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Maximizing and Maintaining Muscle with L-Glutamine


nutrition articles

March 2015

Maximizing and Maintaining Muscle with L-Glutamine

Written By Nicole Crane, B.S., NTP

The muscles all over your body are essential to overall health and wellness. Opening your eyes, smiling, sitting, walking, and even breathing, all require muscles. We need cardiac muscle to keep our heart beating, we need skeletal muscle to move our bodies, and we need smooth muscle to maintain healthy organs that function well. These three types of muscle, cardiac (heart), skeletal muscle, and smooth muscle, each play an important role in overall wellness. Cardiac muscle is found only in the heart, while skeletal muscles attach to the bones and allow us to move. Smooth muscle lines the organs, like our digestive tract, bladder and other hollow organs. The cardiac and smooth muscles are under the control of the body and move involuntarily, while skeletal muscles are controlled voluntarily. There are over 650 different muscles in the human body – men are 42% muscle, while women are 36% muscle, on average, at a healthy weight.1

How to Build and Maintain Muscle

Building and maintaining muscle is one of the best ways to ensure an active, healthy lifestyle without aches, pains and injuries. Healthy muscles support healthy metabolism, as the muscles are more metabolically active than body fat. On average, a pound of muscle will burn three times as many calories as a pound of body fat.2 Greater muscle mass increases our basal metabolic rate (i.e., faster calorie burning). Increased metabolism supports healthy weight and an optimal rate of aging. Healthy muscles give the body strength and can prevent slips and falls. Every year, one-third to one-half of the population age 65 and over experience falls, and about half of elderly people who suffer from a fall do so repeatedly. Falls cause approximately 300,000 hip fractures annually.3 When the muscles are strong enough to support the weight of the body, the likelihood of falls is significantly decreased. Not only do strong muscles keep bones and joints strong by exerting more force on them, muscles provide the body with greater balance, agility and strength. It’s important to maintain as much muscle as possible, especially throughout the aging process. Beginning at about age 30, 0.5% of our muscle mass is lost per year, and the rate of muscle loss can accelerate when you reach age 60-70. By age 65, approximately 30% of muscle mass is gone, especially in those who are inactive.4 Luckily, there is a very special amino acid (the building blocks of protein) called L-Glutamine that nourishes the muscles and can even help to build and repair muscles, at any age!5,6

How does Glutamine work in the body?

Glutamine is considered a non-essential amino acid, meaning that under certain circumstances it becomes conditionally essential. For example, if the body cannot make enough on its own, body stores become depleted and it becomes necessary to obtain glutamine from food or supplements. Glutamine is classified as non-essential because the body can make it in sufficient amounts under optimal conditions, and thus does not need to get it from food. However, this does not mean it is not essential for health. It is the most prevalent amino acid in the body, making up 20% of the body overall and 60% of skeletal muscle.


Glutamine is an amazing source of energy for all the muscles in the body. It nourishes and serves as fuel for both the skeletal and smooth muscles. About 55-65% of free form amino acids in skeletal muscle are made of glutamine. Glutamine's unique structure, containing two nitrogen side chains, consists of 19% nitrogen. This makes it the primary transporter of nitrogen into the muscle cells. Glutamine is thought to contribute to a positive nitrogen balance, which fosters a cellular environment that is conducive to muscle building.7 Glutamine drives a hormonal pathway that fosters the building of muscle and slows the rate at which muscle is broken down, especially when the body is stressed, injured, infected or energy-depleted.8 Since glutamine is muscle fuel, it serves as an essential source of energy while the body is in motion and the muscles are most active. This makes it great for those who exercise often, and for those who want to maximize muscle building.9

Anabolic State

Furthermore, glutamine supports the body's ability to maintain an anabolic state where growth and repair take place, especially when under physical or mental stress. Glutamine also helps muscles heal much more efficiently, whether damaged from injury or surgery. Glutamine helps to replenish glycogen stores10 – glycogen is how the body stores carbohydrates in the muscles and the liver. Glycogen loading is why athletes will consume carb-dense meals before competition or intense exercise. The body has the ability to store about 2,000 calories’ worth of glycogen in muscles. Glutamine helps reach maximum glycogen stores, which supports optimal athletic performance and more efficient exercise recovery.11

Growth horomones

Glutamine’s impact on metabolic rate goes beyond its role in supporting muscle growth and repair. Glutamine also increases the production of growth hormone, which is produced by the pituitary gland and has many complex functions that encourage the body to burn fat for energy. Healthy levels of growth hormone also support repair and regeneration of all body tissues, including muscles. Growth Hormone stimulates the body cells to grow in size and increases healthy levels of cell division. In addition, it enhances the movement of amino acids through cell membranes and increases the rate at which these cells convert these molecules into proteins. Growth hormone helps the body to exercise with more efficiency and aids in the oxygenation of the body. It also stimulates growth and repair of collagen, cartilage and muscle, all of which decline with age. Growth Hormone helps the body burn fat for energy and maintains a healthy metabolic rate.12 Levels of this powerful hormone can be directly linked to how optimally the body is aging. Youthful levels of growth hormone support overall health. In one study, scientists administered 2,000 mg of glutamine dissolved in a beverage to nine healthy adult subjects. Eight out of the nine subjects responded to the oral glutamine intake, with a four-fold increase in growth hormone output.13

Digestive Health

Glutamine is also wonderful for people who have intestinal dysfunction, like diarrhea, food intolerances and inflammatory disorders of the digestive tract.14 Glutamine helps to repair damage to the gastrointestinal caused by poor diet, stress, overgrowth of bad bacteria, medications and other factors, a condition known as intestinal hyper-permeability or leaky gut syndrome. The small intestine cells require glutamine to produce energy, making it quite effective for supporting the healthy function of cells in the digestive tract. Glutamine also helps to support the structural integrity of GI tract15, as it helps to regenerate intestinal mucosa and repair gap junctions16 (the spaces between intestinal cells). Glutamine supports healthy microvilli, the part of the lining of the GI tract where we absorb nutrients and release digestive enzymes. Healthy microvilli are an essential aspect of digestive wellness. The intestinal tract is made of both a muscular layer and a mucosa layer. Glutamine supports the structural integrity of the entire intestinal tract by helping to regenerate intestinal mucosa and repairing the muscle of the gut.17 Remember, the basic function of an amino acid is to maintain proper growth and repair of all cells. Glutamine is special, as it also serves as a major source of energy for the intestinal tract. The GI tract needs a lot of energy – in fact, it consumes 40-50% of the glutamine in the body.18 When the gut cells have enough energy, gap junctions regain strength, leaky gut membranes start to heal, the intestinal barrier is strengthened and the amount of toxins that enter the body are reduced. The body’s exposure to gut microbes is normalized, the microvilli are tall and healthy and the gut muscles can perform peristalsis (contractions) for healthy elimination and optimal functioning.


Glutamine becomes conditionally essential during trauma and other catabolic stress, like injuries and falls, infections, wounds and burns or even intense exercise like marathon training.19 Under these conditions, muscle stores of glutamine become rapidly diminished and Glutamine helps speed healing and reduces inflammatory responses. In a state of stress, the body rapidly drains its stores of glutamine, becoming much more vulnerable to slowed healing time, increased inflammation and infection. Glutamine directly helps to regulate and turn off inflammation and aid in healing, which further normalizes the inflammatory response and serves as an energy source for immune cells.20 Glutamine offers great benefits for modulating immune function, especially when the body is experiencing trauma or infection, by energizing and proliferating white blood cells like lymphocytes and macrophages.21

The benefits of Glutamine seem endless. Glutamine is also a precursor to the body’s master antioxidant and liver detoxifier, Glutathione.22 As we get older, glutathione levels decline. This decline is associated with accelerated aging and increased inflammatory response. Glutamine has been shown to effectively rebuild and maintain youthful levels of glutathione, the primary driver of detoxification pathways in the liver, brain, lungs and kidneys. Glutamine and glutathione support the optimal functioning of all the body’s organs and keep us young at the cellular level.

While diet has the biggest impact on blood sugar regulation and dis-regulation, muscle mass also plays a crucial role in maintaining blood sugar balance. When there is less muscle, it becomes more difficult for the body to regulate blood sugar balance. Muscle mass influences overall metabolic rate and how many calories are burned in a state of rest. Muscles act like a sponge for glucose (sugar). Studies show that after a meal, glutamine supplementation increased circulating levels of insulin among those with poor blood sugar control.23 When fasting, glutamine also stimulated glucagon secretion in those with normal and poor blood sugar control. Glucagon is the hormone that allows the body to burn fat for energy in between meals. Glutamine aids in blood sugar balance, and with healthy glucose control, the body as a whole can maintain health.

Glutamine is a major key factor in supporting the body’s overall health, wellness and proper functioning. It supports the body in so many ways that help us heal from poor lifestyle choices, such as processed-food diets, drugs and alcohol use, overuse of medications, sedentary lifestyles, and stress. By energizing the intestinal cells, the body can absorb more nutrients, allowing less toxins in the system and ultimately slowing the aging process. Glutamine also energizes and helps build muscle, which in turn improves basal metabolic rate and supports the body whether it’s in motion or resting. Glutamine increases muscle strength, providing the body with increased balance, agility and mobility.


  2. Wang, Z., Heshka, S., Zhang, K., Boozer, C.N., & Heymsfield, S.B. (2001). Resting energy expenditure: systematic organization and critique of prediction methods. Obesity Research, 9, 331-336
  7. Hammarqvist, F. et al., 1990. Alanyl-glutamine Counteracts the Depletion of Free Glutamine and the Postoperative Decline in Protein Synthesis in Skeletal Muscle : Ann. Surg. 212: 637-644.
  9. Agostini F, Giolo G. Effect of physical activity on glutamine metabolism. Curr Opin Clin Nutr Metab Care. 2010; 13(1):58-64.
  16. Unno N, Fink MP. Intestinal epithelial hyperpermeability. Mechanisms and relevance to disease. Gastroenterol Clin North Am. 1998 Jun;27(2):289-307.
  23. Prada, P.O., Hirabara, S.M., de Souza, C.T., Schenka, A.A., Zecchin,H.G., Vassallo, J., Velloso, L.A., Carneiro, E., Carvalheira, J.B., Curi, R. & Saad, M.J. (2007) L-glutamine supplementation induces insulin resistance in adipose tissue and improves insulin signalling in liver and muscle with diet-induced obesity,Diabetologia, Volume 50, issue 9, (pp. 149-159)


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