Labdoor analyzed 14 best-selling glutamine supplements in the United States for glutamine content and heavy metal (arsenic, cadmium, lead, mercury) contamination.
Overall, measured glutamine deviated from label claims by an average of 4.3 %. Products measured an average glutamine concentration of 95.2 %, ranging from 66.3 % to 99.8 %. Research is currently inconclusive about glutamine's effectiveness for exercise performance. Dosing usually begins at 70 mg per kg body weight (4.9 g in a 70 kg individual), although products in this batch do not standardize to this amount in serving size recommendations. All tested products passed heavy metal screens for arsenic, cadmium, lead, and mercury, and recorded glutamine levels per serving well within safe limits.
Analytical Chemistry Methods: HPLC (High Performance Liquid Chromatography) to quantify glutamine levels; ICP-MS (Inductively Coupled Plasma - Mass Spectrometry) to quantify heavy metal (arsenic, cadmium, lead, mercury) load.
Lab-tested glutamine content ranged from -20.7 % to +9.4 % as compared to products’ stated label claims.
Products deviated from label claims by an average of 4.3 %. Powdered products often performed better in label accuracy compared to tablet or capsule forms. Powdered products deviated from label claims for glutamine by an average of 1.6 %. Tablet and capsule products deviated by as much as 20.7 % from glutamine label claims, averaging a deviation of 7.8 % overall.
All 14 products passed heavy metal screens for arsenic, cadmium, lead, and mercury.
All products passed heavy metal screens. This means that each product's heavy metal recordings per serving fell below California Proposition 65's proposed and established MADLs (Maximum Allowable Dose Levels) and NSRLs (No Significant Risk Levels): no more than 10 mcg/day of inorganic arsenic, 4.1 mcg/day of cadmium, 0.5 mcg/day of lead, and 0.3 mcg/day of mercury (proposed).
Glutamine products averaged a 9.99 (out of 10) in Nutritional Value scores.
Glutamine products in this batch recorded minimal quantities of calories, fats, carbohydrates, and sugars.
No flagged sweeteners, coloring agents, or preservatives were recorded in this batch analysis.
All products in this batch analysis recorded safe levels of glutamine per serving. Currently, glutamine does not have an established Tolerable Upper Intake Level (UL). Glutamine appears to be safe even up to 0.65 g per kg body weight (45.5 g for a 70 kg individual) with no reported serious side effects in clinical study. People with liver, renal, or psychiatric health concerns should consult a physician before consuming large doses of supplementary amino acids like glutamine.
No synthetic sweeteners, artificial colors, or controversial preservatives were recorded in this batch of products.
Tablet and capsule products recorded the lowest glutamine concentrations in this batch, with as little as 0.663 g of glutamine per 1 g of product.
Concentrations of glutamine averaged 95.2 %, ranging from 66.3 % in Jarrow Formulations to 99.8 % in Body Fortress Glutamine Powder. Tablet and capsule formulations generally had less pure formulations of glutamine. The average glutamine concentration in tablet and capsule formulations was 90.9 %, compared to 98.4 % in powdered products.
Glutamine content per serving ranged from 547 mg to 5920 mg. Serving size recommendations are not standardized. 10 of the 14 products recommended serving sizes below 5 g, the lowest dose at which glutamine has been found to be effective in research.
Research is inconclusive about the effectiveness of glutamine supplementation for exercise. A few studies have shown that glutamine supplementation as low as 70 mg per kg body weight (4.9 g in a 70 kg individual) improved performance and recovery by increasing muscle glycogen concentrations after exhaustive exercise. However, other studies with up to 45 g of glutamine for 6 weeks concluded that glutamine was no more effective than placebo.
Research shows that exhaustive exercise lowers glutamine levels and immune defenses. 5 g of glutamine right after exhaustive exercise and then 2 hours after that has been shown in one study to boost the immune system, which reduced infection rates the following week compared to placebo.