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Protecting Immunity

Part One – Vitamins and Minerals

I’ve been asked a lot recently “what can I eat to protect myself from viruses and why do some people seem to suffer with COVID-19 symptoms more than others”. I don’t believe there are definitive answers yet to these questions but this is a timely moment to share some of the latest research on the observational links to vitamin and mineral deficiencies and COVID-19 symptom outcomes.

Vitamin D

There is a striking overlap between risk factors for severe COVID-19 outcomes and vitamin D deficiency, including obesity, older age, and Black or Asian ethnic origin, which led researchers to look closely at vitamin D supplementation as a preventive agent for COVID-19. The lancet 3rd August 2020. Many more studies in the past four weeks are repeatedly reporting that low levels of vitamin D are consistently associated with high susceptibility to COVID-19 infection.

Treatment of acute respiratory infections dates back to the 1930s, when cod liver oil was investigated as a means to reduce industrial absenteeism due to the common cold.

Why: Vitamin D supports the immune system and reduces inflammation

In order for our body to process vitamin D from the food we eat we require a good level of natural sun light and good quality vitamin D content from foods such as fatty fish - salmon, mackerel and sardines also eggs, mushrooms and cow’s milk.

It’s important to get good levels from your diet so eating this type of fish at least four times a week will ensure you get adequate levels. If you are unable to get good natural light during the day and your food intake of vitamin D food is limited, supplementation is recommended at 1,000 IU per day or higher if you have been tested and are low.


Diets low in zinc can induce measurable reductions in the activity of the immune system. It appears that the elderly are especially prone to developing reduced immunity related to poor zinc nutrition, however in this at-risk population restoring zinc status appears to reverse the lowered immune function within weeks.

Infections, trauma and stress depletes our store of zinc as does the use of steroid medications. Those with gastrointestinal problems also have impaired zinc absorption particularly those with inflammatory type bowel disorders.

Good sources of zinc:

Include beef, spinach, asparagus, mushrooms, lamb, sesame and pumpkin seeds, nuts and legumes. Generally like other minerals zinc is stable and not lost when cooked.

Supplementation should not exceed 25mg per day and could help if you feel you are coming down with viral symptoms.


Selenium is another essential mineral of high importance for human health and particularly for a well-balanced immune response. This mineral and its action to support the immune system has been studied for several years. In the past few months reports from a number of university Hospitals studying COVID-19 patients are showing a significant link to low levels of Selenium in those who managed the virus less well. These are observational studies but they still help us to make better informed decisions about the food we eat and the need, in certain situations, for supplementation.

The selenium content of plant foods is often closely related to the selenium content of the soil within which they are grown, and this varies widely.

Foods high in selenium include:

Sardines, salmon, cod, mushrooms, asparagus, chicken, lamb, scallops, tofu, brown rice, eggs, sunflower seeds, sesame seeds, flaxseed and garlic.

Dietary selenium intakes in the UK have fallen over the last 20 years and are below those in many other countries The Journal of Nutrition, Marginal Dietary Selenium Intakes in the UK. Digestive problems and some drugs can prevent the absorption of selenium so supplementation is recommended in these situations at 100ug per day.

Vitamin C

We don’t make vitamin C in our body and rely every day on the correct dietary consumption of this important immune supporting vitamin.

There are currently 37 studies on vitamin C and its clinical relevance to COVID-19 on the Clinicaltrials.Gov website, all supporting its positive effect on COVID-19 outcomes, particularly reducing symptom severity. Good sources include Papaya, peppers, Brussels sprouts, strawberries, oranges, kiwifruit and cantaloupe melon.

There is no doubt this vitamin should be part of your daily diet or supplement intake. Taken daily as a preventative supplement vitamin C is effective at 500mg.

Thiamine Vitamin B1

Several recent studies have shown that thiamine is able to improve immune system function and in a deficient state it increases inflammation and leads to abnormal antibody responses.

B vitamins are water soluble and quickly pass through our body so it’s really important to consume B vitamins daily.

Good sources of vitamin B1 comes from asparagus, sunflower seeds, green peas, flax seeds and Brussels sprouts, all of which supply good levels per weight as well as legumes, nuts, oats, tofu. Vitamin B1 is fragile and easily damaged by heat during cooking so try to incorporate flax and or sunflower seeds into a smoothie as a safe way to preserve its content.

Do also note: as well as stress the regular consumption of tea and coffee quickly depletes all B vitamins through the action of an enzyme which binds and removes these very important vitamins. If you drink regular tea or coffee or are not able to consume a regular varied diet please do consider a vitamin B complex containing all B vitamins.

For further advice on the level of supplementation that is supportive for you considering your age and related conditions please contact Henley Nutrition.

Henley Nutrition, September 2020



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