L-Glutamine + L-Leucine by California Gold Nutrition is a dual-action amino acid supplement designed to support both gastrointestinal and muscular health. L-Glutamine, the primary ingredient by product naming and mechanistic focus, plays a critical role in maintaining gut barrier function, serving as a key fuel source for enterocytes and immune cells. Clinical research shows that glutamine supplementation can reduce intestinal permeability in adults, particularly under stress or catabolic conditions [1], and supports antioxidant defenses via glutathione synthesis [2]. However, benefits are dose-dependent, with therapeutic effects typically observed at 5–10 g/day—far above the 500 mg provided per serving.
L-Leucine, while not named first, complements glutamine by targeting muscle protein synthesis through activation of the mTOR pathway. It acts both as a substrate and signaling molecule, enhancing anabolic responses especially in older adults or those with suboptimal protein intake [3][4]. At 500 mg per serving, however, this formulation delivers only a fraction of the 3–5 g/day typically studied for sarcopenia or muscle support. While safe and bioavailable in free-form, the dose limits its efficacy as a standalone intervention for muscle preservation or gut repair without multiple servings.
Quick Summary
Full transparency: both ingredients are listed with exact amounts per serving, and there are no proprietary blends or hidden fillers.
Efficacy is limited by subclinical dosing of the primary ingredient, L-Glutamine. While the formulation is rational and ingredients are well-chosen, 500 mg is far below the 5–10 g/day typically required for gut barrier benefits. Multiple servings (up to 10) would be needed to approach therapeutic levels.
Both L-Glutamine and L-Leucine are in free-form, highly bioavailable powders with rapid absorption. No enhancers (e.g., piperine) are used, but the forms themselves are well-absorbed, earning a high score with minor deduction for lack of advanced delivery systems.
Excellent safety profile at this dose. Both amino acids are endogenous and well-tolerated. Warnings apply only at high doses or in specific conditions like maple syrup urine disease (leucine) or liver/renal impairment (glutamine).
Suggested: 10 servings/day to reach clinical midpoint
Why Take This Product
Key Benefits
- Supports Gut Barrier Function: L-Glutamine helps maintain intestinal tight junctions and reduces permeability, particularly in adults under physiological stress [1]. It serves as a primary energy source for enterocytes and supports gut-associated lymphoid tissue.
- Enhances Immune Cell Metabolism: As a fuel source for immune cells, glutamine supports immune function during catabolic states such as intense exercise or recovery, though effects are more pronounced at higher doses [2].
- May Aid Recovery from Exercise: Glutamine modulates post-exercise IL-6 levels, suggesting immunomodulatory effects, while leucine supports muscle repair—though both require higher doses for optimal impact [5].
Who Should Take This
Potential Side Effects
Ingredient Breakdown
Each serving delivers 500 mg of L-Glutamine and 500 mg of L-Leucine in free-form, readily absorbable amino acid powders. These forms ensure high bioavailability and rapid plasma uptake, though the doses are significantly below typical clinical ranges.
Primary Ingredients
L-Glutamine
Gut barrier support, immune modulation, antioxidant synthesis
Dose is 10% of the clinical midpoint (7.5 g). Therapeutic effects for gut health typically require 5–10 g/day. Parenteral use is contraindicated in critical illness; enteral use is safe. This low dose may offer mild support but is insufficient for clinical indications.
A conditionally essential amino acid that fuels enterocytes and immune cells, supports tight junction integrity, and enhances glutathione production. Shown to reduce intestinal permeability in adults [1].
Supporting Ingredients
There is 1 supporting ingredient.
Practical Recommendations
- Increase Serving Size For Clinical Effect: To achieve gut barrier benefits, consider taking 10 servings (5 g) of L-Glutamine daily. For muscle support, 6–10 servings (3–5 g) of L-Leucine may be needed. Split dosing throughout the day may improve tolerability.
- Combine With Protein-Rich Meals Or Resistance Training: Pair leucine intake with protein-containing meals or resistance exercise to maximize muscle protein synthesis. Glutamine is most effective when taken during or after physical stress.
- Monitor For Gastrointestinal Tolerance: High doses of either amino acid may cause bloating or discomfort. Start with 2–3 servings and titrate up as tolerated.
Is it Safe?
This product uses well-tolerated, naturally occurring amino acids with strong safety profiles at these dosages. No proprietary blends obscure labeling, and both ingredients are generally recognized as safe (GRAS) when used appropriately.
Safety & Considerations
- Medical Condition: Avoid in patients with maple syrup urine disease (contraindicated for L-Leucine).
- Medical Condition: Use caution in liver disease or impaired amino acid metabolism (L-Glutamine).
- Drug Interaction: Potential interaction with levodopa; separate dosing by several hours.
Reports for Similar Products
The Science
Efficacy is limited by dose rather than form. While both ingredients are clinically relevant, L-Glutamine at 500 mg provides only 10% of the lower end of the therapeutic range for gut barrier support. Similarly, L-Leucine at 500 mg is only 10–17% of the 3–5 g/day typically used in sarcopenia or muscle synthesis studies. Multiple servings would be required to approach effective levels.
Glutamine supplementation significantly reduces gut permeability in adults in randomized controlled trials.
Glutamine supports immune function and gut barrier integrity via glutathione and heat shock proteins.
Leucine enhances myofibrillar protein synthesis, especially when added to low-protein meals post-exercise.
Meta-analysis showing leucine increases muscle protein synthesis and lean body mass in older adults.
Glutamine enhances exercise-induced plasma IL-6 levels, indicating immunomodulatory activity.
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