Side effects of L-tryptophan may include:

When tryptophan is plentiful, two tryptophan molecules bind the repressor protein at the operator sequence. This physically blocks the RNA polymerase from transcribing the tryptophan genes. When tryptophan is absent, the repressor protein does not bind to the operator and the genes are transcribed.

The body uses tryptophan to help make melatonin and serotonin. Melatonin helps regulate the sleep-wake cycle, and serotonin is thought to help regulate appetite, sleep, mood, and pain. The liver can also use tryptophan to produce niacin (vitamin B3), which is needed for energy metabolism and DNA production.

• Blurred vision.
• Dizziness.
• Drowsiness and fatigue.
• Head twitching.
• Hives.
• Nausea.
• Loss of muscle coordination and muscle stiffness.
• Strong, pounding heart beat (palpitations)

Foods known to be high in tryptophan include:

• chicken.
• eggs.
• cheese.
• fish.
• peanuts.
• pumpkin and sesame seeds.
• milk.
• turkey.

L-tryptophan is only available from doctors. It should be taken several hours before or after meals. Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder.

Since tryptophan is an amino acid found in many foods, it is assumed to be safe in normal quantities. It’s estimated that a typical diet contains 1 gram per day, but some individuals choose to supplement with doses of up to 5 grams per day ( 29 ).

Tryptophan, at a dose of 1 gram taken 45 minutes before bedtime, will decrease the time taken to fall asleep in those with mild insomnia and in those with a long sleep latency. At this dose, it has no effect on sleep architecture, and no effects on alertness the next day have been detected.

Supplementation with tryptophan has been shown in numerous clinical trials to be safe, well-tolerated, and supportive of well-being, calmness, relaxation, sleep, and appetite control. For best results, take tryptophan on an empty stomach, or with a small serving of carbohydrates.

When you consume L-tryptophan, your body absorbs it and changes it to eventually become a hormone called serotonin. Serotonin transmits signals between your nerve cells and also narrows (constricts) blood vessels. The amount of serotonin in the brain can affect mood.

Adults: Take 8 to 12 grams of L-tryptophan by mouth per day. L-tryptophan should be taken in divided doses of three or four times a day.

Taking L-tryptophan might decrease the amount of time it takes to fall asleep and improve mood in healthy people with sleep problems. Taking L-tryptophan might also improve sleep in people with sleep problems related to withdrawal of illegal drugs.

L-tryptophan is safe when a person consumes it as part of their regular diet. When consuming it in supplement form, a person may experience minor side effects. According to one study , some common but mild side effects include: nausea.

5-HTP is generally recommended over l-tryptophan because it crosses the blood-brain barrier at a higher rate, is converted into serotonin more efficiently than l-tryptophan, and has a more pronounced antidepressant effect.

In a double-blind study, 58 percent of generally anxious patients (79 total subjects) randomized to L-tryptophan 3 grams per day reported significantly greater reduction in baseline anxiety compared to individuals who received a placebo.

While typical intake for many individuals is approximately 900 to 1000 mg daily, the recommended daily allowance for adults is estimated to be between 250 mg/day5,12,13 and 425 mg/day,4,14,15 which translates to a dietary intake of 3.5 to 6.0 mg/kg of body weight per day.

In humans, the administration of tryptophan to normotensive human subjects causes a slight increase in blood pressure (28) and a small decline in stressed (29) and hypertensive (30) subjects.

By increasing serotonin levels, tryptophan can function as an appetite suppressant at low doses, and is sometimes very effective for weight loss. As well, tryptophan has been successfully used as a sleep aid.

Tryptophan can be found in the following foods:

• Milk. Whole Milk is one of the largest sources of tryptophan, including 732 milligrams per quart.
• Canned Tuna. Canned tuna is another good source of tryptophan, including 472 milligrams per ounce.
• Turkey and Chicken.
• Oats.
• Cheese.
• Nuts and Seeds.

Tryptophan (l‐tryptophan) is a precursor of serotonin [5‐hydroxytryptamine (5‐HT)], while phenylalanine and tyrosine are precursors of the catecholamine neurotransmitters dopamine, norepinephrine and epinephrine.

Adults who take tryptophan supplements take doses of 5 grams before bed to help improve sleep. By comparison, two servings of turkey contain about 410 milligrams of tryptophan — close to the daily requirement of this important nutrient.

No matter what type of poultry you like to eat, you’ll get 250 to 310 milligrams of tryptophan in a 3-ounce serving. Turkey has a little less than chicken, and dark meat contains less than light meat. Dark-meat turkey has 250 milligrams compared to dark-meat chicken with 270 milligrams of tryptophan.

Tryptophan is an amino acid that is a precursor for the brain chemical serotonin, which is associated with healthy sleep. But there is no more tryptophan in turkey than in other common meats like chicken and beef. Other foods, including nuts and cheeses, contain more.

Peanut butter is loaded with tryptophan, but also has been known to boost your metabolism, so you can burn more calories while you sleep and through the next morning. For an added benefit, put the peanut butter on half of a whole-wheat bagel to get those sleep-inducing carbs.

Nuts. Nuts are a great source of protein, including the amino acid tryptophan. The nuts with the most tryptophan are cashews, pistachios, and almonds. Include these in your Thanksgiving stuffing and you’ll have as much — or more — tryptophan than if you’d eaten turkey.