Glutamine: Can It Aid Weight Loss?

Introduction

Glutamine is one of the vital amino acids among the 20 amino acids used in the protein translation process. There are two main types of glutamine present: L-glutamine, and D-glutamine. Synthesis of glutamine can be done by glutamine synthetase in plants. Glutamine synthetase is an enzyme that uses glutamate and free ammonium ions as the substrate and ATP as a source of energy. 

Multiple tissues in animals can synthesise the glutamine and dietary sources and can use this to dispose of a metabolic waste of free ammonium ions. Skeletal muscle is the most relevant glutamine-producing tissue. Glutamine helps in disposing of the nitrogenous waste by the urea cycle. This article focuses on glutamine and how it works.

Glutamine is helpful in weight loss. The supplement is taken orally (by mouth) and different doses are recommended for various problems. The glutamine supplement should always be taken after consulting healthcare practitioners. There are some side effects of this supplement; hence, precautions should be taken. 

The dietary sources rich in L-glutamine are fish, chicken, cabbage, wheat, peanuts, spinach, lentils, beans, dairy products, and corn. 

In addition to weight loss, glutamine has various other benefits, like supporting the immune system cells and helping in the detoxification of the liver of foreign substances. Furthermore, it acts as a fuel to protect the intestine and make proteins for muscle tissues. Glutamine deficiency is mainly caused by genetic disorders, however, it is rare.¹ Glutamine is also primarily linked to the intestinal health of our body.¹⁰

What is Glutamine?

The most abundant amino acid made in muscles of the body and then transferred by blood in different organ systems is known as glutamine. Glutamine performs various functions in the body as it acts as a building block for constructing proteins in the body. It is necessary for making other amino acids and glucose.¹ 

There are two types of glutamines present, namely, L-glutamine and D-glutamine. L-glutamine is mainly responsible for cell and body functions. #

The glutamine produced by our body and present in our diet is sufficient, but supplements are needed if the person has glutamine deficiency.² Glutamine supplements are primarily composed of L-glutamine and help perform gut and immune functions.^{1, 2}

Additionally, during stressful periods our bodies need more glutamine. Patients going through sickle cell disease and burns use glutamine to recover from surgery-induced injuries. Furthermore, it is also helpful in solving the complications of AIDS/HIV, diarrhoea, obesity, cystic fibrosis, and lung cancer. Glutamine also plays an important role in muscle recovery and decreased soreness after exercise and maintains the body's acid-base ratio.^{2, 3} 

How does Glutamine work?

Availability and Concentration

The availability and concentration of glutamine are dependent on the balance between how much glutamine is synthesised and taken by the organs and tissues of the body. 

The organ tissue-specific glutamine synthesis activity is followed by the lungs, liver, brain, and tissues like adipose tissues and skeletal muscles.

 Tissues like intestinal mucosa, leukocytes, and renal tubule cells consume glutamine tissues and perform high glutaminase activity. 

Certain conditions that reduce carbohydrate and amino acid absorption can create high catabolic situations, and this causes a reduction of glutamine synthesis in the muscle tissues, thus, converting the liver into a glutamine-consuming site. The performance of glutamine metabolism-regulating enzymes, namely glutamine synthetase and phosphate-dependent glutaminase can be controlled by various factors like glucocorticoids, thyroid hormones, growth hormones, and insulin.⁴ 

Synthesising Glutamine 

The enzyme glutamine synthetase present in cytosol helps synthesise the glutamine from ammonium ion glutamate by consuming ATP, and phosphate-dependent glutaminase present in the mitochondria helps in glutamine hydrolysis, which helps in converting it again into glutamate and NH4+. 

Additionally, glutamine synthetase helps produce glutamine for synthesising cytoplasmic proteins and nucleotides, and phosphate-dependent glutaminase helps catalyse the glutamine conversion to glutamate, which is vital in the Krebs cycle because it acts as an energy source for metabolic intermediates in that cycle. 

Glutamine synthesis is dependent on the availability of glutamine synthetase because glutamate is produced from 2-oxoglutarate NH4 by the action of glutamate dehydrogenase. It is also obtained from the catabolism of leucine. 

The activities performed by glutamine synthetase and phosphate-dependent glutaminase affect the glutamine tissues and blood concentrations. In severe conditions like cancer, sepsis, various infections and surgeries, traumas, and intense and prolonged physical exercise, the human body cannot meet the catabolic states of endogenous glutamine synthesis. 

Glutamine Deficiency 

When the body is going through a deficiency condition, there is an increase in phosphate-dependent glutaminase action and inhibition of glutamine synthetase action because glutamine acts as a conditionally essential amino acid. Although the plasma glutamine concentration is decreased from 500-800μmol/L to 300-400μmol/L, there is still no influence on the proliferation and function of immune cells - the high tissue catabolism results in the reduction of glutamine stock in muscle and liver. The amino acid helps provide the nitrogen atoms to synthesise purines, pyrimidines, and amino sugars; therefore, the low glutamine concentration in human tissues affects the whole body. Immunosuppression will occur if the high glutamine degradation in these tissues continues because then many metabolic pathways and mechanisms which depend on glutamine availability will be affected.⁴

The gut microbiome is affected by L-glutamine since the gut microbiota plays a significant role in an individual's health, resulting in gut inflammation and leading to obesity.⁵

Does Glutamine aid weight loss?

Glutamine can be used by people who would like to reduce body fat whilst retaining muscle mass. Glutamine helps regulate the blood sugar level and promotes muscle development by preventing muscle breakdown. Therefore, it is useful when a bodybuilder is on a diet, and hence, they supplement their diet with glutamine. Additionally, glutamine protects the immune system and plays an essential role in responding to stressful exercise; therefore, it indirectly supports fat loss. 

When an individual is active while exercising, lactic acid is produced in the muscles, which leads to the production of soreness and a sensation of burning in worked muscles after the workout sessions. It helps counteract this cellular activity and prevent the accumulation of ammonia in the blood. 

This happens when the water is drawn into the tissues to dilute and flush out the ammonia and the acid present in the blood. 

Stressful exercise can cause a high secretion of the hormone cortisol, which our body uses to prepare us to fight against stressful conditions. 

When a human body is in a stressful situation, a natural defence mechanism works by releasing cortisol which helps in muscle loss and weight gain. Therefore, glutamine works to respond to the effects of stressful conditions and the production of cortisol, resulting in reduced storage of fat in the body. 

When an individual is controlling the calorie intake, weight is lost because the fat is burnt due to reduced fat storage in the body, resulting from regular exercise and increased cellular activity.⁶ The high HGH production and metabolic rates in overweight people result in fat burning. Hence, weight loss is observed. Glutamine supplements can increase lean body mass and reduce the circumference of the abdomen. Appetite can be controlled by L-glutamine.⁷

How to take Glutamine 

An oral dosage of glutamine is advised for adults for up to 12 months. Manufacturers usually use 20-30 grams per day as the average recommended glutamine dosage. 

To maintain the high plasma levels, 10gm glutamine supplements should be taken thrice a day. While an individual is under training period, 10 grams are taken before training, and 10 grams are taken after the training to boost the recovery effects, leaky gut, and fight fatigue. 

Glutamine supplement is consumed after every 6 hours on non-training days.⁸ 1-3 grams of supplements should be taken per day to maintain general health. 

When a person is suffering from HIV/AIDS and goes through involuntary weight loss,14-40 grams of supplements are advised every day. During the patient's critical illness, a liquid diet of 0.2-0.6g/kg of body weight every day or 20 grams every day is recommended for the individual. In the burnt condition, it is advised to take 0.35- 0.5g/kg of body weight every day or 4.3 grams every 4 hours. 

For an individual of 5 years or above going through sickle cell disease, it is recommended to take 5-15 grams twice a day for 48 weeks.⁹ The person may face symptoms like bloating, nausea, dizziness, heartburn, and stomach pain due to side effects if the supplement is taken in more than the recommended quantity. It is safe to take glutamine supplements for the short-term, but research is still needed to observe the long-term effects.¹⁰

Summary 

Glutamine helps lose weight in direct and indirect ways related to metabolic pathways. Gut microbiota plays an essential role in weight management as it protects the body against the inflammation which can cause obesity. L-glutamine supplements help alter the gut microbiome's composition, hence losing weight and improving insulin sensitivity.¹⁰ 

There are recommended dosages of glutamine supplements given to the patients by healthcare practitioners. However, excess consumption can be harmful. Some precautions and warnings are advised for breastfeeding and pregnant women, children, patients with liver disease, bipolar disorder, seizures, and people having monosodium glutamate sensitivity.¹