Head-to-head evidence comparison — which supplement is right for you?
L-Glutamine wins 1 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
5-10g
Post-workout, Before bed, Or split throughout day
L-Glutamine powder
500-1000mg
With meals, Split doses if taking >500mg
Ascorbic acid or buffered vitamin C
2-4 weeks
2-4 weeks
1-2 weeks
Ongoing
1-2 weeks
4-8 weeks
With high doses (>2g)
Multi-cohort analysis of depression-associated gut bacteria sheds insight on bacterial biomarkers across populations
Cellular and molecular life sciences : CMLS (2022) · Meta analysis · n=1827
By contrast, elevated L-glutamine degradation, and reduced L-glutamate and L-isoleucine biosynthesis were identified in depressive-associated microbiomes.
Metabolomics in Diabetic Retinopathy: A Systematic Review
Investigative ophthalmology & visual science (2021) · Systematic review
This review summarizes potential biomarkers and metabolic pathways, providing insights into new pathogenic pathways for this microvascular complication of diabetes.
L-glutamine supplementation in critically ill patients: A systematic review and meta-analysis
Critical Care Medicine (2020) · Meta analysis · n=4671
Parenteral glutamine reduced infectious complications in ICU patients
Vitamin C supplementation for prevention and treatment of pneumonia
The Cochrane database of systematic reviews (2020) · Meta analysis · n=2774
We are uncertain of the effect of vitamin C supplementation on mortality due to pneumonia (RR 0.21, 95% CI 0.03 to 1.66; 1 study, 57 participants; very low-quality evidence).
Vitamin C supplementation in pregnancy
The Cochrane database of systematic reviews (2015) · Meta analysis · n=20038
Conversely, the risk of term PROM was increased when supplementation included vitamin C and vitamin E (average RR 1.73, 95% CI 1.34 to 2.23; 3060 participants; two studies; I² = 0%).
Enhanced Vitamin C Delivery: A Systematic Literature Review Assessing the Efficacy and Safety of Alternative Supplement Forms in Healthy Adults
Nutrients (2025) · Systematic review
Most studies (77%) had a low risk of bias.
L-Glutamine has a higher evidence score (9/10 vs 8.5/10) and wins in 1 of 3 categories.
For support immune system, Vitamin C has a higher relevance score (85 vs 70).
No known interactions between L-Glutamine and Vitamin C have been documented in our database. However, always consult a healthcare provider before combining supplements.