Phenylalanine comes in several forms as a supplement:
L-phenylalanine is an essential amino acid. It's also found in protein in the foods we eat.
DL-phenylalanine, which contains both the D- and L-forms
You can get all the L-tryptophan that your body needs by eating a healthy, balanced diet. Supplement doses depend on the health condition you are trying to prevent or treat.
Some people take L-tryptophan supplements to try to help them sleep. But research does not show that L-tryptophan supplements are a good or safe treatment for long-term insomnia.
Low levels of L-tryptophan have been seen in people with depression. Some claim that 1 to 3 grams of L-tryptophan daily may help improve your mood or ward off mental health disorders such as:
There is limited research to back up these claims.
Some women take L-tryptophan supplements to try to ease mood swings due to premenstrual syndrome (PMS), also called premenstrual dysphoric disorder (PMDD). The theory is that these conditions may be linked to a problem with serotonin processing in the body, and that L-tryptophan could help that. However, there is little evidence to show this really works.
Early research in people hints that L-tryptophan supplements may be helpful for:
L-tryptophan is found in meats such as turkey and chicken.
It is also found in:
Pumpkin seeds and sesame seeds
Tree nuts, including peanuts and peanut butter
The amount of L-tryptophan in these foods is small compared to supplements.
What are the risks of taking L-tryptophan?
L-tryptophan has been linked to a dangerous, even deadly condition called eosinophilia-myalgia syndrome (EMS). The FDA recalled tryptophan supplements in 1989 after tens of thousands of people who took them became sick, and some died. EMS causes sudden and severe muscle pain, nerve damage, skin changes, and other debilitating symptoms. Doctors saw a lot fewer people with EMS after the ban. Some research suggests the sickness was due to contaminants that got into the supplements during manufacturing in a factory in Japan.
The supplements have since been re-introduced to the U.S. market.
L-tryptophan can interfere with many different medicines. Do not take L-tryptophan if you are on antidepressants known as selective serotonin reuptake inhibitors (SSRIs) or MAO inhibitors. Doing so may lead to a life-threatening condition called serotonin syndrome. Symptoms of serotonin syndrome are:
Severe muscle spasms
Increased body temperature
L-tryptophan supplements should be used with caution in pregnant women.
You should not take L-tryptophan if you have scarring of the liver (cirrhosis).
Always tell your doctor about any supplements you are taking, including natural ones and those bought without a prescription. That way, your doctor can check on any potential side effects or interactions with any medications.