GLUTAMINE AND BRANCHED CHAIN AMINO ACIDS (BCAAs)

What are amino acids, including glutamine and branched-chain amino acids?

Amino acids are the building blocks of proteins and play essential roles in biological processes, including inflammation, glucose balance, and more, that may be involved in Long COVID. Amino acids contribute to intermediate molecules involved in energy-producing pathways. Glutamine, in particular, is used by the cell metabolism pathways and the immune system [^[1]]. Glutamine is the most abundant amino acid in the body, and it is naturally produced in the body [^[2]]. Other amino acids, such as branched-chain, are not made in the body and must be obtained from dietary sources.

BCAAs include leucine, isoleucine, and valine, which are involved in protein synthesis and glucose balance in the body. BCAAs may also directly and indirectly affect immune function [^[1]]. Both glutamine and BCAAs aid muscle recovery, especially after exercise in healthy individuals [^[3]]. 

What do glutamine and the branched-chain amino acids do in the body?

Glutamine is a source of TCA cycle intermediates that play a role in energy metabolism and may serve immune functions [^[1]]. Glutamine replenishes the intermediates used up in biological processes in immune cells such as T cells and macrophages. BCAAs can be used by immune cells and are needed for lymphocytes to create proteins and nucleotides in response to stimulation. BCAAs also serve as a source of molecules that enter the TCA cycle to support mitochondrial health [^[1]].

How can glutamine, branched-chain amino acids, and other amino acids help alleviate certain Long COVID symptoms and pathophysiology? 

Amino acids, including glutamine and BCAAs, are essential for the immune response and mechanisms involved in acute and chronic COVID-19. Especially in older adults, the changes associated with aging, such as inflammation and anabolic resistance, as well as the risk of immune dysfunction and sarcopenia, make adequate amino acid supplementation necessary. Given these considerations, researchers recommend focusing on amino acid intake in COVID-19 survivors, especially in older patients with Long COVID who might be at greater risk of malnutrition [^[1]].