By Sarah Bennett of Sarah Bennett Nutrition

There has been some interesting research lately about vitamin D and covid-19.

While it is by no means a cure for the virus, the research relates to the benefits of the vitamin and immune response.

We all know vitamin D is essential and immune support is just one important function of it.

Vitamin D deficiency is very common, especially in the UK (less UV radiation in the atmosphere so less reaching skin to be converted) and even if you are outdoors a lot in the summer months, wearing clothing and sunscreen can impact absorption.

Vitamin D deficiency has been shown to be associated with acute viral respiratory infection and pneumonia and that supplementation has been shown to reduce the risk of respiratory infection, so a deficiency may contribute to increased risk of respiratory infection from Covid-19.

It has been recommended that all older adults, hospital inpatients, nursing home residents and other vulnerable groups e.g. those with diabetes, compromised immune function, darker skinned, those who are overweight or obese, smokers and healthcare workers to be supplemented with Vitamin D to enhance the resistance to covid-19

Groups of people who are likely to already have low concentrations and could benefit from higher concentrations include, pregnant women, the obese, people with chronic diseases, and the elderly.

Vitamin D supplementation might be a useful measure to reduce risk, but to be clear, this is not is intended is a cure all solution for Covid-19 and the most important preventative advice relates to physical distancing, proper hand hygiene and cough sneeze etiquette.

Also, interestingly, evidence supporting the role of vitamin D in reducing risk of COVID-19 includes:

• The outbreak occurred in winter, a time when vitamin D concentrations are lowest
• The number of cases in the Southern Hemisphere near the end of summer are low
• Vitamin D deficiency has been found to contribute to acute respiratory distress syndrome
• Death rates increase with age and with underlying health conditions, both of which are associated with lower vitamin D concentration.

This study was published in April (see table) detailing the current research in support of higher vitamin D serum levels and decreased incidence of viral-induced respiratory diseases.
It involved patients who had been hospitalized in three separate hospitals in Southern Asia.

Vitamin D levels were grouped as:
1. Normal –30 ng/ml (75 nmol/L) or above
2. Insufficient –21-29 ng/ml (51-74 nmol/L)
3. Deficient –below 20 ng/ml (50 nmol/L)

Cases were all confirmed for COVID-19 and were grouped as:
1. Mild – presenting with mild clinical symptoms and no diagnosis of pneumonia
2. Ordinary – presenting with fever, respiratory symptoms, and a confirmed diagnosis of pneumonia
3. Severe – cases with hypoxia and respiratory distress
4. Critical – cases with respiratory failure requiring intensive care

From this study they found, the average vitamin D level of all 212 cases was 24 ng/ml (59 nmol/L).
Of all COVID-19 cases, 86% of all cases among patients with normal vitamin D levels were mild, while 73% of cases among patients with vitamin D deficiency were severe or critical.

They concluded that the vitamin D level in the body could account for the clinical outcomes of the patients infected with Covid-2019.

An increase in vitamin D level in the body could either improve clinical outcomes or mitigate worst (severe to critical) outcomes.

On the other hand, a decrease in vitamin D levels in the body could worsen clinical outcomes of Covid-2019.


Obviously a lot more research needs to be done, however the advice to take a vitamin D supplement still seems sensible considering the current low vitamin D levels across the population and the fact so many of us are getting less daylight than usual, but as always this will be individual so speak to your GP if you are unsure.

Vitamin D should remain a priority for maintaining a healthy immune system and optimal overall health.

It is important to remember though, this won’t be a cure-all for COVID-19 & it is vital to follow the main public advice related to hand washing, cough/sneeze etiquette & physical distancing.

A daily vitamin D intake of 1000–4000 IU (25–100 micrograms) should be enough to ensure optimal blood levels for most people.

Any brand of vitamin D3 supplement is fine to use. 1 microgram of vitamin D = 40 international units (IU).

NB: N= in the table denotes number of subjects in study.

Guidelines for blood levels of vitamin D are:

Optimal: 30 ng/ml, or 75 nmol/L.
Safe upper limit: 60 ng/ml, or 150 nmol/L.
Toxic: Above 150 ng/mL, or 375 nmol/L.

Sarah B