D-Glutamine is the D-type stereoisomer of cell-permeable glutamine, one of the 20 amino acids encoded by the standardized genetic code.

In catabolic states of injury and illness, glutamine becomes conditionally-essential (requiring intake from food or supplements). Glutamine is the most abundant naturally occurring, non-essential amino acid in the human body and one of the few amino acids that can directly cross the blood–brain barrier. [1] Glutamine is a key pharmaconutrient in the body's response to stress and injury. Glutamine exerts its protective effects via multiple mechanisms, including direct protection of cells and tissue from injury, attenuation inflammation, and preservation of metabolic function. [1]

Glutamine shows the greatest benefit when administered at doses greater than 0.35 g/kg/day, with optimal benefit potentially occurring at 0.5 g/kg/day. [2]

Effect of D-Glutamine and glutaminase inhibitor on acetaldehyde-induced permeability. Caco-2 cell monolayers are incubated for 4 h without or with acetaldehyde (600 μM) and L-Glutamine or D-Glutamine (2 mM) in the absence or presence of 6-diazo-5-oxo-L-norleucine (DON). Transepithelial electrical resistance (TER) and FITC-inulin flux are measured. Values are means±SE (n=6)[2].