Turkey is probably the most celebrated source of tryptophan, the amino acid thought to contribute to drowsiness after a big Thanksgiving meal. Tryptophan is found naturally in many foods (aside from turkey, it is found in other meats, as well as nuts and seeds, milk, and some fruits and vegetables), and is also available in supplements. 5-HTP is a derivative of tryptophan, and is found in foods in small but not significant amounts, and it is available in supplement form.
In a chemical chain reaction in the body, tryptophan is converted into 5-HTP, which is then converted into serotonin. In other words, tryptophan and 5-HTP both act as precursors to the production of serotonin in the brain. Serotonin is an important hormone and neurotransmitter, low levels of which have been linked to depression and mood disorders, even insomnia. Take a look:
1. Depression. Some of the human research on tryptophan has been done via short-term tryptophan-deficient diets, which show that a lack of tryptophan quickly leads to feelings of depression. Women may be more susceptible than men to low tryptophan levels, and people with a history of depression are particularly sensitive. Studies have found that tryptophan supplements work as well as many antidepressant drugs. The beneficial effect of tryptophan on depression may be related to its ability to boost several neurotransmitters, including serotonin and dopamine (linked to pleasurable feelings).
Seasonal Affective Disorder (SAD) is thought to be a result of fewer hours of sunlight during the fall and winter. Studies have found that combining tryptophan supplements with a full-spectrum light box (mimicking morning exposure to sunlight) leads to improvements in people with SAD.
2. Sleep. Serotonin serves as a precursor to melatonin, a neurohormone that regulates the body’s sleep cycle. Tryptophan has been found to help in sleep disorders, and it has the advantage of not causing morning grogginess. Some researchers have also reported that tryptophan supplements lead to improvements in sleep apnea. In one study, people who took 5-HTP went to sleep quicker and slept more deeply than those who took a placebo. These researchers recommend 200-400 mg at night for 6-12 weeks to stimulate serotonin.
3. Thinking and Behavior. Tryptophan may benefit cognition and mitigate aggressive behavior. A lack of tryptophan interferes with normal thinking processes, including learning, memory, recall, and mental flexibility. Conversely, maintaining an adequate intake of tryptophan (e.g., from protein) may help preserve cognitive function. Both animal and human studies have found that serotonin inhibits aggressive behavior. In human research, tryptophan depletion increases aggressive behavior, especially in people who have a history of aggressiveness.
There are some considerations to keep in mind before you take either tryptophan (a.k.a. L-tryptophan) or 5-HTP. First, effectiveness is influenced by other dietary proteins. Therefore, take tryptophan or 5-HTP on an empty stomach at least 15 minutes before—or two hours after—eating.
Second, the recommended dosage for tryptophan is about 10 times higher than it is for 5-HTP. For sleep disorders, try 1 gm (1,000 mg) of tryptophan or 100 mg of 5-HTP before bed. For depression, try either 500 mg of tryptophan or 50 mg of 5-HTP three times daily, and take the last dose just before bed.