Immune-boosting Nutrition and COVID-19

Given COVID-19 is a new virus, the evidence on best-practice nutritional support for those suffering from it is limited. But, some early research has highlighted the potential impact of nutritional status, through its critical role in immune function in general, on COVID-19 susceptibility and risk for severe infection.

Here, Accredited Practicing Dietitian, Amanda Smith, discusses are some of the key nutritional factors which research has shown play a potential role in COVID-19 risk and severity.

Malnutrition
Malnutrition is the primary cause of immune deficiency globally, with a strong relationship between malnutrition and infection documented in the scientific literature. When it comes to COVID-19, although the evidence is still emerging, malnourished individuals do have a higher mortality rate from COVID-19. Together, this suggests that malnourished individuals are more susceptible to infection with COVID-19, and to a greater severity.

In addition, given the impact COVID-19 infection can have on appetite, affected people won’t be achieving adequate protein-energy intake, which may delay recovery time.

Highly Processed Foods
High intake of highly processed, high saturated-fat, foods is prevalent in the Western diet. Research shows this can impair immunity, leading to chronic inflammation and reduced immune defences, both of which can increase susceptibility to infection. COVID-19 induced Inflammation may also be worsened by a high intake of highly processed foods such as chips, chocolate, soft drink, baked goods and fried foods.

Micronutrients
We know iron plays a key role in immune function, and it may also play a role in COVID-19 infection. Research shows an association between COVID-19 severity and iron-deficiency anaemia. There is limited evidence for the role of vitamin C, vitamin A and Vitamin E in COVID-19, including via supplementation. However, given the role these vitamins play in immune function, and the research highlighting the role antioxidants play in COVID-19 (see below), ensuring adequate dietary intake is still important.

Research does support the role of Vitamin D in preventing respiratory infections – there is association between Vitamin D deficiency and increased risk of respiratory infections. The potential benefits of supplementation of vitamin D for respiratory infections is inconclusive, so recommendations cannot currently be made. There does appear to be a role of Vitamin D in prevention and progression of COVID, however, more research is required.

Selenium has been studied for its antioxidant properties and role in immune function and viral infections. There is strong evidence that it plays a role in host-virus interactions, through its role as a co-factor in key antioxidant pathways. There is limited evidence for its use in COVID-19, but ensuring adequate dietary intake is still important overall. Tip – include 1 brazil nut per day to meet your selenium requirements!

Research suggests those with a zinc deficiency are more prone to respiratory infections. There is a small amount of data to show zinc sulfate supplementation may play a role in management of COVID-19, however, further research is required.

Overall, there is currently limited evidence of high-dose micronutrient supplements in the prevention or progression of COVI-19, however, clinical trials are currently being undertaken in this area.

Antioxidants
Severe COVID-19 infection can result in the production of high concentrations of free radicals which induces severe oxidative stress. Research shows oxidative stress is considered a key factor in the pathophysiology of severe COVID-19 infections. There is also higher levels of oxidative stress in individuals with co-morbidities such as diabetes, cardiovascular disease and obesity – which are associated with higher rates and severity of COVID-19.  Whilst the evidence in COVID-19 is limited, we know that antioxidants play an important role in reducing oxidative stress.

There is currently research being undertaken regarding antioxidant supplementation and COVID-19, and it is not yet clear whether dietary antioxidants will play a similar role. Whilst we can’t yet recommend supplementation of antioxidants for the management of COVID-19, increasing intake of antioxidant-rich foods certainly won’t hurt, and will be beneficial from an overall nutritional perspective.  Antioxidant rich foods include colourful fruits and vegetables, nuts and seeds, extra virgin olive oil, legumes, tea, herbs and spices, and wholegrains.

Plain Language Summary
COVID-19 is a new virus, and the research around nutritional management for this disease is still in its infancy. At this stage, there are no specific nutritional strategies for beating COVID-19, other than maintaining a healthy diet overall, low in highly processed foods, and with adequate protein-energy intake, especially if you’re suffering with COVID-19 infection.