Is Glutamine Worth Your Money?
The supplement industry is booming! Product labels are more colorful and promises of drastic body composition changes are more extreme than ever before. Of course, it wouldn't be socially responsible for supplement companies to make completely unfounded claims.
The bright people running those companies found a solution to that problem: run their own research and report whatever results will benefit their bank accounts. Combine this with the mass media and a number of "fitness professionals" frequently misquoting or misinterpreting research and you have a recipe for confusion, disappointment and wasted money.
I don't want to make it seem like all companies and professionals are out to allude the general public. There are certainly excellent researchers, writers, and speakers that have done their homework and lack ulterior motives (Cassandra Forsythe and John Berardi come to mind).
Unfortunately, quality information on supplements can be hard to find for those that don't have the time or know-how to critically analyze relevant research. With supplements increasing in popularity over the last decade, there is a need to bridge the gap between the supplement-market and quality research describing the safety and efficacy of the supplements.
What Is Glutamine?
In the body, glutamine serves to increase cell volume, and stimulate protein and glycogen synthesis.1-5 Furthermore, glutamine can be used as a fuel for the immune system (lymphocytes and macrophages)5-9 and is involved in growth hormone secretion, collagen formation, and renal acid excretion.10-13
At this point, it isn't hard to see the attraction with glutamine supplementation. It would appear that supplemental glutamine would have the potential to make you bigger and stronger, as well as facilitate a more rapid recovery.14,15
This latter idea is supported by the fact that plasma and muscle glutamine levels are suppressed following bouts of intense training making glutamine "conditionally essential".6-8
Basically, the thought is that supplemental glutamine would allow you to train at high levels while avoiding, or at least minimizing the deleterious effects of overtraining.
Unfortunately, concrete evidence supporting the proposed benefits of glutamine supplementation is lacking. Research has yet to provide strong support for additional glutamine attenuating immune suppression induced by exercise or other stressors.5,7,17
Furthermore, there does not appear to be any advantage of glutamine supplementation with regards to glycogen synthesis if adequate dietary carbohydrates are consumed.5
Contrary to the previous scholarly skepticism, one study actually found that 10 weeks of resistance training accompanied by supplementation with a whey protein drink enriched with 5g of glutamine and 3g of branched chain amino acids (BCAAs) resulted in a greater increase in strength and lean muscle mass compared to just a whey protein drink alone (both groups underwent the same training program).18
This would appear to be good news for lifting and supplement enthusiasts. While I don't think it's logical to completely dismiss these results, it should be noted that it is impossible to determine whether the experienced benefit was due to the glutamine, the BCAA, or the combination of the two.
Should You Be Taking It?
Despite a seemingly large body of evidence negating the effectiveness of glutamine supplementation, I'm not sure it's appropriate to write the supplement off altogether.
As much as I rely on research to support the use of ergogenic aids, every research study has its limitations. Many studies have no or a poorly designed control group, fail to account for important lifestyle factors, or do not provide a sufficient training stimulus to elicit a training effect (or sufficient stress to measure the effect of a supplement).
Also, because immune system suppression is largely a characteristic of endurance training, high-quality research on resistance training is relatively limited.
If you're interested in taking glutamine there are a few things you should be aware of. Timing is important. One study found that plasma glutamine levels were 19% higher when the supplement was given immediately post-exercise, opposed to three hours later.19
Similar to protein drinks in general, it appears that consuming glutamine either during or immediately following training will provide the greatest benefit, in this case increase in serum glutamine concentration.
Anytime you consider taking a supplement, it's important to consider possible side effects. Glutamine supplementation of 20-30g in healthy adults, 28g/day for 14 days in athletes, and 0.65g/kg body weight in patients has been reported to be safe.20 Despite the reported safety of these higher doses, the typical recommendation is 5g of glutamine immediately following exercise.
Regardless of what the research says, I break supplementation down into two basic questions:
- Is it safe?
- Does it work?
Should you take glutamine? That's up to you. With a price as low as $0.03/gram, it's a relatively cheap supplement. Research hasn't supported an ergogenic benefit in healthy adults, but that isn't to say there isn't one, or that you won't experience one.
It's possible that the small benefit documented in the research literature, and the short-term nature of the majority of the studies simply doesn't allow enough time for the benefits to reach statistical significance.
I've taken glutamine for various reasons. Because of it's established safety, the only thing you have to lose is some money. I'm a big fan of self-experiments. Different things work for different people.
Give it a shot and note whether you experience an effect or not. If you do, try taking it again. If you don't, then scrap it. In general, I support the use of supplements, but they're just icing on the cake. Remember, you can't out-supplement a bad training program.
- Low, S.Y., Taylor, P.M., & Rennie, M.J. (1996). Responses of glutamine transport in cultured rat skeletal muscle to osmotically induced changes in cell volume. The Journal of Physiology, 492, 877-85.
- Rennie, M.J., Khogali, S.E., Low, S.Y., et al. (1996). Amino acid transport in heart and skeletal muscle and the functional consequences. Biochemical Society Transactions, 24, 869-873.
- Rennie, M.J., Ahmed, A., Khogali, S.E., Low, S.Y., Hundal, H.S., & Taylor, P.M. (1996). Glutamine metabolism and transport in skeletal muscle and heart and their clinical relevance. The Journal of Nutrition, 126, 1142S-1149S.
- Varnier, M., Leese, G.P., Thompson, J., & Rennie, M.J. (1995). Stimulatory effect of glutamine on glycogen accumulation in human skeletal muscle. The American Journal of Physiology, 269, E309-315.
- Williams, M. (2005). Dietary Supplements and Sports Performance: Amino Acids. Journal of the International Society of Sports Nutrition, 2, 63-67.
- Filaire, E., Lac, G., & Pequignot, J.M. (2003). Biological, hormonal, and psychological parameters in professional soccer players throughout a competitive season. Perceptual and Motor Skills, 97, 1061-1072.
- Buchman, A.L. (2001). Commercially essential or conditionally essential? A critical appraisal of the human data. American Journal of Clinical Nutrition, 74, 25-32.
- Miles, M.P., Naukam, R.J., Hackney, A.C., et al. (1999). Blood leukocyte and glutamine fluctuations after eccentric exercise. International Journal of Sports Medicine, 20, 322-327.
- Rowbottom, D.G., Keast, D., Morton, A.R. (1996). Sports Medicine, 21, 80-97.
- Curi, R., Lagranha, C.J., Doi, S.Q., et al. (2005).Glutamine-dependent changes in gene expression and protein activity. Cell Biochemistry and Function, 23, 77-84.
- Karna, E., Miltyk, W., Wolczynski, S., et al. (2001). The potential mechanism for glutamine-induced collagen biosynthesis in cultured human skin fibroblasts. Comparative Biochemistry and Physiology, Biochemistry, and Molecular Biology, 130, 23-32.
- Welbourne, T., Claville, W., & Langford, M. (1998). An oral glutamine load enhances renal acid secretion and function. The American Journal of Clinical Nutrition, 67, 660-663.
- Welbourne, T.C. (1995). Increased plasma bicarbonate and growth hormone after an oral glutamine load. The American Journal of Clinical Nutrition, 61, 1058-1061.
- Kreider, R.B. (1999). Dietary supplements and the promotion of muscle growth with resistance exercise. Sports Medicine, 27, 97-110.
- Antonio, J., & Street, C. (1999). Glutamine: a potentially useful supplement for athletes. Canadian Journal of Applied Physiology, 24, 1-14.
- Nieman, D.C. (2000). Is infection risk linked to exercise workload? Medicine and Science in Sports and Exercise, 32, S406-411.
- Gleeson, M., Lancaster, G.I., & Bishop, N.C. (2001). Nutritional strategies to minimise exercise-induced immunosuppression in athletes. Canadian Journal of Applied Physiology, 26, S23-35.
- Colker, C.M. (2000). Effects of supplemental protein on body composition and muscular strength in healthy athletic male adults. Current Therapeutic Research, 61, 19-28.
- Levenhagen, D.K., Gresham, J.D., Carlson, M.G., Maron, D.J., et al. (2001). Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis. American Journal Physiology, Endocrinology and Metabolism, 280, E982-E993.
- Gleeson, M. (2008). Dosing and efficacy of glutamine supplementation in human exercise and sport training. Journal of Nutrition, 138. 2045S-2049S.