The spread of novel SARS-CoV-2 virus has increased interest on the role of the immune system, leading to a large number of claims around supplements and certain foods that can help combat the virus by ‘supercharging’ the immune system. To help address some of these misconceptions around nutrition, immunity and COVID-19, Professor Philip Calder, Professor of Nutritional Immunology within Medicine at the University of Southampton, hosted a Nutrition Society Training Academy (NSTA) webinar on 27 April.
Whilst it is clear that diet, nutrition and nutritional status are very important in supporting the immune system to combat a virus if infected, Professor Calder stressed there is no individual nutritional supplement that will stop a person contracting highly infectious viruses like COVID-19.
The immune system is one of the most complex bodily systems, made up of a network of cells, molecules, tissues and organs that have evolved a range of different functions that enable them to deal with the diverse pathogens present in the environment. This complexity means that as well as nutritional status, there are a huge range of other factors including genetics, stress, time of day, age and obesity that can affect the immune response and the system cannot be modified acutely by any one specific nutritional intervention (1)(Figure 1).
Fig.1. Factors affecting immune response (Calder, 2020)
Professor Calder explained the progressive increase in COVID-19 related mortality seen in those above the age of 60 is likely the result of immunosenescence, the immune decline that occurs with age, whereby the thymus shrinks, resulting in fewer and less effective T cells in the circulation and a reduced thymus output. He added that the reason obese individuals appear to experience more severe COVID-19 symptoms (2) may be partly due to an impaired immune response in overweight and obesity(3).
He added: “A well-functioning immune system is key to providing robust defence against pathogenic organisms”
While vitamin C and zinc supplements may be flying off the shelves, it is important to remember there are a whole range of nutrients involved in supporting the immune system. Being infected increases the body’s demand for energy and nutrients. Energy is required to fight the virus, building blocks (e.g. amino acids) to produce essential antibodies, and a variety of nutrients such vitamins A, C and E, along with the minerals zinc, copper and selenium to help regulate the immune response.
The best way to support your immune system is to maintain a healthy, well balanced diet with plenty of plant based foods rich in vitamins and minerals, plus some animal based foods which are rich in essential fatty acids and B12. High fibre foods that promote microbiome diversity in our large intestine are also importance for immunity as healthy gut microbiota has been shown to play a key role in the body’s immune response (4).
Supplements cannot substitute a healthy diet
Whilst it may be tempting to stock up on supplements, there is no evidence that specific foods, supplements or commercial probiotic products can prevent or treat viral infections. Many of the studies looking into specific nutrients are often carried out in animals using doses that are not easily achievable through diet, are not able to be properly absorbed by the body or are toxic at high doses.
Much still remains to be known about the influence of nutrition and dietary intake on COVID-19. If you are concerned that your diet does not provide all the nutrients you need, it is important that you seek advice from a dietitian or other healthcare professional and follow the current advice set out by the Government, NHS and Public Health England.