An essential amino acid the body converts into serotonin and melatonin, the signals behind calm mood and sleep. Its most dependable effect is reducing night-time wakefulness, with a smaller, variable mood lift in those not clinically depressed. Verified product purity is essential, and combining it with antidepressants can trigger dangerous serotonin excess. (Full Review)

Protocol

Sleep Dosing

1–3 g

30–60 min before bed

Mood Dosing

0.5–3 g/day

Often divided into daytime doses

Timing & Food

Evening + carbohydrate

Away from high-protein meals

Time to effect

Sleep Continuity

First night

Reduced night-time wakefulness

Mood

1–2 weeks

With consistent use

Benefits

High: Improved sleep continuity

Medium: Enhanced mood in healthy individuals, adjunctive support in depression

Low: Reduced premenstrual irritability, niacin contribution, reduced quarrelsomeness and greater agreeableness

Speculative: Circadian and healthspan support, appetite and satiety regulation

Contraindications

Monoamine oxidase inhibitors (phenelzine, tranylcypromine, selegiline)

Pregnancy or breastfeeding

Carcinoid syndrome

Significant liver impairment (Child-Pugh Class B or C)

History of eosinophilia-myalgia syndrome

Key Interactions

Serotonergic antidepressants (fluoxetine, sertraline, venlafaxine, other SSRIs and SNRIs)

Other prescription serotonergic drugs (tramadol, triptans, lithium, linezolid)

Over-the-counter serotonergic agents (dextromethorphan cough remedies, St. John's Wort)

Sedatives, sleep aids, and alcohol

Serotonin-raising supplements (5-HTP, SAMe, St. John's Wort) and melatonin

Carbidopa (Parkinson's therapy)

Risk & Side Effects

High: Serotonin syndrome with serotonergic drugs, eosinophilia-myalgia syndrome

Medium: Daytime drowsiness and reduced alertness, gastrointestinal distress

Low: Headache, dry mouth, and blurred vision

Speculative: Neurotoxic kynurenine metabolite shunting, chronic serotonergic effects on heart valves

Monitoring

Marker	Target	Why
Serum 25-hydroxyvitamin D	40–60 ng/mL	Helps regulate serotonin synthesis
Plasma vitamin B6 (pyridoxal-5-phosphate)	30–110 nmol/L	Cofactor for converting tryptophan to serotonin
Ferritin	50–100 ng/mL	Iron is a cofactor for the serotonin-building enzyme
hs-CRP	< 1.0 mg/L	High inflammation shunts tryptophan away from serotonin
Complete blood count with eosinophils	Eosinophils < 500 cells/µL	Historical EMS screen if muscle pain arises

Cadence: Reassess sleep and mood at ~2 weeks and 6–8 weeks; labs every 6–12 months as needed

Qualitative Assessment

Sleep quality and number of night-time awakenings
Ease and speed of falling asleep
Daytime mood, calm, and irritability
Daytime alertness (watching for excess grogginess)

L-Tryptophan for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment