What is the most abundant amino acid in the human body, among alanine, valine, leucine, glutamine, and arginine?

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From the Guidelines

The most abundant amino acid in the body is glutamine, option (d). This is based on the fact that glutamine is the most abundant free amino acid in the body, as stated in the ESPEN guidelines on parenteral nutrition: intensive care 1. The guidelines highlight that glutamine participates in many metabolic processes, including protein and glucose metabolism, and is involved in cellular protection through glutathione and heat shock proteins 1. Some key points about glutamine include:

  • It is the most abundant free amino acid in the body 1
  • It is involved in many metabolic processes, including protein and glucose metabolism 1
  • It is a regulator of ammonia and acid-base balance 1
  • It is conditionally essential during times of stress, illness, or injury, as the body's demand exceeds its production capacity 1 Overall, the importance of glutamine in human physiology is well-established, and its abundance in the body makes it a critical component of various metabolic processes.

From the Research

Amino Acid Abundance in the Body

  • The most abundant amino acid in the body is glutamine, as stated in multiple studies 2, 3, 4, 5, 6.
  • Glutamine is considered the most abundant free amino acid in the body, playing a crucial role in various metabolic processes 2, 3, 4, 5, 6.

Role of Glutamine in the Body

  • Glutamine is an essential nutrient for immune cells, including lymphocytes, macrophages, and neutrophils 2.
  • It is a key metabolic substrate for rapidly dividing cells, such as those lining the gut 4.
  • Glutamine depletion can lead to impaired immune function, decreased protein synthesis, and increased mortality in critically ill patients 5.

Clinical Significance of Glutamine

  • Glutamine supplementation has been shown to improve nitrogen balance, reduce infections, and shorten hospital stays in certain patient populations 5.
  • However, the clinical benefits of glutamine supplementation are still being researched, and more studies are needed to determine its effectiveness in various situations 2, 4, 6.

Answer to the Question

  • Based on the evidence, the correct answer is (d) glutamine, as it is the most abundant amino acid in the body 2, 3, 4, 5, 6.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

[Nutritional importance of glutamine].

Arquivos de gastroenterologia, 1998

Research

Glutamine: metabolism and application in nutrition support.

Asia Pacific journal of clinical nutrition, 2004

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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