Nutrition, immunosenescence and infectious disease: An overview of the scientific evidence on micronutrients and on modulation of the gut microbiota

Authors: CALDER, PHILIP - University Of Southampton; ORTEGA, EDWIN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; MEYDANI, SIMIN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; Adkins, Yuriko; Stephensen, Charles; THOMPSON, BRICE - University Of Washington; ZWICKEY, HEATHER - University Of Portland

Submitted to: Advances in Nutrition
Publication Type: Review Article
Publication Acceptance Date: 5/4/2022
Publication Date: 10/3/2022
Citation: Calder, P.C., Ortega, E.F., Meydani, S.N., Adkins, Y.C., Stephensen, C.B., Thompson, B., Zwickey, H. 2022. Nutrition, immunosenescence and infectious disease: An overview of the scientific evidence on micronutrients and on modulation of the gut microbiota. Advances in Nutrition. 13(5):S1-S26. https://doi.org/10.1093/advances/nmac052.
DOI: https://doi.org/10.1093/advances/nmac052

Interpretive Summary: People are increasingly interested in understanding how to optimize their health and strengthen their immune system with nutrition especially as a result of the current COVID-19 pandemic. Several factors can depress the immune system, including older age, as the body becomes less efficient in making immune cells that are required to fight off an infection. Collectively, this condition termed “immunosensecence”, can lead to a pro-inflammatory state called inflamm-aging. This coupled with poor diet and malnutrition, which can occur at any age, can increase the risk for Upper Respiratory Tract Infections (URTIs) and other infectious diseases. A review of the current scientific literature shows that several bioactive ingredients including prebiotics, probiotics, synbiotics and others have promising immune health benefits. Bioactives, are complex ingredients with multiple mechanisms of action (MOAs), however, their effects are dependent upon the environment of the user. Therefore, the purpose of this session is to provide an overview of immunosensecence and the function of micronutrients in healthy immunity. A discussion on bioactive ingredients and the scientific evidence behind them will also be covered. This session will conclude with a discussion on the role of nutritional ingredients in infectious disease and will conclude by highlighting emerging areas for future research.

Technical Abstract: The immune system is key to host defence against pathogenic organisms. Aging is associated with changes in the immune system, with a decline in protective components (immunosenescence), increasing susceptibility to infectious disease, and a chronic elevation in low grade inflammation (inflammaging), increasing risk of multiple non-communicable diseases. Nutrition is a determinant of immune cell function and of the gut microbiota. In turn, the gut microbiota shapes and controls the immune and inflammatory responses. Many older people show changes in the gut microbiota. Age-related changes in immune competence, low grade inflammation and gut dysbiosis may be interlinked and may relate, at least in part, to age-related changes in nutrition. A number of micronutrients (vitamins C, D and E and zinc and selenium) play roles in supporting the function of many immune cell types. Trials providing these micronutrients as individual supplements can reverse immune deficits in older people and/or in those with insufficient intakes. There is inconsistent evidence that this will reduce risk or severity of infections including respiratory infections. Probiotic, prebiotic or synbiotic strategies that modulate the gut microbiota, especially by promoting the colonization of lactobacilli and bifidobacteria, have been demonstrated to modulate some immune and inflammatory biomarkers in older people and in some cases to reduce risk and severity of gastrointestinal and respiratory infections, although again the evidence is inconsistent. Further research with well-designed and well-powered trials in at-risk older populations is required to be more certain about the role of micronutrients and of strategies that modify the gut microbiota-host relationship in protecting against infection, especially respiratory infection.