Nutrition and immunity: lessons from coronavirus disease-2019

Abstract

This review will provide an overview of the immune system and then describe the effects of frailty, obesity, specific micronutrients and the gut microbiota on immunity and susceptibility to infection including data from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic where relevant. A key role for the immune system is providing host defence against pathogens. Impaired immunity predisposes to infections and to more severe infections and weakens the response to vaccination. A range of nutrients, including many micronutrients, play important roles in supporting the immune system to function. The immune system can decline in later life and this is exaggerated by frailty. The immune system is also weakened with obesity, generalised undernutrition and micronutrient deficiencies, which all result in increased susceptibility to infection. Findings obtained during the SARS-CoV-2 pandemic support what was already known about the effects of ageing, frailty and obesity on immunity and susceptibility to infection. Observational studies conducted during the pandemic also support previous findings that multiple micronutrients including vitamins C, D and E, zinc and selenium and long-chain n-3 fatty acids are important for immune health, but whether these nutrients can be used to treat those already with coronavirus disease discovered in 2019 (COVID-19), particularly if already hospitalised, is uncertain from current inconsistent or scant evidence. There is gut dysbiosis in patients with COVID-19 and studies with probiotics report clinical improvements in such patients. There is an inverse association between adherence to a healthy diet and risk of SARS-CoV-2 infection and hospitalisation with COVID-19 which is consistent with the effects of individual nutrients and other dietary components. Addressing frailty, obesity and micronutrient insufficiency will be important to reduce the burden of future pandemics and nutritional considerations need to be a central part of the approach to preventing infections, optimising vaccine responses and promoting recovery from infection.

Unveiling the micronutrient‐immunity puzzle in inactivated COVID‐19 vaccination: A comprehensive analysis of circulating micronutrient levels and humoral responses in healthy adults

“…[1][2][3] Yet, their ability to induce robust immune responses can be significantly influenced by individual nutritional status. 4 Optimal nutrition serves as the bedrock for a competent immune system, including improvement in both innate and adaptive host immune function. 5 Based on current scientific evidence, several micronutrients, including six vitamins (A, folate, B 6 , B 12 , C, and D) and four minerals (zinc, iron, copper, and selenium), have been emphasized for their significance in maintaining normal immune function.…”

“…Vaccines have played a pivotal role as one of the most cost‐effective strategies in response to the coronavirus disease 2019 (COVID‐19) via mitigating severe disease and death 1‐3 . Yet, their ability to induce robust immune responses can be significantly influenced by individual nutritional status 4 . Optimal nutrition serves as the bedrock for a competent immune system, including improvement in both innate and adaptive host immune function 5 …”