Athletes and bodybuilders are always looking for a training edge. For athletes, it’s a performance edge. For bodybuilders, it’s a muscle building advantage. Some bodybuilders, amateur and professional, even resort to taking supplements in hopes of boosting muscle growth. One such supplement is glutamine, a supplement available with other amino acids and in isolated form. Is there any scientific evidence that glutamine can boost muscle growth?
What is Glutamine?
Glutamine is a non-essential amino acid. Since it’s non-essential, your body can make this amino acid and doesn’t have an absolute requirement for it from diet. However, it is possible for the body’s need for glutamine to exceed the amount the body can make. In most cases, a healthy human can make enough glutamine to support health. Where glutamine needs may not be met is in humans that are injured, ill, or under a great deal of stress. Studies show that giving glutamine to patients after surgery helps preserve muscle mass. We also know that exercise places stress on the body and that raises the question of whether people who work out vigorously need more glutamine and whether glutamine can improve exercise performance or boost muscle growth.
Can Supplementing With Glutamine Enhance Muscle Hypertrophy?
If you’re trying to build muscle, you might wonder whether taking a glutamine supplement or increasing the amount of glutamine in your diet can help you build muscle or even make you stronger. In one study, researchers asked 31 men and women who already strength trained to take part in six weeks of resistance training. One group received a glutamine supplement while the other took a placebo. The dose they got, 0.9 grams of glutamine per kilogram of body weight, was a relatively high amount. Despite the generous dose of glutamine, strength, and muscle gains were similar in the two groups. The placebo group gained just as much strength and mass as the group that got the placebo. The glutamine supplement didn’t seem to offer a strength or hypertrophy advantage.
Other evidence supports these findings. A 2018 analysis of five studies looking at the impact of glutamine on muscle growth also found that supplementation offered no benefits with regard to muscle gains. This doesn’t mean that glutamine doesn’t play a role in muscle growth, but it’s likely that most people get enough from their body’s ability to synthesize it and from diet. Beyond a certain threshold, more doesn’t boost muscle protein synthesis. That might be a disappointment to bodybuilders who spend money on glutamine supplements!
Supplementing With Glutamine Has an Anti-Catabolic Effect
Where glutamine may be beneficial is for athletes, particularly endurance athletes, who train intensely for long periods of time. Prolonged endurance training places excessive stress on the body and may boost the body’s glutamine needs. It’s possible that the body may not be able to keep up with the demands when training is excessive. If so, it could lead to a catabolic state and muscle loss.
Another source of stress on the body is calorie restriction. A 2003 study looked at whether supplementing with glutamine could prevent or reduce the loss of lean body mass during short-term calorie restriction. Unfortunately, glutamine supplementation didn’t preserve lean body mass in athletes who dieted over a 12-day period. Another strike for glutamine.
But Supplementing With Glutamine May Still Have Benefits
Supplementing with glutamine doesn’t seem to boost muscle hypertrophy, but it may still have benefits. Some research suggests that supplemental glutamine can boost muscle recovery after strength training. One small study involving 15 men found that supplementing with glutamine (0.3 grams per kilogram of body weight) after a strength-training workout reduced post-workout muscle soreness more than a placebo. The guys who supplemented with glutamine also recovered their strength faster. However, some studies that used lower doses found no benefit.
Another way glutamine may offer benefits is through an impact on the immune system. Cells that participate in the body’s immune response and protect against infection need adequate amounts of glutamine to function properly. Research shows glutamine is particularly important for healthy functioning of immune cells in the gut. In fact, more than 70% of your immune system is in your intestinal tract. After a tough workout, glutamine levels may fall transiently, this could cripple the immune cells that protect against viral and bacterial infections.
Do the immune benefits of glutamine hold up to science? Some studies suggest that supplementing with glutamine may reduce the risk of infection in people who engage in exhaustive exercise. Unfortunately, there are so many variables to consider, the nature of the exercise, how strenuous it is, the age and health of the participants, and how much protein they already get in their diet. It makes sense that people who eat a relatively low protein diet and do exhaustive exercise might benefit from glutamine supplementation more than someone who eats a diet already high in protein.
Where glutamine may exert its greatest immune benefits is on the intestinal tract. Remember, 70% of immune cells are in the gut. There’s some evidence that prolonged or intense exercise transiently damages the ultra-thin lining of the gut and allows proteins to leak from the gut into the bloodstream. When proteins leak out, it can elicit an immune response that leads to inflammation, a so-called leaky gut. Glutamine supplementation may reduce the risk of this happening. Glutamine is also a component of glutathione, the master antioxidant inside cells. Glutathione is a key component for keeping cells healthy and for protecting against oxidative damage.
The Bottom Line
It’s unlikely that supplementing with glutamine will boost strength or hypertrophy gains if you’re healthy. However, there is some evidence that it might preserve immune health during long periods of strenuous exercise. In other words, if you’re training for a marathon, there may be some benefit to adding more glutamine to your diet. But, overall, it’s best to focus on eating a nutrient-rich diet that contains enough calories and protein rather than supplementing with isolated amino acids, like glutamine.
References:
· J Nutr. 2008 Oct;138(10):2045S-2049S.
· J Sports Sci Med. 2003 Dec; 2(4): 163–168.
· International Council on Amino Acid Science. “Glutamine and Immune System Support”
· J Appl Physiol (1985). 2016 Mar 15;120(6):692-701.
· Eur J Appl Physiol Occup Physiol. 1996;73(5):488-90.
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