Suggestions for future research
It is obvious that more studies are needed, but it may not currently be possible to randomize patients to be given extra glutamine. At least, it cannot be considered ethical to give glutamine supplementation without monitoring plasma concentrations. However, quite large doses can be given enterally with only marginal effect on plasma concentration. Still toxic? Obviously more observational studies are needed and in addition the toxicity of glutamine must be characterized. Is the toxicity related to plasma concentration?