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Abstract
Some athletes can have high intakes of L-glutamine because of their high energy and protein intakes and also because they consume protein supplements, protein hydrolysates, and free amino acids. Prolonged exercise and periods of heavy training are associated with a decrease in the plasma glutamine concentration and this has been suggested to be a potential cause of the exercise-induced immune impairment and increased susceptibility to infection in athletes. However, several recent glutamine feeding intervention studies indicate that although the plasma glutamine concentration can be kept constant during and after prolonged strenuous exercise, the glutamine supplementation does not prevent the postexercise changes in several aspects of immune function. Although glutamine is essential for lymphocyte proliferation, the plasma glutamine concentration does not fall sufficiently low after exercise to compromise the rate of proliferation. Acute intakes of glutamine of ∼20–30 g seem to be without ill effect in healthy adult humans and no harm was reported in 1 study in which athletes consumed 28 g glutamine every day for 14 d. Doses of up to 0.65 g/kg body mass of glutamine (in solution or as a suspension) have been reported to be tolerated by patients and did not result in abnormal plasma ammonia levels. However, the suggested reasons for taking glutamine supplements (support for immune system, increased glycogen synthesis, anticatabolic effect) have received little support from well-controlled scientific studies in healthy, well-nourished humans.
Abbreviations
bm
body mass
URTI
upper respiratory tract infection
V̇O2 max
maximum oxygen uptake
1
Published in a supplement to The Journal of Nutrition. Presented at the conference “The Seventh Workshop on the Assessment of Adequate and Safe Intake of Dietary Amino Acids” held November 2–3, 2007 in Tokyo. The conference was sponsored by the International Council on Amino Acid Science (ICAAS). The organizing committee for the workshop was David H. Baker, Dennis M. Bier, Luc A. Cynober, Yuzo Hayashi, Motoni Kadowaki, Sidney M. Morris Jr, and Andrew G. Renwick. The supplement coordinators were David H. Baker, Dennis M. Bier, Luc A. Cynober, Motoni Kadowaki, Sidney M. Morris Jr, and Andrew G. Renwick. Supplement coordinator disclosures: all of the coordinators received travel support from ICAAS to attend the workshop.
2
Author disclosures: M.Gleeson, the ICAAS paid the author’s travel expenses to attend the meeting.
Copyright © 2008 American Society for Nutrition. Published by Elsevier Inc. All rights reserved.