Source Naturals L-Arginine and L-Citrulline Complex (1000 mg, 120 Tablets)
A high-potency, dual-amino acid formula engineered to elevate nitric oxide production, support vascular elasticity, and accelerate physical recovery. By combining two complementary amino acids in an optimal ratio, this complex bypasses the common absorption limits of standalone arginine.
Quick Product Summary & Highlights
✓Potent Synergistic Blend: 750 mg of free-form L-Arginine HCl plus 250 mg of pure L-Citrulline per tablet.
✓Enhanced Bioavailability: L-Citrulline protects L-Arginine from liver breakdown, maintaining elevated blood flow signals for longer periods.
✓Exercise Recovery: Helps clear cellular ammonia waste produced during intense physical workouts.
✓Pure Formulation: Free of yeast, dairy, eggs, gluten, soy, wheat, artificial flavors, and preservatives.
SKU: SN2043Format: 120 TabletsPotency: 1,000 mg Active ComplexManufacturer: Source Naturals
How It Works: The Nitric Oxide "Power Couple" Explained in Plain English
When you exercise or want to support healthy blood pressure, your body relies on a microscopic signaling gas called nitric oxide (NO). Think of nitric oxide as your body's personal traffic controller for your circulatory system. When your blood vessels produce nitric oxide, they relax and widen—a process known as vasodilation. This creates a wider, smoother highway for oxygen, red blood cells, and nutrients to reach your heart, brain, and active muscles.
Why Combining L-Arginine and L-Citrulline Outperforms Either Alone
Many people take plain L-arginine supplements hoping for an immediate surge in blood flow. However, your digestive tract and liver contain an enzyme called arginase. This enzyme acts like a toll booth, neutralizing up to 60% of swallowed L-arginine before it ever reaches your general bloodstream.
That is where L-Citrulline comes to the rescue. L-Citrulline slips past the liver unbothered. Once in your kidneys and bloodstream, it converts directly into L-arginine. Even better, research reveals that L-citrulline actually acts as a shield, slowing down the arginase enzyme so your supplemental L-arginine can survive and do its job. Together, they create a rapid spike and sustained release of circulating nitric oxide.
Supplement Route
Speed of Action
Liver Breakdown Resistance
Blood Arginine Duration
L-Arginine Alone
Fast Initial Spike
Low (Heavy breakdown by arginase)
Short (1 to 2 hours)
L-Citrulline Alone
Delayed Onset
High (Completely bypasses liver)
Prolonged (4 to 6 hours)
Source Naturals Complex (Arginine + Citrulline)
Immediate & Sustained
Optimal (Synergistic enzyme inhibition)
Extended Blood Plasma Plateau
Key Health Benefits: What You Can Expect
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1. Optimal Muscle Pumps & Exercise Stamina
During intense weight lifting or endurance cardio, your muscles burn through fuel and demand immediate oxygen. By promoting vasodilation, this complex helps deliver oxygen-rich blood directly to working muscle fibers, resulting in fuller muscular fullness ("pumps") and reduced perceived exertion during hard sets.
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2. Ammonia Clearance & Faster Recovery
Muscular fatigue is not just about running out of energy; it is also caused by the buildup of toxic metabolic waste products like ammonia. L-Citrulline is an essential component of the urea cycle, helping your liver convert toxic ammonia into harmless urea for excretion, reducing post-workout soreness.
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3. Everyday Vascular & Endothelial Health
The inner lining of your blood vessels is called the endothelium. Healthy endothelial cells keep blood vessels pliable and elastic rather than stiff. Consistent amino acid supplementation supports natural arterial flexibility and promotes healthy blood pressure levels already within the normal range.
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4. Healthy Peripheral Circulation
Do you struggle with cold hands and feet or sluggish circulation when seated for long stretches? By supporting systemic arterial dilation, the L-Arginine and L-Citrulline Complex encourages warm, uninterrupted blood flow out to your extremities and fingertips.
Scientific Backing & Clinical Study Citations
At VitaNet Online, we prioritize evidence-based nutritional science. The effectiveness of pairing L-arginine with L-citrulline is verified in numerous double-blind, peer-reviewed human clinical trials. Below are key medical references validating this specific mechanism:
Study 1: Synergistic Elevation of Plasma L-Arginine and Nitric Oxide
Finding: Researchers found that oral co-administration of L-citrulline and L-arginine immediately and synergistically increased plasma arginine concentrations and nitrite/nitrate (NOx) levels much more effectively than taking either amino acid alone at equal dosages.
Citation: Morita M, Hayashi T, Ochiai M, Maeda M, Yamaguchi T, Ina K, Kuzuya M. (2014). Biochemical and Biophysical Research Communications, 454(2):246-251. DOI: 10.1016/j.bbrc.2014.10.029.
Study 2: Real-World Cycling Performance & Muscle Soreness Reduction
Finding: In a randomized, double-blind, placebo-controlled crossover trial with trained athletes, 7 days of combined L-arginine and L-citrulline significantly improved power output during high-intensity exercise and dramatically reduced subjective post-workout leg soreness.
Citation: Suzuki T, Morita M, Kobayashi Y, Kamimura A. (2019). European Journal of Applied Physiology, 119(5):1075-1084. DOI: 10.1007/s00421-019-04097-w.
Study 3: Pharmacokinetics of Oral L-Citrulline Bypassing Hepatic Clearance
Finding: This clinical trial demonstrated that oral L-citrulline efficiently avoids first-pass splanchnic metabolism in the gut and liver, boosting systemic L-arginine bioavailability and promoting nitric oxide-dependent endothelial vasodilation without gastrointestinal distress.
Citation: Schwedhelm E, Maas R, Freese R, Jung D, Lukacs Z, Jambrecina A, Spickler W, Böger RH. (2008). British Journal of Clinical Pharmacology, 65(1):51-59. DOI: 10.1111/j.1365-2125.2007.02990.x.
Study 4: Systemic Vascular Tone & Blood Pressure Modulation
Finding: Systematic clinical evaluation demonstrated that oral supplementation with arginine and citrulline supports endothelial relaxation, preserves microvascular health, and assists in the regular maintenance of healthy resting blood pressure.
Citation: Khalaf D, Krüger M, Wehland M, Infanger M, Grimm D. (2019). Nutrients, 11(7):1679. DOI: 10.3390/nu11071679.
Source Naturals operates under strict Good Manufacturing Practices (cGMP). Every batch undergoes rigorous identity, purity, and potency testing so you know exactly what is inside every single tablet.
Supplement Facts
Serving Size: 1 Tablet
Servings Per Container: 120
Contains NO yeast, dairy, egg, gluten, soy, or wheat. Free of sugar, starch, salt, preservatives, artificial colors, artificial flavors, and fragrances. Suitable for vegetarians.
How to Take for Best Results: Dosage, Timing & Experience Tips
1Standard Daily Serving
Take 1 tablet four times daily. Spreading the dose throughout the day provides a steady supply of precursors to keep nitric oxide levels elevated from morning to night.
2Pre-Workout Protocol
If using for exercise enhancement or gym sessions, take 1 to 2 tablets approximately 45 to 60 minutes before training with a large glass of water.
3With or Without Food?
Free-form amino acids absorb best on an empty stomach or between meals (at least 30 minutes before food or 2 hours after). If you have a sensitive stomach, taking them with a light snack is completely acceptable.
4Hydration Tip
Nitric oxide production and ammonia clearance require adequate fluids. Drink at least 8 to 12 ounces of water with each tablet to support kidney filtration and blood volume expansion.
Because L-Arginine and L-Citrulline directly influence blood vessel relaxation and systemic circulation, you must observe the following precautions:
Prior Heart Attack Warning: Do not take this supplement if you have recently experienced an acute myocardial infarction (heart attack).
Prescription Nitrates & ED Medications: Do not combine this product with prescription nitroglycerin or phosphodiesterase-5 (PDE-5) inhibitors (such as sildenafil or tadalafil). Combining nitric oxide donors with these medications can trigger a dangerous, life-threatening drop in blood pressure.
Hypotension & Blood Pressure Drugs: If you take prescription blood pressure medication (antihypertensives) or have chronic low blood pressure, consult your physician before use.
Pregnancy & Nursing: If you are pregnant, planning to become pregnant, or breastfeeding, do not use without explicit physician supervision.
Upcoming Surgery: Discontinue taking this supplement at least two weeks prior to scheduled surgery to prevent uncontrolled vascular dilation during anesthesia.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Always speak with your qualified healthcare provider prior to starting any dietary supplement.
Frequently Asked Questions (FAQ)
What is the advantage of taking L-Arginine and L-Citrulline together?
Taking them together solves the "arginine breakdown" problem. L-Arginine provides an immediate source of nitric oxide, while L-Citrulline bypasses the liver and is converted into L-arginine inside the kidneys. In addition, citrulline slows down arginase enzymes, allowing blood levels of arginine to stay elevated for up to twice as long as arginine taken alone.
How long does it take for this complex to start working?
For exercise performance and muscle pumps, most users notice increased blood flow and vasodilation within 45 to 60 minutes after ingestion. For cardiovascular support and resting blood pressure benefits, clinical studies indicate consistent daily use for 1 to 4 weeks delivers the best cumulative results.
Can I take all 4 tablets at the same time?
It is best to space the 4 tablets throughout the day (e.g., morning, lunch, pre-workout, and evening). Spreading the dosage maintains steady nitric oxide concentrations in your bloodstream. However, many athletes choose to take 2 tablets about an hour before training without adverse effects.
Does this supplement cause stomach upset?
High doses of single L-arginine (5 to 10 grams at once) can cause loose stools or cramping. Because this complex combines 750 mg of arginine with 250 mg of gentle citrulline, gastrointestinal side effects are rare. If you experience stomach sensitivity, take your tablet with a small meal.
Will this complex help with cold hands and cold feet?
Yes. Cold extremities are often caused by narrowed peripheral blood vessels. By encouraging smooth muscle relaxation and microvascular dilation, nitric oxide helps warm blood circulate to the fingers and toes.
Is Source Naturals L-Arginine L-Citrulline Complex allergen-free?
Yes. This formula contains no gluten, wheat, soy, dairy, eggs, yeast, sugar, salt, or artificial preservatives, colors, or flavors.
