Glutamine

What glutamine does in your body

Glutamine is the most abundant free amino acid in your bloodstream and muscle tissue. Your body produces it naturally from glutamate and ammonia through the enzyme glutamine synthetase. Under normal conditions, you make about 50-80 grams per day, mostly in your skeletal muscle ^[1]. Your intestines, kidneys, and immune cells consume this glutamine constantly to fuel their rapid turnover and activity.

We call glutamine 'conditionally essential' because while your body normally produces enough, certain situations push demand beyond supply. Heavy exercise, surgery, burns, sepsis, or chronic illness can all deplete glutamine stores by 20-50% ^[2]. When this happens, your muscles break down to release more glutamine, creating a catabolic state that works against muscle preservation and recovery.

Muscle recovery and exercise performance

Intense exercise drops blood glutamine levels significantly. A single marathon can reduce plasma glutamine by 20% for several days ^[3]. This matters because glutamine supports protein synthesis and reduces muscle protein breakdown. Studies show that athletes supplementing with glutamine (0.3-0.5 g/kg body weight) experience faster recovery of muscle glycogen and reduced markers of muscle damage after exhaustive exercise ^[4].

The evidence for strength gains is more mixed. While glutamine supports the anabolic environment, it does not directly stimulate muscle protein synthesis the way leucine does. Its main benefit comes from reducing catabolism and supporting immune function during high-volume training blocks when overtraining risk peaks.

Gut barrier function and digestive health

Your intestinal lining completely replaces itself every 3-5 days, requiring enormous energy and raw materials. Glutamine is the primary fuel source for enterocytes, the cells lining your intestines ^[5]. Without adequate glutamine, these cells cannot maintain tight junctions, the protein structures that hold intestinal cells together and prevent unwanted substances from leaking into your bloodstream.

Research shows glutamine supplementation helps maintain intestinal barrier integrity during stress. In critically ill patients, glutamine reduces markers of intestinal permeability and bacterial translocation ^[6]. For people with irritable bowel syndrome or inflammatory bowel disease, glutamine may help reduce gut permeability and associated symptoms, though results vary by individual.

Immune system support

Immune cells consume glutamine at rates comparable to or exceeding glucose when activated. Lymphocytes, macrophages, and neutrophils all rely on glutamine for rapid proliferation and function ^[7]. During infection or intense training, this demand spikes sharply.

Studies in endurance athletes show glutamine supplementation reduces infection rates during heavy training periods. One trial found that runners taking glutamine had significantly fewer upper respiratory tract infections during a 12-week training block compared to placebo ^[8]. The effect is most pronounced when baseline glutamine levels are low due to training stress.

When to consider supplementation

Most people get enough glutamine from a protein-rich diet. Meat, fish, eggs, dairy, beans, and cabbage all provide significant amounts. However, supplementation makes sense in specific situations: during high-volume training blocks (more than 10 hours per week), after major surgery or trauma, during recovery from burns, or when experiencing chronic digestive issues. A typical dose ranges from 5-10 grams daily, taken post-workout or between meals.