COVID-19 is a respiratory disease caused by the novel coronavirus, SARS-CoV-2, that has reached pandemic status (1). The following article tends to address the role of diet and nutritional supplements during Covid-19.

The clinical course of COVID-19 disease tends to be more severe among older individuals and among people with chronic conditions, such as cardiac disease and immunosuppression (2)

The high prevalence of these risk factors is likely to be driven by increasing consumption of the western diet consisting of high amounts of saturated fat, refined carbohydrates and sugar and low levels of fibre, unsaturated fats and antioxidants (1).

The western diet can lead to chronic activation of the innate immune system and. This relates to an increase in inflammation and tissue damage in the body. Also, a decrease in host defence against viruses (1).

Consuming good quality diets is always desirable, and this is particularly important during the COVID-19 pandemic. A healthy diet emphasizes fruits, vegetables, whole grains, legumes, nuts, dairy produce and good quality fish, poultry and red meats. What should be avoided is processed meats, sugar and refined carbohydrates and an excessive intake of saturated fats. Added fats should be primarily olive oil, canola- or soybean oil (2). Studies show that consuming healthy foods has a rapid anti-inflammatory effect, even in the presence of obesity pathology (2).

Keeping your immune system healthy year-round is key to prevention of infection and disease. Making healthy lifestyle choices by consuming nutritious foods, getting enough sleep and exercise are the most important ways to boost your immune system (3).

In addition, research has shown that supplementing with certain vitamins, minerals, herbs and other substances can improve immune response and potentially protect against illness (3).

Supplementation cannot cure or treat COVID-19 but there is existing evidence on specific nutrients in relation to other infections and positively influencing the immune system (4).

Nutritional Supplements that are known for their immune-boosting potential.

The following should form part of the daily diet and nutritional supplements during Covid-19.

Vitamin C

It has been known for since the 1940 ’s that taking higher doses of vitamin C both prevent and reduce the effects of the common cold if you started taking it regularly before contracting the virus (5). Vitamin C prophylaxis does appear to reduce the duration and the severity of colds, but not the incidence (4).

Vitamin C supports the function of various immune cells and enhances their ability to protect against infection. It is also necessary for cellular death, which helps keep the immune system healthy by clearing old cells and replacing them with new ones (3). Vitamin C also functions as a powerful antioxidant, protecting against damage induced by oxidative stress that can negatively affect immune health (3).

Supplemental daily doses range between 300 and 1000 mg.

Vitamin D

Clinical studies show that vitamin D supplementation helps protect against respiratory tract infections (3, 4). These studies included both seasonal and pandemic flu, caused by the H₁N₁ virus in 2009. The beneficial effect of supplementation was seen in patients across all ages, and individuals with pre-existing chronic illnesses (2).

Supplemental daily doses range between 1000 and 4000 IU.

Zinc

Zinc plays an important role in maintaining healthy immune function (5). It is needed for immune cell development and plays an important role in the inflammatory response (3).

Numerous studies reveal that zinc supplements may protect against respiratory tract infections. Shortening the duration of flu-like symptoms and improving the rate of recovery (2,3).

 Supplemental daily doses range between 20 and 90 mg.

Selenium

Selenium is a mineral that is essential for the adequate functioning of the immune system. Dietary selenium supplementation of patients with low selenium status might contribute to support the pro-inflammatory cellular immune response against viral and bacterial pathogens. However, driving the macrophages towards a more anti-inflammatory reaction (8).

Supplemental daily doses range between 40 and 80 µg.

Echinacea

There is some evidence, that Echinacea improves immune health. The resultant antiviral effects against several respiratory viruses. This includes respiratory syncytial viruses and rhinoviruses (3, 4).

Quercetin

Quercetin is one of the better-known flavonoids from the flavanol subfamily. A major health benefit of quercetin comes from its antioxidant and anti-inflammatory properties. Higher doses of Quercetin has been shown to reduce upper respiratory tract infections in older adults (6).

Olive leaf extract

Olive leaf extract, derived from the leaves of the olive tree, contains phenolic compounds, specifically oleuropein. These have demonstrated potent anti-microbial, antioxidant, and anti-inflammatory activity. Oleuropein and derivatives were shown to be effective against numerous micro-organisms, including influenza and parainfluenza. Olive leaf extract has also been shown to stimulate phagocytosis, thereby enhancing the immune response to viral infection (5).

Pelargonium sidoides

Pelargonium sidoides (African geranium) is a plant which has popular usage for the treatment of respiratory-related ailments such as bronchitis and asthma. They are used not so much for the prevention of colds but to reduce the respiratory symptoms of colds and flu (7).

The African Geranium appears to have direct inhibitory properties on viral replications, with more promise on some strains of seasonal influenza (H₁N₁ and H₃N₂) but not on avian influenza (H₅N₁) and good promise on respiratory syncytial virus (RSV). It appears to quite potent at inhibiting viral replication and good promise on herpes simplex associated with preventing adsorption of the virus (7).

In both children and adults with acute bronchitis, supplementation of Pelargonium sidoides appear to be highly effective in reducing respiratory side effects (7).