The Importance of Glutamate and Glutamine for the Infant Gut

Scientific evidence is clear about the importance of breastfeeding during the first six months of life, as it provides the necessary nutrients and immunological protection for the baby. Part of these benefits derives from the presence of the amino acids glutamate and glutamine—the latter also synthesized from glutamate.

The composition of human breast milk, unlike that of other mammal species, is uniquely tailored to meet all nutritional demands during the first months of life, as reported in the chapter “Glutamate in Human Milk and the Development of the Infant Gut,” written by pediatrician Manoel Baldeón and researcher Nancy Flores, published in 2021 in the book Umami and Glutamate: Chemical, Biological and Technological Aspects, edited by Prof. Félix Reyes from the State University of Campinas (UNICAMP).

Breast milk contains components that protect the infant from infections and modulate the immune response in the gut, which can be triggered by ingestion of foods and/or any substances other than breast milk (Baldeón & Flores, 2021). The milk also contains substances such as small peptides, urea, creatinine, nucleic acids, free amino acids, among other elements that influence the growth and development of the infant’s gut, formed by the non-protein nitrogen (NPN) — nitrogen not associated with proteins (Baldeón & Flores, 2021).

Among the free amino acids, glutamate—which is responsible for the umami taste—is a non-essential amino acid (i.e., produced by the body) and the most abundant in nature. Its concentration in breast milk increases after the first three months of breastfeeding, reaching approximately 50% of the total free amino acids (Zhang et al., 2013), and is responsible for physiological functions fundamental to the infant. Among these roles is that of providing energy to the epithelial cells of the intestine.

Notably, even during prolonged fasting periods—when concentrations of free amino acids in breast milk decrease—the levels of glutamate and glutamine (a non-essential amino acid synthesized from glutamate and ammonia, and also present in milk) remain stable. This suggests there is a regulatory mechanism that prioritizes their synthesis and release so that the infant continues to benefit (Li et al., 2004).

However, for all substances and nutrients in milk to function effectively, the infant’s gastrointestinal tract must be capable of receiving, digesting, and absorbing them. In other words, the infant’s gut must be prepared at birth.

To this end, during the fetal period, amniotic fluid provides nutrients, growth factors, hormones, immune cells, non-digestible oligosaccharides, among others, which promote structural and functional development of the gut.

One of the key roles of intestinal cells is to provide protection against pathogenic microorganisms by preventing their contact with the intestinal wall. This is achieved by a barrier formed by epithelial cells tightly bound to each other, called tight junctions. The barrier, along with mucus secreted into the intestinal lumen, prevents unwanted content from entering the body (Li et al., 2004; Burrin & Stoll, 2002).

In this context, some research indicates that glutamine—synthesized from glutamate or ingested through the diet—contributes both to mucus production and to maintenance of tight junctions (Li et al., 2004; Burrin & Stoll, 2002).

Furthermore, there is another immune system component located beneath the entire gastrointestinal tissue from the mouth to the anus: the GALT (gut-associated lymphoid tissue). It is within this tissue that the immune response begins and antigen processing occurs. Glutamate influences GALT, enhancing its effects (Li et al., 2004; Burrin & Stoll, 2002).

Moreover, glutamate also participates in the synthesis of glutathione, a tripeptide that transports amino acids and has antioxidant functions. In cases of intestinal stress, glutamate helps neutralize free radicals and protects against functional and structural damage (Baldeón & Flores, 2021; Li et al., 2004; Burrin & Stoll, 2002).

In summary, it becomes increasingly clear that glutamate—the principal amino acid responsible for umami taste—not only adds a special flavor to foods but is also crucial for various metabolic processes involved from development to intestinal functionality and maintenance. Consequently, it contributes significantly to well-being and health from birth into adulthood.