L-Glutamine + L-Leucine by California Gold Nutrition is a dual-action amino acid supplement designed to support both gastrointestinal and muscular health. The formulation delivers 2.5 grams each of L-Glutamine and L-Leucine per serving, two conditionally essential and essential amino acids, respectively, that play distinct but complementary physiological roles. As a supplement, it is intended for oral use and fits within the context of sports nutrition, gut health support, and age-related muscle preservation.
The primary focus of this product lies in its named ingredients—both of which are classified as primary due to their equal dosing and prominence in the product title. L-Glutamine is a well-researched amino acid critical for enterocyte fuel and immune cell metabolism, particularly during physiological stress. L-Leucine, a branched-chain amino acid (BCAA), is a potent stimulator of the mTOR pathway, driving muscle protein synthesis. The efficacy of this product hinges on whether these ingredients are delivered at doses shown in clinical research to elicit functional benefits, particularly in target populations such as active individuals, older adults, or those with increased metabolic demands.
Quick Summary
Full transparency: both ingredients are listed with exact amounts, and there are no proprietary blends or hidden fillers.
Moderate efficacy: both primary ingredients are below clinical midpoints (50–62.5%), but L-Leucine is closer to effective dosing. At 2 servings (5 g total), both ingredients reach clinically relevant levels, supporting gut and muscle function in target populations.
Both L-Glutamine and L-Leucine are in free-form powder, which is rapidly absorbed in the small intestine. This form is considered highly bioavailable, especially in unflavored, additive-free formulations like this one.
Generally safe for healthy adults, but contraindications exist for maple syrup urine disease and critical illness. Leucine may interact with levodopa, and glutamine should be used cautiously in liver or kidney disease.
Suggested: 2 servings/day to reach clinical midpoint
Why Take This Product
Key Benefits
- Supports Gut Barrier Integrity: L-Glutamine serves as a primary fuel source for intestinal epithelial cells and has been shown in randomized controlled trials to significantly reduce gut permeability in adults, supporting mucosal health and reducing leaky gut risk [1].
- May Improve Recovery from Intense Exercise: Glutamine supports immune cell function and may modulate post-exercise inflammation, while leucine directly supports muscle repair. Together, they may help maintain immune and muscular function during periods of high training volume [8].
Who Should Take This
Potential Side Effects
Ingredient Breakdown
Each ingredient is provided in free-form, unbound amino acid powder, which allows for rapid gastrointestinal absorption and bioavailability. Both are synthetic but bioidentical to endogenous forms.
Primary Ingredients
L-Glutamine
Gut barrier support, immune modulation, antioxidant synthesis
Dose is 50% of the clinical midpoint (7.5 g). While safe and beneficial for gut health in non-critical adults, 2.5 g is sub-therapeutic for most clinical indications. May still provide mild support, especially when combined with dietary sources.
A conditionally essential amino acid that fuels enterocytes and immune cells, supports gut integrity, and enhances glutathione production. Shown to reduce intestinal permeability in adults [1].
L-Leucine
Muscle protein synthesis stimulation via mTOR activation
Dose is 62.5% of the clinical midpoint (4 g). While below the upper end of therapeutic dosing, 2.5 g is within the effective range, particularly when combined with protein intake or resistance training. Considered partially effective.
An essential branched-chain amino acid that acts as both a substrate and signaling molecule for muscle anabolism. Effective in improving lean mass and strength in older adults and athletes [2][3].
Practical Recommendations
- Optimize Timing For Muscle Support: Take 2.5–5 g of leucine around resistance exercise (pre- or post-workout) to maximize muscle protein synthesis, especially if total protein intake is low.
- Support Gut Health During Stress: Glutamine may be most beneficial when taken during periods of intense training, gastrointestinal discomfort, or recovery, with doses of 5–10 g/day often used clinically.
- Consider Stacking With Complete Protein: Leucine works best in the context of adequate total protein intake. Pair this supplement with a balanced diet to avoid isolated amino acid imbalances.
Is it Safe?
The product contains no proprietary blends, and full dosing is disclosed. While both ingredients are safe for most adults, specific contraindications exist for certain medical conditions, particularly maple syrup urine disease and critical illness.
Safety & Considerations
- Medical Condition: Avoid in maple syrup urine disease (MSUD) due to impaired leucine metabolism.
- Medical Condition: Avoid parenteral glutamine in critically ill patients; enteral use appears safer but clinical benefit is uncertain in ICU settings.
- Drug Interaction: Leucine may compete with levodopa for absorption; separate dosing by at least 2–3 hours in Parkinson’s patients.
- Medical Condition: Use caution in liver disease or impaired amino acid metabolism; both amino acids are metabolized hepatically.
Reports for Similar Products
The Science
Efficacy is determined by whether primary ingredients are present at doses shown in clinical trials to produce measurable physiological effects. L-Glutamine and L-Leucine are both primary ingredients, and their effectiveness depends on achieving sufficient plasma concentrations to influence gut and muscle metabolism.
Glutamine supplementation significantly reduces gut permeability in adults in randomized controlled trials.
Meta-analysis found leucine increases muscle protein synthesis and lean body mass in older adults.
Leucine supplementation showed beneficial effects on sarcopenia criteria, including lean mass and physical performance.
Glutamine is conditionally essential in catabolic states due to increased demand and depleted stores.
Glutamine supports immune function and gut barrier integrity, possibly via glutathione and heat shock proteins.
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