Nutrition is key to global pandemic resilience

Birgisdottir, Bryndis Eva

Correspondence to Dr Bryndis Eva Birgisdottir, Unit for Nutrition Research, Faculty of Food Science and Nutrition and Landspitali-University Hospital, Haskoli Islands, Reykjavik, Iceland;[e-mail] Healthful food of good quality is our first line of defence against diseases,1 including immune defences against pathogenic organisms.2 3 In the current worldwide concern of coronavirus SARS-CoV-2, resulting in the COVID-19 disease, a sturdy immune system is considered central.4 This inevitably puts focus on the saga of the harmonious concert between nutrition and the immune system, unfolding over the last century.2 Big pandemics and resourceful pathogens have shaken the world before, with devastating death tolls of often young people, such as through the Spanish influenza and tuberculosis.5 6 Although biological processes or mechanisms were less understood at the time, it was simply considered common sense that those who had access to enough quality food had a better chance against diseases. Later, or mid-century, the extended and cyclical relations between malnutrition and infections were elegantly described,2 and diabetes was also early identified as a condition making people especially vulnerable to pathogens.7 An interwoven world Today, however, the increasing diversity of reliable quality tools that are available to assess immune function have facilitated the remarkable increases in our comprehension of the design of both the innate and adaptive immune system.2 Scientific advances have also brought with them an emerging understanding of the web of genes, the immune system and nutritional status, including energy metabolism and the gut microbiota, although many puzzles still remain to be solved.3 8 The current challenge is to capture the complexity of this multidimensional relationship, interacting via multiple direct and indirect pathways,3 while at the same time tracing and understanding the effect of single nutrients of special importance.9 10 As the immune system develops and forms from conception to adulthood,3 a natural decline in immune function is usually inevitable with age.4 However, this decline may be slowed through optimal nutrition, as well as optimisation of other lifestyle factors such as physical activity and sedentariness, stressors and sleep, throughout the life course.9 All are of great importance. The importance of these are bluntly reflected in food-based dietary guidelines (FBDGs), represented as recommendations for a variety and diversity of whole vegetables, fruits, berries, nuts, seeds, grains and pulses, along with some meats, eggs, dairy products and fish, if selected, as discussed in the paper by Calder.4 This type of healthy diet is a tactical aproach to build a healthy body and a strong immune system, as emphasised by the WHO and other organisations during the pandemic,18 especially when eaten at the expense of more ultraprocessed food items.19 Nutrition is a balancing act Furthermore, the diet described previously would for most people provide ample amount of the micronutrients that have been suggested to be of special importance for the immune system.4 However, vitamin D as one of the key micronutrients for the immune system has been given special focus by several papers in the collection.12 13 The vitamin is found in only an handful of foods and populations with low sun exposure have been found to be prone to low status, especially during the winter months. Special conditions: clinical setting However, with advancing age and for high-risk groups, a nutrient-rich diet is not always enough to meet needs for micronutrients.4 14 While high intakes should be avoided, there may be a a role for immune-targeted supplements that might be necessary to achieve the intake of nutrients needed for an optimally functioning immune system.4 Furthermore, there is one thing to enhance the public health nutritional status, through preventive actions, while the clinical situation of an active disease is another situation altogether.