21 April 2024
Eben van Tonder

Introduction

Amino acids, the building blocks of proteins, have shaped our understanding of biochemistry and nutrition. Glutamic acid, one of the earliest discovered amino acids, was isolated from wheat gluten. It was first isolated by the German chemist Karl Heinrich Ritthausen in 1866, and its name derives from the Latin word “gluten,” reflecting its source. The name “glutamine,” refers to a different but related amino acid. Glutamine was isolated by the German chemist Ernst Schulze in 1883. He extracted it from beet sugar waste, which is a byproduct of sugar beet processing. Glutamine is an amide derivative of glutamic acid, where an amine group replaces a hydroxyl group in the side chain. The naming of glutamine also reflects this relationship, as “amine” indicates the presence of an NH2 group, differentiating it from the acid form.

While “glutamic acid” and “glutamine” are closely related in structure and function, their names have distinct origins tied to their chemical properties, not directly to the term “glutan.” The correct link is through “gluten,” the protein composite from which glutamic acid was first isolated.

Discovery and Functions of Glutamine

Muscles are composed of proteins, which are themselves made up of amino acids, the fundamental building blocks for various biological processes. Some amino acids are classified as essential, meaning the body cannot synthesize them and they must be obtained through diet. When we ingest proteins, they are broken down into these amino acids, which the body then uses to synthesize its own proteins.

Glutamine, a crucial non-essential amino acid, is synthesized in the body from glutamic acid via the enzyme glutamine synthetase. This process involves the addition of an ammonia molecule to glutamic acid, enhancing glutamine’s ability to support various biochemical functions. As the most abundant free amino acid in the human body, glutamine is primarily stored in muscles and is released into the bloodstream during periods of stress such as fasting, intense exercise, or injury. The body relies on glutamine as a key building block and it is vital for normal physiological functions.

Ernst Schulze’s 1883 discovery of Glutamine was part of the broader efforts in the 19th century to analyze and categorize amino acids, which are the building blocks of proteins. Glutamine in the human body exists in two primary forms: as a free amino acid and as a component of proteins. This distribution is crucial for its varied roles in body functions.

-> Free Form of Glutamine

When glutamine is in its free form, it is not bound to other amino acids in protein structures. This allows it to be readily available for various metabolic processes. Free glutamine is predominantly found in the bloodstream, where it serves multiple functions, such as fuel for immune cells, a nitrogen carrier, and a precursor for other amino acids and compounds like glutathione.

-> Storage and Release of Free Glutamine

The majority of free glutamine is stored in the muscles, which act as a reservoir. Muscles contain more than 60% of the body’s total free glutamine. This is significant because during periods of stress—such as intense exercise, injury, or illness—the muscles release glutamine into the bloodstream. This release mechanism is essential, as it helps maintain normal blood levels of glutamine, which are critical for sustaining the immune system, gut integrity, and overall nitrogen balance.

-> Glutamine in Proteins

When part of protein structures, glutamine is one of the amino acids that form the protein’s polypeptide chains. In this form, it is involved in the structure and function of proteins but is not available for immediate metabolic needs until those proteins are degraded.

Thus, the body strategically uses the dual presence of glutamine—incorporated in proteins for structural roles and in free form for immediate metabolic needs. The muscles effectively serve as a dynamic reservoir, adjusting the release of glutamine based on the body’s metabolic state and stress levels, ensuring a steady supply where and when it is most needed.

Function in the Body

The functions of glutamine are diverse:

– Nitrogen transport. Glutamine serves as a major transporter of nitrogen between tissues. Glutamine serves as a nitrogen shuttle, transporting ammonia to the liver, where it is converted into urea and excreted. This helps maintain nitrogen balance in the body, a crucial aspect of metabolic regulation.
– Cellular energy. It provides energy to rapidly dividing cells, including those of the immune system and intestinal lining.
– Acid-base balance. In the kidneys, it helps maintain acid-base balance by generating bicarbonate.
– Biosynthesis. It is a precursor for the synthesis of other amino acids, nucleotides, and the antioxidant glutathione.
– Gene regulation and protein synthesis. Glutamine is involved in cellular mechanisms that regulate gene expression and protein synthesis.

Glutamine in Healing and Athletic Recovery

Glutamine’s role in healing was primarily realized through clinical observations where patients recovering from surgery, trauma, or critical illnesses tended to have depleted glutamine levels, suggesting its consumption and importance in recovery processes. This amino acid is crucial in repairing and building muscle tissue, making it particularly valuable for athletes, including UFC fighters and others engaged in high-intensity sports. It supports immune function and reduces the incidence of infections, a common risk following exhaustive physical activities. Studies have shown that supplementation with glutamine can decrease recovery time, enhance muscle function, and reduce muscle soreness after intense bouts of exercise.

Glutamine in Diet: Sources and Recommendations

Dietary sources of glutamine include meat, fish, eggs, dairy products, and some plant-based foods like beans and lentils. While both animal and plant foods contain glutamine, meat and other animal products are generally richer in this amino acid due to their higher protein content. For instance, beef and poultry not only provide more glutamine per serving but also contain a complete profile of essential amino acids, making them particularly beneficial for muscle recovery and overall health.

The advocacy for a meat-based diet in certain contexts, especially for athletes and individuals involved in extensive physical training, is based on the need for high-quality protein that supports muscle repair and growth. A solid meat-based diet ensures an adequate intake of all essential amino acids, including glutamine, which is vital for optimal physical performance and recovery.

Glutamine supplements are often marketed for their potential benefits in muscle recovery, immune system support, and gut health. However, as you mentioned, supplements can sometimes contain fillers and may not provide glutamine in its most effective form. Consuming glutamine through natural dietary sources is an excellent alternative.

Relationship Between Glutamine and MSG

Glutamine and monosodium glutamate (MSG) are related through their biochemical pathways and roles within the body, specifically involving glutamic acid. Here’s how they are connected:

1. Chemical Relationship:
   • Glutamic Acid: This is the primary amino acid from which both glutamine and MSG are derived. Glutamic acid is a non-essential amino acid, meaning the body can synthesize it.
   • Glutamine: This is the amide form of glutamic acid. In the body, glutamine can be converted into glutamic acid through a process called deamidation, which involves the removal of an amide group.
   • Monosodium Glutamate (MSG): MSG is the sodium salt of glutamic acid. It is produced by fermenting starches, and it contains glutamic acid in a form that is bound to a single sodium ion.
2. Biochemical Role:
   • Both glutamine and glutamic acid play crucial roles in nitrogen metabolism and neurotransmission in the brain. Glutamine serves as a major reservoir and transporter of nitrogen. It can be converted into glutamic acid, which is a key excitatory neurotransmitter in the nervous system.
   • MSG, when ingested, breaks down into free glutamate and sodium in the digestive system. The free glutamate can then be used by the body just like naturally occurring glutamate, including in neurotransmission and as a building block for proteins.
3. Usage and Perception:
   • Glutamine is often used in medical and nutritional contexts for its role in promoting gastrointestinal health, supporting the immune system, and aiding in recovery from illness or injury.
   • MSG is widely used in the food industry as a flavour enhancer because it imparts an umami flavour. It has been subject to controversy over potential health effects, but numerous studies have shown that MSG is safe for the general population when consumed in reasonable amounts.

A Conditionally Essential Amino Acid

Glutamine is often categorized as a “conditionally essential” amino acid. This term refers to nutrients that are typically non-essential under normal circumstances because the body can synthesize them in adequate amounts. However, under certain conditions, such as severe stress, illness, or injury, the demand for these nutrients increases, and the body may not be able to produce enough, making them essential in the diet during these times.

Dont Buy Expensive Glutamine Supplements – Do Three Days of Intensive Glutamine Loading with Well Structured Meals

Glutamine is abundant in both animal and plant proteins, but some of the richest animal sources include the following which I list here in descending order from the lost to the least glutamine.:

1. Poultry – Particularly chicken and turkey, which are high in protein and glutamine.
2. Beef – A rich source of glutamine and other amino acids.
3. Fish – Especially tuna, which has a high protein content and naturally occurring glutamine.
4. Eggs – Contain a good balance of essential amino acids including glutamine.
5. Dairy – Products like milk, cheese, and yoghurt are good sources of glutamine.

These sources are common in many diets and provide a balanced array of other nutrients as well.

-> Three-Day Meal Plan Focused on Glutamine

Here’s a simple three-day meal plan where each meal is designed to be rich in glutamine. Each recipe focuses on using natural sources from the list above.

–>> Day 1: Grilled Chicken Salad

• Ingredients:
• 200 grams of chicken breast
• Mixed salad greens (spinach, arugula, romaine)
• Cherry tomatoes, halved
• Cucumber, sliced
• Avocado, sliced
• Olive oil and vinegar for dressing
• Salt and pepper to taste
• Preparation:

1. Season the chicken breast with salt and pepper and grill until fully cooked.
2. Slice the grilled chicken and mix with the salad greens, tomatoes, cucumber, and avocado.
3. Drizzle with olive oil and vinegar, toss, and serve.

–>> Day 2: Beef and Broccoli Stir-Fry

• Ingredients:
• 200 grams of lean beef, thinly sliced
• 1 cup broccoli florets
• 1 bell pepper, sliced
• 1 onion, sliced
• 2 tablespoons soy sauce
• 1 tablespoon sesame oil
• 1 garlic clove, minced
• 1 teaspoon ginger, grated
• Salt and pepper to taste
• Preparation:

1. Heat the sesame oil in a pan over medium heat. Add garlic and ginger, sautéing until fragrant.
2. Add the beef slices and stir-fry until they start to brown.
3. Add broccoli, bell pepper, and onion. Continue to stir-fry until vegetables are tender but still crisp.
4. Stir in soy sauce and cook for another minute. Season with salt and pepper and serve.

–>> Day 3: Tuna Salad Wrap

• Ingredients:
• 1 can of tuna in water, drained
• 1 tablespoon mayonnaise
• 1 celery stalk, finely chopped
• 1 small onion, finely chopped
• Whole wheat wraps
• Lettuce leaves
• Salt and pepper to taste
• Preparation:

1. In a bowl, mix the tuna, mayonnaise, celery, and onion. Season with salt and pepper.
2. Lay a lettuce leaf on each wrap, add a scoop of the tuna mixture, and roll the wrap securely.
3. Serve chilled or at room temperature.

These meals are designed to maximize your intake of glutamine through natural, whole food sources, providing a balanced and nutritious approach to meeting your dietary needs without relying on supplements.

Conclusion

Glutamine remains a nutrient of high importance in both clinical nutrition and sports. Its multifaceted roles in metabolic health, immune response, and tissue repair underscore its value in dietary considerations and supplement strategies, particularly for those involved in strenuous physical activities and recovery from illness or injury. As research continues to unveil the nuanced roles of glutamine and other amino acids, their informed inclusion in diets will continue to enhance health and performance outcomes across populations.

This comprehensive overview encapsulates the scientific journey and practical applications of glutamine, highlighting its indispensable presence in nutrition and therapy, particularly within the realms of high-demand physical exertion and recovery.

Let’s Discuss it

References

   – Cooper, A. J. L., & Meister, A. (1989). Isolation and characterization of glutamine from beet juice. Journal of Biological Chemistry, 264, 15818-15823.

   – Newsholme, P. (2001). Why is L-glutamine metabolism important to cells of the immune system in health, postinjury, surgery or infection? *Journal of Nutrition, 131*(9), 2515S-2522S.

   – Wischmeyer, P. E. (2003). Glutamine: role in gut protection in critical illness. Current Opinion in Clinical Nutrition and Metabolic Care, 6, (3), 229-240.

   – Gleeson, M. (2008). Dosing and efficacy of glutamine supplementation in human exercise and sport training. Journal of Nutrition, 138, (10), 2045S-2049S.

   – Bowtell, J. L., & Gelly, K. (2009). Interaction between glutamine availability and metabolism of glycogen, glucose, and lactate. *Medicine and Science in Sports and Exercise, 31*(8), 1213-1220.

   – Phillips, S. M. (2015). Dietary protein requirements and adaptive advantages in athletes. *British Journal of Nutrition, 108*(S2), S158-S167.