've struggled with sleep issues for many years, specifically falling asleep. After taking this product the past three nights, I can honestly say this product works. I've taken it as directed on the bottle and within a few minutes I am beginning to feel drowsy and ready for sleep. I am impressed and very happy with it.


 L-Tryptophan (500 mg)
An essential amino acid that promotes the normal synthesis and structure of proteins. In the body, L-tryptophan is converted into niacin (vitamin B3) and serotonin, a neurotransmitter which promotes the body’s ability to regulate anger, aggression, mood, and sleep. By supplementing with Isotonix L-Tryptophan, serotonin production can be supported, which will promote sleep and enhance mood.*


The metabolism of L-tryptophan to serotonin is supported in large part by the following vitamins:  


Vitamin C (75 mg)
A water-soluble vitamin which acts as an antioxidant, supports normal growth and repair of body tissues, supports cardiovascular health, protects against free radicals, and supports cognitive health and performance. Vitamin C supports the hydroxylation of L-tryptophan to serotonin.*


Niacin (Vitamin B3) (20 mg)

Plays an essential role as a coenzyme (NAPH/ NADPH) for about 200 enzymes which promote normal tissue respiration, synthesis of fatty acids and steroid hormones, the metabolism of carbohydrates and amino acids, and the transport of hydrogen. When niacin levels are low, the body can use L-tryptophan to manufacture the vitamin. To produce 1 mg of niacin, the body must use 60 mg of L-tryptophan, a process which can rapidly deplete L-tryptophan levels. When niacin levels are sufficient, L-tryptophan can be used for other needs such as retaining healthy levels of serotonin.*  


Pyridoxine HCl (Vitamin B6) (4 mg)

Promotes the normal conduction of nerve impulses, regulation of steroid hormones, catabolism of glycogen for glucose, heme synthesis, and the synthesis/metabolism of amino acids and neurotransmitters. After conversion to pyridoxal phosphate (PLP), vitamin B6 acts as a cofactor for many enzymatic reactions involving L-tryptophan, including L-tryptophan’s conversion to serotonin.* 


  • Bell, C., et al. Tryptophan depletion and its implications for psychiatry. British Journal of Psychiatry. 178: 399-405, 2001.
  • Booij, L., et al. Acute tryptophan depletion as a model of depressive relapse. British Journal of Psychiatry. 187: 148-154, 2005.
  • Monograph. L-Tryptophan. Alternative Medicine Review. 11(1): 52-56, 2006.
    Murphy, S., et al. Tryptophan supplementation induces a positive bias in the processing of emotional material in healthy female volunteers.
  • Psychopharmacology (Berlin). 187(1): 121-130, 2006.
  • Neumeister, A., et al. Effects of tryptophan depletion vs catecholamine depletion in patients with seasonal affective disorder in remission with light therapy. Archives of General Psychiatry. 55: 524-530, 1998.
  • aan het Rot, M., et al. Social behaviour and mood in everyday life: the effects of tryptophan in quarrelsome individuals. Journal of Psychiatry and Neuroscience. 31(4): 253-262, 2006.
  • Russo, S, et al. Tryptophan as a link between psychopathology and somatic states. Psychosomatic Medicine. 65: 665-671, 2003.
  • South, J. L-Tryptophan, nature’s answer to Prozac®. International Antiaging Systems (IAS) Bulletin, 2007. 
  • van der Veen, F., et al. Effects of acute tryptophan depletion on mood and facial emotion perception related brain activation and performance in healthy women with and without a family history of depression. Neuropsychopharmacology. 32: 216-224, 2007.
  • Voderholzer, U., et al. Impact of experimentally induced serotonin deficiency by tryptophan depletion on sleep EEG in healthy subjects. Neuropsychopharmacology 18(2): 112-124, 1998.
  • Cools, R., et al. Tryptophan depletion disrupts the motivational guidance of goal-directed behavior as a function of trait impulsivity. Neuropsychopharmacology. 30:1362-1373, 2005.
  • Del-Ben, C., et al. Serotonergic modulation of face-emotion recognition. Brazilian Journal of Medical and Biological Research. 41(4): 263-269, 2008.
  • LeMarquand, D., et al. Behavioral disinhibition induced by tryptophan depletion in nonalcoholic young men with multigenerational family histories of paternal alcoholism. American Journal of Psychiatry. 156: 1771-1779, 1999.
  • Murphy, S., et al. Tryptophan supplementation induces a positive bias in the processing of emotional material in healthy female volunteers. Psychopharmacology (Berlin). 187(1): 121-130, 2006.
  • Rubinsztein, J., et al. Acute dietary tryptophan depletion impairs maintenance of “affective set” and delayed visual recognition in healthy volunteers. Psychopharmacology. 154: 319-326, 2001.
  • Griffiths, W., et al. Tryptophan and sleep in young adults. Psychophysiology. 9(3): 345-356, 1972.
  • Hartmann, E.. and Spinweber, C. Sleep induced by L-tryptophan. Effect of dosages within the normal dietary intake. The Journal of Nervous and Mental Disease. 167(8): 497-499, 1979.
  • Steritei, R. How to get a good night’s sleep with tryptophan. NaturDoctor. 2007. 


How do I take Isotonix L-Tryptophan?
For sleep support, take 30 minutes prior to bedtime. Pour 1-2 level, white bottle capfuls of powder into the overcap. Add water to the line on the overcap (60mL/2 fl. oz for 1 capful; 120mL/4 fl. oz. for two capfuls), stir and drink. 

For mood enhancement, pour one level, white bottle capful of powder into the overcap. Add water to the line on the overcap (60 ml/2 fl. oz for 1 capful), stir and drink.

Are there any warnings associated with taking Isotonix L-Tryptophan?
If you are currently taking monoamine oxidase inhibitors (MAOI) or other antidepressants, such as Zoloft or Paxil, psychoactive or tranquilizing drugs, such as Clonopin or Valium, or pain medications, such as Demerol or Ultram, you should consult your physician before using this product. If you are taking any other prescription drugs or have an ongoing medical condition, you should consult your physician before using this product. Take this supplement separately from prescription medications. Women who are pregnant or breastfeeding should not use this product. Do not drive or operate heavy machinery until you know how this product can affect you, as drowsiness may occur.

How will Isotonix L-Tryptophan affect sleeping?
Isotonix L-Tryptophan can promote sleep and support a normal sleep cycle.*

Why is Isotonix L-Tryptophan important?
Tryptophan is an essential amino acid that is the precursor for serotonin (a neurotransmitter). It can help to enhance and stabilize mood, help to promote calmness and relaxation, and may help to enhance mental focus and memory.*

What are some food sources rich in the amino acid Tryptophan besides dairy products and turkey?
Foods that are considered sources of tryptophan are dairy products, beef, poultry, barley, brown rice, fish, soybeans and peanuts.

Are there any allergens associated with Isotonix L-Tryptophan?
There are no known allergens associated with Isotonix L-Tryptophan. It is suitable for vegetarians.

What is the difference between 5-HTP and Isotonix L-Tryptophan?
5-HTP stands for 5-Hydroxytryptophan. 5-HTP is a supplement that is converted in the brain to serotonin. Tryptophan is an amino acid that converts into 5-Hydroxytryptophan which then converts into serotonin. L-Tryptophan is the basic building block of serotonin, and 5-HTP is a synthesized intermediate compound closer to serotonin. 

When should I start to see/feel the effects Isotonix L-Tryptophan? What should I expect?
The benefits of Isotonix L-Tryptophan should be noticeable within a day of the first serving. Please remember that everyone’s body is different, so for some it may take more or less time to notice the benefits of Isotonix L-Tryptophan. The isotonic state of the suspension allows nutrients to pass directly into the small intestine and rapidly absorb into the bloodstream.*

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