Understanding the role of milk in regulating human homeostasis in the context of the COVID-19 global pandemic

Abstract

Although data from clinical observation have directly shown that children aged 0-14 years are less susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than those who are between 15 and 64 years old, due to a lack of biological evidence of differences in cell entry receptors between age groups, it remains debatable whether children are actually less susceptible than adults. To date, studies on COVID-19 have consistently shown that pediatric patients generally have relatively milder cytokine release syndrome and lower mortality rates than adults. Interestingly, similar phenomena of relatively mild symptoms in children have been observed in previous outbreaks of coronaviruses, including SARS-CoV and MERS-CoV. In fact, in the early stage of life, there are many mechanisms that spontaneously regulate excessive inflammatory responses. Milk, as the main food of infants, not only provides necessary energy and nutrients but also plays an important role in regulating homeostasis related to the immune system, gut microecology and nutrition balance. This review discusses some roles of milk in regulating human homeostasis, especially in the disease states. These clues provide new insight and references for personal care at home and/or in the hospital during the global COVID-19 pandemic.

Fig. 1

Homeostasis orchestrated by milk in COVID-19 patients. Phenomena: 1, Mild symptoms in children were observed in outbreaks of SARS-CoV-2; 2, cytokine storms correlate positively with COVID-19 severity; View points: children regulate homeostasis in the disease state through a series of mechanisms, which is conducive to alleviation of the disease; 2. milk plays a very important role in the maintenance of homeostasis. A: Immune homeostasis: Milk and its nutrients can regulate excessive inflammation. For example, myeloid cells can differentiate into MDSCs and attenuate excessive inflammation by using LRP-2 to sense lactoferrin from milk. B: Intestinal homeostasis: Aging, anxiety, medication and fever disrupt homeostasis in the gut. Imbalance of the intestinal microbiota can aggravate the development of disease by reducing food digestibility, producing harmful metabolites and inflammatory cytokines. Milk is rich in prebiotics, which can reverse the imbalance of gut microbiota and promote intestinal health. C: Nutritional homeostasis: Fever symptoms can cause loss of appetite and digestive enzyme activity, leading to malnutrition during illness. At this time, a large number of immune cells proliferate, and the demand for nutrition increases. Milk can provide essential nutrients for patients with new crown disease to support immune cells against SARS-CoV-2.