The Immune System Function

The immune system is vital in protecting the body from harmful germs, substances, and changes in cells.  It is an extremely complex system which is always active, surveying the body for unwanted substances or changes in the body.  Its activity is heightened when an individual becomes infected with a virus, bacteria, and other harmful substances.

Vitamin and Mineral Support

An individual cannot “boost” their immune system, however there are several key vitamins and minerals that play an important role in supporting the immune system, and thus decreasing the risk of infections. These include vitamins A, B6, B12, folate, C, D and E, and trace elements zinc, copper, selenium, and iron. Each of these micronutrients play various roles in assisting antibacterial and antiviral defences, with zinc and selenium demonstrating a predominant importance in antiviral defence. It appears that the functioning of the immune system is compromised when there is a deficiency in these micronutrients.

Most of these micronutrients can be found in a variety of foods. The following commonly consumed foods contain one or more immune supporting micronutrients:

  • Green leafy vegetables (e.g. cabbage, spinach, broccoli, and kale)
  • Orange vegetables and fruit (e.g. carrots, sweet potato, butternut, oranges, peaches, mango and papaya)
  • Other fruits and vegetables: red and green peppers, strawberries, kiwis, potatoes
  • Beef (including liver), pork and lamb/mutton
  • Poultry
  • Fish, including oily fish, such as salmon and mackerel
  • Eggs
  • Dairy products
  • Beans, chickpeas and lentils
  • Nuts
  • Fortified cereals

Vitamin and Mineral Supplementation

For healthy individuals, who eat a varied diet, their daily requirements will be met for most micronutrients through the foods they eat. Vitamin D is one micronutrient where intake from food is likely to be inadequate. However, our bodies can create vitamin D from sunlight (direct sunlight on our skin).

Certain individuals are at greater risk for vitamin D deficiency, such as obese individuals, the elderly, strict vegans, individuals with limited sun exposure and individuals with darker skin.

Vitamin D status can be measured with a blood test for those individuals who are concerned about being deficient. The blood test is relatively cheap, around R200, and the results can assist in deciding on the amount of vitamin D to supplement with daily. An individual may be tempted to purchase a multivitamin supplement, however, although a wide range of nutrients can be obtained through a multivitamin supplement; these supplements often only contain small amounts of all micronutrients.  Therefore, the vitamin D requirements would not be met through most multivitamins. Fortunately, vitamin D supplements are readily available and can be taken daily to prevent future deficiencies.

Probiotics also play a part in immune support, and although probiotics can be found in food sources such as certain yoghurts, fermented foods and drinks such as kefir and Kombucha, there are a limited number of food sources, which are not always easily accessible.  Probiotic supplements may be an option for some individuals.  These are readily available at most health stores.


Supplementation should be looked at from an individualised approach, considering various factors including diet and lifestyle.  For example: I eat a varied diet, however, consume little red meat and fermented dairy products, and get minimal sun exposure during the winter months. So, this winter I will be stocking up on vitamin D supplements, a daily zinc and selenium tablet (i.e. not above the recommended dose of 8mg for zinc) and a probiotic. A dietician can assist individuals in deciding on the best supplementation regime for them, without wasteful expenditure.

Group Dietician

27 July 2020

Calder, P., 2020. Nutrition, immunity and COVID-19. BMJ Nutrition, Prevention & Health, 3(1), pp.74-92.
Publishing, H., 2020. Coronavirus Resource Center – Harvard Health. [online] Harvard Health. Available at: <> [Accessed 24 July 2020]. 2020. Office Of Dietary Supplements – Zinc. [online] Available at: <> [Accessed 24 July 2020].
Zeratsky, K., 2018. How Much Vitamin D Do You Need?. [online] Mayo Clinic. Available at: <> [Accessed 24 July 2020]