Severe Covid-19 disease can be prevented

But we don’t hear about it.

May 6, 2020

“Immunity! Well, that comes naturally.”
Does it?

Now we are so far into the corona crisis that the first serious scientific results are beginning to emerge, and since no one else does, the Vitality Council will try to disseminate these results.
“Just throw people into the water. They will swim by themselves ”.
A foolish claim. It is well known that the chances of surviving a dive into the water increases if you have learned to swim.
But that is, in fact, what the (Danish) authorities are saying, now that they are opening up the country while coronavirus is still circulating.
They are throwing people into increased viral exposure because then it is thought that people automatically get built-up immunity.
Well, this may be true if people can defend themselves, that is, have a well-functioning immune system.
Without good immune defence, people have no chance.

The (Danish) authorities  know very well that there are large groups in the population that have a impaired immune system. And yet, they expect us all to sit with our hands in our lap without doing anything while we wait for a vaccine that stands as an angel of salvation on the horizon.
A vaccine may be excellent, but firstly, it takes at least a year before we have it, and secondly, a vaccine can never keep up with a virus in the many mutations that make its immune profile so varied that a vaccine quickly becomes obsolete as we have seen with the flu vaccine.
The only thing that can keep up with an adequate immune response against a virus’ mutations is a well-functioning immune system in the individual.
Despite the knowledge that many people have an impaired immune system, we have in the months that the corona crisis has lasted, not once heard the (Danish) authorities give the public advice on how to optimize the immune system.
If the population has a fundamentally strong immune system, then a virus will do less harm as the individual course of disease will be milder.
People still get infected and maybe sick too, but they don’t have to die from it.

Let’s start with the simple, Vitamin D3.

It is quite evident that the Covid-19 disease is massively over-represented in the northern hemisphere. Just like the annual flu epidemic, which ravages the northern hemisphere in precisely December to March, whereas it ravages the southern hemisphere from August to October – and why is that?
We can thank the Sun for that. It is high in the sky in the summer and charges our stores of vitamin D, so we have a strong immune system from June to November, and of course the other way around in the southern hemisphere. We never get the flu in July-August.

A second indication is that elderly people are at particular risk. Older people more often have a very low level of vitamin D in their blood, as they do not get much out in the sun.

A third indication is that obesity is at particular risk. Vitamin D accumulates in the adipose tissue, where it does not benefit the immune system. Overweight people must therefore have a significantly higher dose of vitamin D to achieve the same blood concentration as slim persons.

A fourth indication is that the disease is over-represented in immigrants, who often have severe vitamin D deficiency. On the one hand, most immigrants have dark skin, which allows less passage of sunlight, and on the other hand, many immigrant women are covered, even in the summer, when they need to get their annual vitamin D dose.

A fifth indication is that diabetics are also a special risk group. On the one hand, diabetics often have an impaired immune system, and, on the other, many diabetics receive cholesterol-lowering medication. If people lack cholesterol, you cannot produce vitamin D, even though the sun is shining sufficiently.

A sixth indication is approaching evidence in the case of a recently published observational study that compared mean vitamin D levels in 20 European countries with prevalence and mortality caused by Covid-19. There was significant negative correlation between vitamin D level and both prevalence and mortality. It was interesting to see that both morbidity and mortality approached 0 in those populations where the vitamin D level was above 75 nmol/L.
Vitamin D levels are seriously low in the aging population, especially in Spain, Italy and Switzerland. This is also the most vulnerable group of the population in relation to Covid-19.

A healthy diet with green vegetables is also important, as they contain magnesium, which is a prerequisite for activating vitamin D.
Magnesium is included four places in the synthesis as well as the activation and deactivation of vitamin D, so without magnesium, vitamin D is ineffective.

If you combine these indices with solid evidence that vitamin D3 is essential for a functioning immune system, it is not far off to propose a solid dose of vitamin D3 to optimize a suffering immune system in immigrants, diabetics, older and overweight people in particular.

In the past, people were nervous about overdosing on Vitamin D, but this has proved unfounded. Extremely high doses need to be taken over a long period of time before there is any risk. In the past, it was also thought that a vitamin D level of 50 nmol/L was sufficient in the blood, but this is too low.
If people want to be sure that the vitamin D level is sufficient for an optimal immune system, the level should be between 75 – 150 nmol/L.

This newsletter is the first about some of the factors in our environment, nature, surroundings and diet that can optimize our immune system and thus reduce the risk of serious Covid-19 disease.
The next will deal with the latest research on selenium and Covid-19 disease.

Take care of yourself and others!

Claus Hancke; MD, Specialist in general medicine


  • Hewison M. Vitamin D and innate and adaptive immunity. Vitam Horm, 2011; vol 86:23-62.
  • Gombart AF, Pierre A, Maggini S. A Review of Micronutrients and the Immune System-Working in Harmony to Reduce the Risk of Infection. Nutrients. 2020 Jan 16;12(1).
  • Schwalfenberg GK. A review of the critical role of vitamin D in the functioning of the immune system and the clinical implications of vitamin D deficiency. Mol Nutr Food Res. 2011 Jan;55(1):96-108.
  • Dancer RC, Parekh D, Lax S, D’Souza V, Zheng S1, Bassford CR, et al. Vitamin D deficiency contributes directly to the acute respiratory distress syndrome (ARDS). Thorax. 2015 Jul;70(7):617-24.
  • Urashima M, Segawa T, Okazaki M, et al. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 May;91(5):1255-60.
  • Sabetta JR, DePetrillo P, Cipriani RJ, Smardin J, Burns LA, Landry ML. Serum 25-hydroxyvitamin d and the incidence of acute viral respiratory tract infections in healthy adults. PLoS One. 2010 Jun 14;5(6):e11088.
  • Uwitonze AM, Razzaque MS. Role of Magnesium in Vitamin D Activation and Function. J Am Osteopath Assoc. 2018 Mar 1;118(3):181-189.
  • Valint S. Vitamin D and Obesity. Nutrients. 2013 Mar; 5(3): 949–956.
  • McCartney DM, Byrne DG. Optimisation of Vitamin D Status for Enhanced Immuno-protection Against Covid-19. Ir Med J. 2020 Apr 3;113(4):58.
  • Grant WB, Lahore H, McDonnell SL, Baggerly CA, French CB, Aliano JL, Bhattoa HP. Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients. 2020 Apr 2;12(4). pii: E988.
  • Aldridge RA, Lewer D, Beale S, et al. Seasonality and immunity to laboratory-confirmed seasonal coronaviruses (HCoV-NL63, HCoV-0C43, and HCoV-229E): results from the Flu Watch cohort study 30 March 2020.
  • McCullough PJ, Lehrer DS, Amend J. Daily oral dosing of vitamin D3 using 5000 TO 50,000 international units a day in long-term hospitalized patients: Insights from a seven year experience. J Steroid Biochem Mol Biol. 2019 May;189:228-239.
  • Ilie PC, Stefanescu S, Smith L. The role of Vitamin D in the prevention of coronavirus disease 2019, infection and mortality. Aging Clinical and Experimental research ( Springer Switzerland. 2020 May 6.