Effects of diets, foods and nutrients on immunity: Implications for COVID‐19?

Abstract

The COVID‐19 pandemic has sparked an increase in claims that particular food and drink products and nutritional supplements are able to ‘boost’ immunity. The immune system is highly complex, consisting of many different cell types and processes, and nutritional adequacy is undoubtedly required to support its function. Specific roles have been established for several micronutrients including vitamins A, B6, B12, C and D, copper, folate, iron, selenium and zinc, with documented impacts on particular aspects of immune function as a result of clinical deficiencies. Increased susceptibility to infections and poorer outcomes have been commonly observed in cases of undernutrition. However, high bodyweight, diabetes and ageing are also associated with immune dysfunction. The gut microbiota is intimately linked with the immune system and there is some evidence to suggest that food components that favourably modify its composition, such as pre‐ and probiotics, may be advantageous in immune modulation. Studies also indicate some benefits of specific supplements; for example, zinc and vitamin C supplements have been shown to reduce the duration of the common cold; probiotics have been suggested to reduce the duration and severity of acute infectious diarrhoea and prevent antibiotic‐associated diarrhoea; and anti‐inflammatory effects of long‐chain omega‐3 fatty acids have also been demonstrated. However, at present there are no authorised EU health claims for any of these effects. In the light of the recent media interest in the role of diet and lifestyle on the immune system following the COVID‐19 outbreak, this article will summarise why a healthy, balanced diet is key to supporting immune function with consideration given to the latest thinking in relation to COVID‐19.

Flight attendant occupational nutrition and lifestyle factors associated with COVID-19 incidence

“…It is well known that dietary intake is vital for optimal health. Eating a well-balanced diet is crucial to obtain all the daily nutrient recommendations necessary for enhanced immune health and improved overall health status 33 , 34 . The WHO has suggested an increased intake of fruit and vegetable consumption beyond pre-pandemic recommendations during this time period to lower the risk of potential infection 35 .…”

Role of Nuclear Factor Erythroid 2 (Nrf2) in the Recovery of Long COVID-19 Using Natural Antioxidants: A Systematic Review

“…Many claim that nutritional supplements in the form of food or drinks can increase immunity, especially during the COVID-19 pandemic [ 81 ]. As it relates to oxidative stress, a person’s nutritional status has a major impact on the immune system and on the development of comorbidities that are considered risk factors for COVID-19 [ 82 ].…”

Vitamin D: What's new a year on from the COVID‐19 outbreak?

“…To support normal immune function, the body requires adequate energy and nutrition (Calder, 2020), and specific roles have been demonstrated for a number of vitamins, trace elements, amino acids and fatty acids, which together contribute to the body's immune defences, including ability to reduce risk of infections (Calder, 2020). For example, the European Commission has approved health claims for vitamin A, vitamin B6, folate, vitamin B12, vitamin C, vitamin D, zinc, selenium, iron and copper recognising their contribution to the normal function of the immune system (EC, 2021) (see Lockyer, 2020 for more details on these nutrients and their role in immunity). However, early on in the pandemic, the spotlight landed on vitamin D presumably because vitamin D status is typically lowest in late winter when respiratory tract infections peak (Berry et al, 2011; Lanham‐New et al, 2020).…”