Coronavirus (Covid-19)

20 Apr 20

Coronavirus (Covid-19) and the Immune System

The Coronavirus (Covid-19) is a new virus our immune system is learning to fight. The immune system is complex and ‘Boosting’ the immune system is misleading:  You do not want an overactive or underactive immune system but you do want to optimise your immune system.  A lifestyle of balanced eating combined with physical activity and adequate sleep contributes to a healthier immune system.

Vitamin and minerals involved in the immune system are vitamin A, vitamin D, vitamin C, vitamin B6, vitamin B12, zinc, folate, iron, selenium and copper.  Therefore, if you don’t have a balanced diet, have low Vitamin D or are genuinely deficient, it may be worth blending/juicing or considering taking a supplement.  Please seek advice from a dietitian or appropriate health professional.  More does not always mean better and can be harmful.  If you are unsure what a healthy balanced diet is; please see BDA Food Facts on Healthy or Plant Based eating.

Vitamin C has received the most attention because an unpublished Chinese study was endorsed by its Medical Association.  It involved high dose Vitamin C delivered intravenously (via the vein) in a hospital setting to people with severe lung infections.  A subsequent trial is pending.  It’s known Vitamin C may help reduce the risk of getting the common cold in training athletes, who may suffer from supressed immune systems due to the high level of physical exercise.  For the rest, vitamin C may reduce severity or duration of the common cold if taken before onset of symptoms.  It may also reduce pneumonia severity and hospital length of stay in individuals with low vitamin C.  Adult daily recommended intakes are 40mg and it is recommended doses do not exceed 1000mg per day.  The dose amounts suggested in most studies are greater than 200mg but less than 2g.  200mg is easily achieved with five 80g daily servings of fruit or vegetables. 

Rich sources of Vitamin C (per 80g): 

Raw guava180mg
Peppers and stewed blackcurrants90mg
Glass of orange juice80mg
Spring greens, strawberries60mg
Curly kale, boiled brussels sprouts,50-60mg
Paw paw, kiwi, clementine and Orange40-50mg

High supplement doses of Vitamin C may cause kidney stones and those with acute pancreatitis should seek medical advice.

Zinc. In adults, zinc acetate doses of greater than 75 mg/day taken after the onset of a cold until the cold is gone may reduce overall cold duration and the duration of some symptoms.  Note, it’s only for the duration of the cold.  In children, daily prevention doses of 10-15 mg zinc may slightly decrease the risk of getting a cold.  These are high doses; above the upper recommended amount of 25mg/d for adults.  Normal child doses are dependent on age and gender (between 4.0-9.0mg).  High doses could have harmful side effects, so perhaps better obtained through diet.

Vitamin D It’s difficult to get sufficient Vitamin D from food.  Our skin makes it in response to sunlight, but in the UK this can only happen between April to September.  All adults and children over the age of one should consider taking a daily supplement containing 10 micrograms of Vitamin D especially during autumn and winter and for under one year olds it depends on whether they are on a milk formula.

Vitamin A is associated with an increased risk of lung cancer in smokers and may be harmful in pregnancy and therefore supplements containing Vitamin A are not recommended in pregnancy. Regular high doses of B6 could cause nerve damage.   Selenium looks beneficial in mice studies but in humans has positive and negative effects on the immune system.  The good news is that you only need 2 brazil nuts per day for adequate selenium.

Rich sources of Zinc

Meat (particularly brown or organ cuts) per 90g



Tinned crab 85g

Tinned sardines

Prawns 60g

Plaice cooked 150g


5 mg




Nuts and seeds per handful

Nuts, Cashews, Pecans

Brazil nuts, peanuts and almonds





Shredded wheat x2 biscuits and all bran

Tofu 100g

Cheddar cheese matchbox size 30g

Dried beans or cooked lentils 3 tablespoons






Probiotics.  Microbiota (good and bad bacteria) that lives in your intestines can weigh up to 2kg of the adult human body and their main function is modulation of the immune system.  Whilst there are common strains to all, microbiota status varies from person to person. Good and bad bacteria are in competition with each other, so, it makes sense to skew the balance to good.  Probiotics (good live bacteria) can be found in yogurts and fermented milks and supplements. There is a lack of conclusive evidence supporting the use of probiotics in preventing cold and flu. However, probiotic products are generally safe for those in good general health and may reduce the risk and duration of a cold.  Seek advice if you are immunocomprimised before taking a probiotic. Studies showing positive effects typically use levels above 108 CFU and use specific strains such as Lactobacillus casei rhamnosus.  It also makes sense to feed your good bacteria with prebiotics (the food for beneficial bacteria). Prebiotics are fermentable fibres and naturally present in fruit, vegetables and wholegrains.


Juicing. Juicing fruit and vegetables can contribute to antioxidant status and immune functions; after-all, it does come from fruit and vegetables.  So why not eat the whole fruit and get the benefits from their fibre as well.

Alkaline Diet. The alkaline diet (which includes apple cider vinegar and lemon juice) is based on flawed thinking that acid-based food causes a variety of different diseases and disorders.  The body tightly maintains pH and whilst high protein foods may have an influence on urine pH, it does not change blood pH outside of the normal range.

Ketogenic Diet. The Keto is a low carbohydrate diet with most of the body’s energy requirements met by fats.  Benefits have only been shown in mouse models.

Broth. Soup has long been regarded as a remedy for colds and flu.  Soup is comforting and contains a number of beneficial substances which may also be derived from other ingredients such as vegetables!  The fluid would also help with hydration.



Elderberries.  Most of the research has been done on cells in labs or in animals and there are very few human trials. In air travellers, it may not reduce the risk of getting the common cold but the duration.  A summary of human trials (of only 180 participants) concluded that elderberry supplementation reduced upper respiratory cold and flu symptoms.

Echinacea . Although popular, there is a lack of convincing evidence to suggest that echinacea products are effective for preventing or treating the common cold in adults or for preventing or treating these in children. 

Spirulina. Spirulina is a type of blue-green algae not a superfood.  There is no such thing as a superfood.  However, its benefits do look interesting in a laboratory dish but unfortunately most these benefits have not translated into human studies.  In humans, there is reason to believe it may be beneficial with symptom management in certain people including those with allergies and nasal congestion. 

 Garlic supplementation at best may reduce duration but the evidence is mixed and too few. Enjoy it in your cooking!