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$32.50- Our Price:
- $23.41
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- UPC: 021078019855
- # SN1985
Source Naturals® L-Tryptophan 500 mg (120 Capsules)
Unlock Serenity and Sweet Dreams with Source Naturals L-Tryptophan 500mg
Restful, uninterrupted sleep and balanced emotional resilience are foundational to human vitality. Source Naturals® L-Tryptophan 500mg provides pharmaceutical-grade, pure L-tryptophan—an essential amino acid that serves as the critical biological precursor to both serotonin (the "calm and contentment" neurotransmitter) and melatonin (the sleep-wake hormone). Because your body cannot synthesize L-tryptophan internally, it must be obtained through balanced nutrition or targeted supplementation. When daily stress, diet variations, or biological factors deplete systemic tryptophan stores, supplementation helps re-establish neurotransmitter balance to encourage faster sleep onset, deeper non-REM sleep architecture, and a stabilized daytime mood.The Science of L-Tryptophan: Mechanism of Action & Neurotransmitter Synthesis
To understand why Source Naturals L-Tryptophan 500mg is so effective, it is essential to trace its biological pathway across the blood-brain barrier (BBB) and into the central nervous system (CNS).The Science of L-Tryptophan: Mechanism of Action & Neurotransmitter Synthesis
To understand why Source Naturals L-Tryptophan 500mg is so effective, it is essential to trace its biological pathway across the blood-brain barrier (BBB) and into the central nervous system (CNS).L-Tryptophan (Diet / Supplement)
¦
? [Transported across BBB via LAT1 Carrier]
L-Tryptophan in Brain
¦
? [Tryptophan Hydroxylase (TPH) — Rate-Limiting Step]
5-Hydroxytryptophan (5-HTP)
¦
? [Aromatic L-Amino Acid Decarboxylase (AADC) + Vitamin B6]
Serotonin (5-HT) --? Supports emotional stability, calm, & satiety
¦
? [Pineal Gland (Enzymatic N-acetylation & methylation in darkness)]
Melatonin --? Governs circadian rhythm & sleep architecture
1. Competitive Blood-Brain Barrier (BBB) Transport
In circulation, L-tryptophan competes directly with other Large Neutral Amino Acids (LNAAs)—such as leucine, isoleucine, valine (BCAAs), tyrosine, and phenylalanine—for access to the shared LAT1 transporter into the brain.- The Carbohydrate/Fruit Juice Connection: Taking L-tryptophan with a small amount of carbohydrate or fruit juice (as recommended on the label) causes a mild insulin release. Insulin directs competing BCAAs into skeletal muscle tissue, clearing the highway and allowing L-tryptophan to cross the blood-brain barrier with maximum efficiency.
2. Enzymatic Rate Limiting (A Built-In Safety Buffer)
Once in the brain, L-tryptophan is converted into 5-HTP by the enzyme tryptophan hydroxylase (TPH). Because TPH is a rate-limiting enzyme, your brain naturally regulates how quickly L-tryptophan converts into serotonin. This metabolic checkpoint prevents sudden, uncontrolled spikes in central serotonin levels, offering a gentle, sustainable, and biologically harmonized pathway compared to direct neurotransmitter stimulation.3. The Niacin & Kynurenine Pathway
Beyond neurotransmitter synthesis, systemic L-tryptophan acts as a precursor for the de novo synthesis of nicotinamide adenine dinucleotide (NAD+/NADH) via the kynurenine pathway. Each 3-capsule serving provides the equivalent of 25 mg of Niacin, supporting cellular energy production, DNA repair, and nervous system health.Primary Benefits of Source Naturals L-Tryptophan 500mg
Natural Sleep Latency and Circadian Support
Clinical trials published in sleep research literature demonstrate that L-tryptophan supplementation significantly reduces sleep onset latency (the time it takes to fall asleep) without disrupting REM or slow-wave deep sleep cycles. Unlike conventional pharmacological sleep aids, L-tryptophan does not cause daytime grogginess or motor-skill suppression when taken at recommended dosages.Mood Stabilization & Emotional Balance
Serotonin produced in the raphe nuclei of the brain stem regulates stress adaptation, patience, and positive affect. By replenishing depleted tryptophan pools, this supplement supports resilience against everyday environmental stressors, mild irritability, and nervous tension.Healthy Appetite Regulation & Craving Control
Brain serotonin signaling directly communicates with the hypothalamus to signal satiety, particularly regarding simple carbohydrates and stress-induced emotional eating.Comparison: L-Tryptophan vs. 5-HTP
| Feature / Metric | L-Tryptophan (Source Naturals 500mg) | 5-HTP (5-Hydroxytryptophan) |
| Metabolic Position | Essential amino acid (Parent precursor) | Intermediate metabolite (1 step closer to serotonin) |
| Rate-Limiting Control | Yes (Regulated by TPH enzyme to prevent sudden surges) | No (Directly bypasses TPH; rapidly converted to serotonin) |
| Site of Conversion | Crosses BBB; selectively synthesized within neurons | Converted in both CNS and peripheral tissues (gastrointestinal tract) |
| Side Effect Profile | Very low incidence of gastrointestinal upset | Higher incidence of nausea, cramping, and loose stools |
| Secondary Pathways | Synthesizes NAD+ / Niacin and supports immune kynurenines | Restricted almost exclusively to serotonin/melatonin pathways |
| Best For | Sustained, steady mood stability and night-long sleep architecture | Short-term, acute serotonin replenishment |
Complete Supplement Facts & Ingredient Breakdown
Source Naturals manufactures under strict cGMP (Current Good Manufacturing Practices) standards. Every batch is identity-verified and lab-tested to ensure the highest chemical purity and absence of contaminants.Supplement Facts
- Serving Size: 3 Capsules
- Servings Per Container: 40
- Capsules Per Bottle: 120 Capsules
- Product Code / SKU: SN1985
- UPC: 021078019855
| Active Ingredient | Amount Per 3 Capsules | Amount Per 1 Capsule | % Daily Value |
| L-Tryptophan (yielding 25 mg Niacin equivalents) | 1.5 g (1,500 mg) | 500 mg | ** |
Other Ingredients
- Gelatin (capsule shell)
- Magnesium Stearate (vegetable-derived flow agent)
- Silica (anti-caking mineral)
- Microcrystalline Cellulose (plant-based plant fiber binder)
- Dibasic Calcium Phosphate (mineral carrier)
Allergen & Purity Declarations
- FREE FROM: Yeast, dairy, egg, gluten, soy, and wheat.
- FREE FROM: Preservatives, artificial colors, artificial flavors, and added fragrances.
- Non-GMO: Formulated with verified premium raw ingredients.
Suggested Use & Dosage Guidelines
- For General Mood & Stress Support (Daytime): Take 1 capsule, three times daily, between meals. For optimal absorption across the blood-brain barrier, consume with a small serving of fruit juice, water, or a complex carbohydrate source, and away from heavy protein meals.
- For Restful Sleep & Circadian Rhythm Support (Bedtime): Take up to 3 capsules (1,500 mg) approximately 30 to 60 minutes before bedtime with water or juice.
- Do not exceed 6 capsules within a 24-hour period unless directed by a licensed physician.
Safety Information, Precautions & Medical Warnings (YMYL)
Important Clinical Warning Regarding Serotonergic Medications: Do NOT use L-Tryptophan if you are currently taking prescription Selective Serotonin Reuptake Inhibitors (SSRIs) (such as fluoxetine, sertraline, citalopram), Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) (such as venlafaxine, duloxetine), Monoamine Oxidase Inhibitors (MAOIs), tricyclic antidepressants, or migraine medications (triptans). Combining exogenous serotonergic precursors with these medications may precipitate Serotonin Syndrome (a rare but potentially life-threatening medical condition characterized by rapid heart rate, agitation, hyperthermia, and neuromuscular abnormalities).- Pregnancy and Lactation: If you are pregnant, planning to become pregnant, or breastfeeding, do not use this product without consulting your OB/GYN or primary healthcare provider.
- Drowsiness Warning: May cause drowsiness. Do not drive a motor vehicle or operate heavy machinery immediately following consumption of sleep-support doses.
- Historical Purity Standards: During the late 1980s, an isolated outbreak of Eosinophilia-Myalgia Syndrome (EMS) was linked to an impure, contaminated batch of synthetic tryptophan from a single foreign manufacturer. Today, the FDA, United States Pharmacopeia (USP), and Source Naturals require stringent microbiological fermentation standards, chromatographic purity testing, and analytical batch validation to ensure 100% safety and purity.
- Storage Instructions: Keep bottle tightly closed. Store in a cool, dry place away from direct sunlight, excess heat, and moisture. Keep out of reach of children. Do not use if the inner safety seal or outer tamper-evident wrap is broken or missing.
Frequently Asked Questions (FAQ)
What makes Source Naturals L-Tryptophan 500mg superior to standalone melatonin?
Melatonin is an end-stage hormone that directs your body when to sleep, but it does not participate in mood regulation or neurotransmitter replenishment. L-Tryptophan is an upstream precursor that allows your brain to synthesize both daytime serotonin and nighttime melatonin on demand, honoring your body's natural circadian rhythm without causing receptor desensitization or morning grogginess.Why should I take L-Tryptophan with fruit juice or carbohydrates?
L-Tryptophan competes with other Large Neutral Amino Acids (BCAAs like leucine, valine, and isoleucine) to cross the blood-brain barrier via the LAT1 transporter. Taking L-tryptophan with fruit juice triggers a small insulin response that draws competing amino acids into muscle tissue, giving L-tryptophan an open pathway into the brain for optimal conversion into serotonin.How quickly does Source Naturals L-Tryptophan take effect?
When taken for sleep support on an empty stomach, peak plasma amino acid levels generally occur within 45 to 90 minutes. For daytime emotional wellness and mood stability, noticeable equilibrium is typically experienced after 5 to 7 days of consistent, divided daily dosing.Can I take Source Naturals L-Tryptophan if I am on an antidepressant?
No. You should not combine L-Tryptophan with SSRIs, SNRIs, MAOIs, or other serotonergic medications without direct medical supervision. The co-administration of serotonin precursors alongside reuptake inhibitors can trigger excessive central serotonin accumulation, increasing the risk of Serotonin Toxicity (Serotonin Syndrome).Is Source Naturals L-Tryptophan tested for purity and EMS contaminants?
Yes. Source Naturals subjects every raw material lot to rigorous quality control procedures, including High-Performance Liquid Chromatography (HPLC) and microbial screening. All products conform to strict FDA cGMP regulations and are free from harmful contaminants.What is the difference between 500mg capsules and taking a single 1500mg tablet?
The 500mg capsule format (SKU: SN1985) offers precise dosing flexibility. It allows users to take a low dose (500mg) during the day for stress modulation, or scale up to 1,000mg - 1,500mg before bed for targeted sleep support, rather than being locked into a fixed, high-dose serving.
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