L-Glutamine for Immune Function

Research suggests that L-glutamine plays a meaningful role in supporting immune function across several contexts, with the strongest mechanistic evidence coming from in vitro work showing that glutamine availability directly influences macrophage activity, including phagocytosis and immune signaling, and that deficiencies seen in conditions like burns, sepsis, and surgery may contribute to immune suppression. Clinical support comes from a randomized controlled trial in athletes showing higher salivary immunoglobulin A levels and fewer upper respiratory infections with supplementation, as well as an RCT in cardiac surgery patients using a glutamine-containing combination supplement that showed reduced complications and organ failure scores, and a clinical trial in severe pancreatitis patients showing improved immune markers and fewer infectious complications. However, findings are not uniformly positive — a 2008 review concluded that supplementation in healthy, well-nourished athletes did not meaningfully prevent exercise-related immune changes because post-exercise glutamine drops are unlikely to reach levels low enough to impair immune cell function, and a rat study found that glutamine supplementation during moderate exercise training offered no immune benefit and may have reduced certain immune cell activities. Taken together, the evidence from this mix of randomized trials, reviews, and mechanistic studies suggests that glutamine's immune-related benefits may be most relevant in states of physiological stress, illness, or critical care, while its utility for healthy individuals engaged in routine exercise remains less clearly established.