Glutamine

Glutamine is one of the conditionally essential amino acids1. Under normal circumstances, the body makes enough. In certain instances, such as a critical illness, the body’s requirement exceeds its production capability. In these times, the body needs an external (dietary/supplement) source, to meet its needs2.

Amino Acids 101: Essential vs Non-Essential vs Conditionally Essential

Proteins are made from amino acids linked together in a chain of varying lengths. There are 21 amino acids we need. Of those, there are essential, non-essential, and conditionally essential amino acids. Essential amino acids are ones the body lacks the ability to make on its own. We need to get essential amino acids from food. The body has the ability to make non-essential amino acids on its own. We do not need to eat non-essential amino acids to survive. In certain circumstances, the body cannot make enough of a certain amino acid; these are known as conditionally essential1.

Purported Benefits of Glutamine

Glutamine is a popular supplement. It’s available as an individual amino acid or as part of a protein supplement. Product labels tout its many benefits including: increased protein synthesis, support of muscle recovery, boosted immune system, and decreased soreness.

What does the research say about glutamine’s benefits?

Body Composition, Muscular Strength, Muscular Endurance, and Performance

Study 1. This study examined the effects of creatine, ribose, and glutamine supplementation on muscular strength, endurance, and body composition. Twenty eight men participated for eight weeks. They were split into a placebo group and a supplement3.

Results:

  • Body Weight Average
    • Supplement Group: before – 194 pounds/after- 198 pounds
    • Placebo Group: before – 182.4 pounds/after – 182.6
  • Body Fat Percentage Average
    • Supplement Group: before – 12.3%/after – 11.9%
    • Placebo Group: before – 13.5%/after – 12.2%
  • Muscular Strength –  bench press 1 repetition max (1-RM)
    • Supplement Group: before – 263.9 pounds/after- 285.9 pounds
    • Placebo Group: before – 247.6 pounds/after 262.4
  • Muscular Endurance – bench press as many repetitions as possible at 80% of 1-RM
    • Supplement Group: before – 8.1 reps/after- 10.9 reps
    • Placebo Group: before – 7.4 reps/after 10.2 reps

Both groups saw improvements in body fat percentage, muscular strength, and muscular endurance. The researchers concluded that using a supplement containing creatine, ribose, and glutamine did not enhance muscular strength, endurance, or body composition. In this study, researchers were looking at a combination of three supplements rather than only glutamine. There were no significant differences between either group in the results. If glutamine was effective, the results would have shown an improvement in the supplement group3.

Study 2. The next study looked at the effects of glutamine supplementation on muscle protein degradation, muscular strength, and body composition. This study had 31 participants that were split into a supplement group and a placebo group. The supplement group was given 0.41 grams of glutamine per pound of lean body mass per day for six weeks. Both groups participated in a total body resistance training program4.

The results showed glutamine did not significantly improve results over the placebo. The glutamine group showed a 6% increase in knee extension torque, a 2% increase in lean body mass, and a 41% increase in urinary excretion of 3-methylhistidine (a marker of protein degradation). The placebo group showed a 5% increase in knee extension torque, a 1.7% increase in lean body mass, and a 56% increase in 3-methylhistidine excretion. The glutamine strength and lean body mass numbers were insignificantly better than the placebo group. The glutamine group did have decreased protein breakdown4.

Recovery from Exercise

A 1999 study looked at the effects of glutamine on carbohydrate storage and glycogen resynthesis after exercise. Subjects participated in a glycogen depleting exercise routine and then consumed one of three drinks: glucose drink, glucose drink with 8 grams of glutamine, or 8 grams of glutamine with no glucose. The results showed the consumption of a glutamine-only or glucose-only drink increased glycogen resynthesis to similar levels. Researchers concluded that consuming glutamine and glucose following exercise, “resulted in a greater storage of carbohydrate5.”

Decreased Post-Exercise Soreness

This study examined the effects of glutamine supplementation on markers of recovery. Fifteen participants were split between a glutamine and placebo group. Both groups performed 100 drop jumps. They were then either given maltodextrin or a maltodextrin/glutamine mix 0, 24, 48, and 72 hours following exercise. Subjects’ knee extensor concentric peak torque and perceived muscle soreness were measured at 0, 1, 24, 28, 72, and 96 hours following the exercise6.

Results showed the glutamine group preserved more strength following the drop jumps and had a decrease in perceived muscle soreness. Researchers concluded glutamine was effective in preserving strength and easing muscle soreness post exercise6.

Immune System

Athletes participating in high intensity or lengthy exercise are at an increased risk of infection. Glutamine is an energy source for some cells in the immune system. Exercise decreases plasma glutamine concentrations when these cells need energy the most. This study split athletes from various sports(middle distance runners, marathon runners, ultra-marathon runners, and elite rowers) into placebo and glutamine supplementation groups. The study found glutamine supplementation appeared to have a beneficial effect on the amount of post-exercise infections. Additionally, groups on a glutamine supplement increased their ratios of T-helper/T-suppressor cells (indicating a stronger immune system) compared to the placebo group7.

The Bottom Line

The research on glutamine is at best, mixed. The first two studies did not show much difference between the supplement and placebo groups. The other studies did show glutamine possibly increases post-exercise glycogen resynthesis, decreases soreness, and may prevent exercise-induced infections. Many protein supplements already contain varying amounts of glutamine, making additional supplementation unnecessary. At this time, the research does not make the case glutamine is an extremely beneficial product for the vast majority of individuals.

References

  1. Amino acids. (n.d.). Retrieved from https://medlineplus.gov/ency/article/002222.htm
  2. Lacey, J. M., & Wilmore, D. W. (1990). Is glutamine a conditionally essential amino acid? Nutrition Review, 48(8), 297-309. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/2080048
  3. Falk, D. J., & Heelan, K. A. (2003). Effects of Effervescent Creatine, Ribose, and Glutamine Supplementation on Muscular Strength, Muscular Endurance, and Body CompositionThe Journal of Strength and Conditioning Research, 17(4), 810. doi:10.1519/1533-4287(2003)0172.0.co;2
  4. Candow, D., & Chilibeck, P. (2001). Effect of glutamine supplementation combined with resistance training in young adultsEuropean Journal of Applied Physiology, 86(2), 142-149. doi:10.1007/s00421-001-0523-y
  5. Bowtell, J. L., & Gelly, K. (1999). Effect of oral glutamine on whole body carbohydrate storage during recovery from exhaustive exerciseJournal of Applied Physiology, 86(6), 1770-1777. doi:10.1152/jappl.1999.86.6.1770
  6. Street, B., & Byrne, C. (2011). Glutamine Supplementation in Recovery From Eccentric Exercise Attenuates Strength Loss and Muscle SorenessJournal of Exercise Science & Fitness, 9(2), 116-122. doi:10.1016/s1728-869x(12)60007-0
  7. Castell, L. M., & Newsholme, E. A. (1997). The effects of oral glutamine supplementation on athletes after prolonged, exhaustive exerciseNutrition, 13(7-8), 738-742. doi:10.1016/s0899-9007(97)83036-5
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