Metabolic fate of dietary sialic acid and its influence on gut and oral bacteria

Abstract

In recent years, the biological functions of human milk oligosaccharides and the potential toxic effects of red meat on human health have attracted considerable attention. Sialic acid is an important carbohydrate in milk and red meat, corresponding to sialylated oligosaccharides and N-glycolylneuraminic acid (NeuGc, one type of sialic acid). Herein, we reviewed the metabolic fate of dietary sialic acid in the body and their effects on gut and oral microbes. In summary, dietary NeuAc monomer is directly excreted through urine after being assimilated through the intestines and is not utilized by the human body; in contrast, dietary NeuGc from red meat is easily utilized by the human body and can be incorporated into the brain and other organs. Sialoglycans can be partially utilized by the human body, but they do not affect the cognitive development and growth of children. Dietary sialic acid may mainly regulate the growth and metabolism of gastrointestinal microbiota and human health and development through the gut-brain axis.

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“…Sialic acid on HMOs may play a role in reducing the risk of NEC pathogenesis through complex interactions with the infant immune system, but the mechanisms are unclear ( Bode, 2018 ). One possible method is through the degradation of sialic acid by bifidobacteria due to the production of sialidases located on the nan-nag locus ( Egan et al, 2014 ; Lawson et al, 2020 ; Wu et al, 2021 ), which results in competition for nutrients with opportunistic pathogens, such as C. sakazakii and C. difficile , that can also metabolize sialic acid in the colon ( Egan et al, 2014 ).…”