Glutamine supplements have been on the market
since the 1990s. There has been great debate and discussion as
to the effects of this supplement on human performance. Glutamine
has commonly been known to aid athletes in several key forms.
First, many believe that glutamine can play a considerable role
in supporting a healthy immune function. This is especially true
in athletes who may have a tendency to overtrain. This is of
great importance as most athletes throughout the year can easily
overtrain which often leads to sickness and a significant decrease
in performance. Many companies also claim that glutamine aids
in the storage and production of glycogen. This can be of key
importance to most endurance athletes as well as to a high number
of endurance oriented anaerobic athletes. Lastly, glutamine has
been known for its anabolic effects of enhancing strength and
muscle mass. It is often known around the bodybuilding world
as a highly anabolic substance that greatly reduces catabolism
and protein degradation. Many theories also advocate that glutamine
may play a role in promoting an advantageous environment for
heightened levels of growth hormone during intense levels of
Although the research is somewhat split around the supplementation
of glutamine and its positive effects, there are many studies
which show conclusive evidence pertaining to the effectiveness
of orally ingesting glutamine. In a study performed by Welbourne
et al (1), subjects who orally ingested only 2 grams of glutamine
increased plasma bicarbonate levels in the body. Increased levels
of plasma bicarbonate have been shown to improve one's ability
to buffer lactic acid thus, increasing performance.
One of the most profound studies (2) performed on glutamine dealt
with a very unique muscle regulator known as myostatin which
is commonly produced by glucocorticoids. This substance may be
one of the key factors that helps determine one's genetic potential
for gaining muscle mass and strength. Specifically, moderate
to high levels of myostatin may cause glucocorticoid muscle atrophy
in healthy humans. In this specific study performed by Salehian
et al (2), glutamine was found to prevent glucocorticoid induced
muscle atrophy. In other words, this study showed that administration
of glutamine provided a potential mechanism for the prevention
of muscle atrophy induced by glucocorticoids and myostatin. Also,
those who received glutamine had significantly less reductions
in body and muscle weights and lower myostatin expression than
the placebo group.
In a study by Lacey et al (3), short-term glutamine ingestion
had no effect on muscular strength; however, long-term supplementation
showed to be a more effective application of glutamine in regards
to strength gains. Furthermore, other studies have shown that
glutamine causes positive effects on performance due to a plethora
of physiological events which include increased levels of growth
hormone, decreased catabolic effects of skeletal muscle, increased
anabolic effects, enhanced protein synthesis, and greater ability
to sustain high intensity exercise due to the increased capability
of buffering lactic acid.
Glutamine has also been shown to dramatically enhance immune
system function for athletes and healthy adults who train at
high enough intensities that typically trigger a breakdown in
the immune system (4). From the medical literature, glutamine
may have a place in the dietary regimen of athletes undergoing
intense exercise training and possibly have a role in maintaining
optimal health during the competitive season via benefits to
the immune system (5).
Glutamine's effect on the immune system may also be witnessed
by examining data on hospital patients supplementing glutamine
in order to ward off any potential sicknesses associated with
surgery or hospital stays. In a very recent study performed by
Oquz et al (10), patients undergoing colorectal surgery for cancer
were observed over a five year period. Half of the patients received
glutamine treatment within their nutrition during their hospital
stay and the other half did not. After results were analyzed,
it appeared as though the group which received glutamine supplementation
had less complications after their operation and a shorter hospital
stay than those who were not administered the glutamine supplementation.
Many other studies also support glutamines use on immune system
function, although not directly related to athletes. In a study
performed by Fuentes et al (11), glutamine supplementation appears
to improve infectious morbidity of hospitalized patients by improving
host defenses and other immune system responses. In another study
performed by Li et al (12), it appears as though premature infants
given intravenous glutamine supplementation spend fewer days
in the hospital and also have a decreased rate of hospital related
Although many studies on glutamine supplementation and immune
response are not performed directly on athletes, this does not
suggest that these findings cannot be of great importance to
athletes. In fact, exercise in and of itself can be a mild to
somewhat intense form of stress and trauma on the body which
may heavily tax the immune system. Although not as severe as
surgical procedures performed on hospitalized patients, athletes
undergoing intense training may find that glutamine does have
a positive effect on immune system function.
As previously mentioned, there is an increased risk of infections
in athletes undertaking prolonged, strenuous exercise. There
is also some evidence that cells of the immune system are less
capable of producing a defense against infections after such
exercise. The level of plasma glutamine, an important fuel for
cells of the immune system, is decreased in athletes after endurance
exercise. This may be partly responsible for the apparent immuno-suppression
which occurs in these individuals. In one of the more conclusive
studies done on glutamine by Castell et al (7), oral consumption
of glutamine after intense exercise was examined in elite runners
and rowers. Most of these athletes were endurance oriented. The
results of the study indicate that there was a significant decrease
in infections and illness after intense training in those who
supplemented with glutamine versus those who did not. Glutamine's
role in enhancing immune system function seems to be highly conclusive
in this study.
Candow et al (6) assessed the effect of oral glutamine supplementation
combined with resistance training in young adults. Strength and
muscular skeletal markers were examined before and after the
six week study in both the placebo and experimental group. It
appears as though there was a slight increase in one repetition
squat, force production in the knee extensor, and lean muscle
mass. Although these numbers were slightly higher than the placebo
group, they were not enough to be a "significant" difference.
It must be noted that many world class athletes may work years
for small increases in performance that may or may not seem "significant"
to those in a laboratory setting but may be of utmost importance
to the elite athlete. However, to the average weightlifter, results
from this specific study may not warrant supplementation with
In regards to the proper and effective dosage of glutamine, research
is quite varied. Some researches such as Van Gammeren et al (8)
have shown success with as low as 2 grams of glutamine per day.
While yet, other scientists such as Candow et al (6) administered
substantially greater levels of glutamine to their subjects with
as much as 45 grams of glutamine per day. However, the majority
of studies as noted by Hultman et al (9) suggest that 4-10 grams
per day will suffice for optimal physiological gains from glutamine
supplementation. Yet, there are a host of others that would suggest
up to 20 grams per day. The most extreme levels of glutamine
supplementation can be seen in studies dealing with hospitalized
patients. In fact, in the study performed by Oquz et al (10),
patients received 1g/kg/day, which could be anywhere between
50-120 grams per day depending on body weight. It also appears
from the previously mentioned studies that glutamine supplementation
is far more effective when used long term rather than short term.
Summary and Recommendation
Although further evidence would help support supplementation
with glutamine to an even higher degree, there is considerable
research to warrant its usage among many high performance athletes.
The benefits as previously noted includes: supporting a healthy
immune system, less reduction in body and muscle weights, lower
myostatin expression, increased levels of growth hormone, decreased
catabolic effects of skeletal muscle, increased anabolic effects,
increased protein synthesis, and greater ability to sustain high
intensity exercise due to the increased capability of buffering
lactic acid. All these factors could potentially lead to increases
in muscle mass, strength, and power.
The recommended dosage for glutamine is 5-20 grams per day. There
are claims that even higher dosages may be more effective, but
further evidence is needed. However, there have been studies
demonstrating that 40 grams a day has no safety or toxicity concerns.
Therefore, toxicity is not an issue with glutamine supplementation.
Distributing glutamine throughout the day in smaller dosages
is also recommended. A common glutamine supplementation protocol
is 5 grams in the morning, 5 grams pre-workout, followed by 5
grams post workout, with an optional 2-5 gram dosage before bed.
Similar guidelines and dosage amounts are recommended for non-workout
According to consumerlab.com and other valid sources, some of
the best glutamine products on the market include: Dymatize Proline
Micronized Glutamine, Effervescent Glutamine, Puritan's Pride
L-Glutamine, AST Glutamine, Beverly International Glutamine Select
Plus BCAAs, and Precision Engineered Pure L-Glutamine.
1. Welbourne, T. Increased plasma bicarbonate and growth hormone
after an oral glutamine load. Am. J. Clin. Nutr. 61:1058-1061.
2. Salehian B, Mahabadi V, Bilas J, Taylor WE, Ma K. The effect
of glutamine on prevention of glucocorticoid-induced skeletal
muscle atrophy is associated with myostatin suppression. Metabolism.
2006 Sep; 55: 1239-47.
3. Lacey, J.M., and D.W. Wilmore. Is glutamine a conditionally
essential amino acid? Nutr. Rev. 48:297-309. 1990.
4. Perriello, G., N. Nurjhan, and M. Stumvoll. et al. Regulation
of gluconeogenesis by glutamine in normal post-absorptive humans.
Am. J. Physiol. 272:E437-E445. 1997.
5. Rowbottom, D.G., D. Keast, and A.R. Morton. The emerging
role of glutamine as an indicator of exercise stress and overtraining.
Sports Med. 21:80-97. 1996.
6. Candow, D.G., P.D. Chilibeck, D.G. Burke, D.S. Davison,
and T. Smith-Palmer. Effect of glutamine supplementation combined
with resistance training in young adults. Eur. J. Appl. Physiol.
7. Castell LM, Poortmans JR, Newsholme EA. Does glutamine
have a role in reducing infections in athletes? Eur J Appl Physiol
Occup Physiol. 1996; 73(5): 488-90.
8. Van Gammeren, D., D. Falk, and J. Antonio. The effects
of four weeks of ribose supplementation on body composition and
exercise performance in healthy, young, male recreational body
builders: A double-blind, placebo-controlled trial. Curr. Ther.
Res. 63: 486-495. 2002.
9. Hultman, E., K. Soderlund, J.A. Timmons, G. Cederblad,
and P.L. Greenhaff. Muscle creatine loading in men. J. Appl.
Physiol. 81:232-237. 1996.
10. Oquz M, Kerem M, Bedirli A, Mentes BB, Sakrak O, Salman
B, Bostanci H. L-alanin-L-glutamine supplementation improves
the outcome after colorectal surgery for cancer. Colorectal Dis.
9(6): 515-20. 2007.
11. Fuentes-Orozco C, Anaya-Prado R, Gonzalez-Ojeda A, Arenas-Marquez
H, Cabrera-Pivaral C, Cervantes-Guevara G, Barrera-Zepeda LM.
L-alanyl-L-glutamine supplemented parenteral nutrition improves
infectious morbidity in secondary peritonitis. Clin. Nutr. 23(1):
12. Li ZH, Wang DH, Dong M. Effect of parenteral supplementation
in premature infants. Chin. Med. J. (English). 120(2): 140-144.