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Rapid response to:


Preventing a covid-19 pandemic

BMJ 2020; 368 doi: (Published 28 February 2020) Cite this as: BMJ 2020;368:m810

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Rapid Response:

Re: Preventing a covid-19 pandemic

Dear Editor,
As we approach a time when retired health professionals are invited to rejoin their younger colleagues would it not be wise to offer them protection from the novel corona virus ? Dr Rhein highlights the 2017 BMJ study on D3 by Martineau et al and the safety of dosing with 100ug D3 per day (=4000 IU). The text below has been submitted to a national broadsheet paper. Supplies of D3 are likely limited and D2 may not be an effective subsittute. The vast majoriity of UK elderly fail to reach physiological levels of 25(OH)D3 so bolus dosing may be needed by those older volunteers to endow them with an effective defense form the virus.
COVID-19 and D3
As a 75 year old cell biologist with impaired health I know I have an unacceptable existential risk from COVID-19. I supplement with vitamin D3. To understand why, we need to look into the biology of this hugely important hormone.
Amongst the 5000 research articles published annually on vitamin D3 is one common feature, for the past decade they mostly begin with “The secosteroid hormone D3.....”. As a hormone D3's natural, physiological blood level can be defined scientifically. There is interminable debate by health bodies globally about the correct blood level and how much D3 is needed in diet and from sunlight. The overarching importance of the physiological level of this hormone is still being lost to the persisting, out of date, assumption that D3 is a vitamin whose dosage can be determined as if D3 were a drug. D3 is not a drug whose minimally effective dose governs the debate. That approach risks advising too little, leaving us deficient. D3 is a hormone with a 400 million year evolutionary history which exerts a broadly defensive role in almost every cell in our body by controlling the expression of 2000 genes, one in ten of our genome. The physiological blood level of D3, which is measured routinely as 25(OH)D3, has been determined by several criteria to be 100 to 125 nmol/l (“ nano moles per litre”, a unit of concentration). This talk by the late Professor Robert Heaney MD describes how he and a committee of experts defined the physiological level:
There are key pointers in the literature that I am raising my blood D3 level high enough to protect from the corona virus that causes COVID-19. There are many clinical trials of supplementing with D3 that have failed to influence 'flu. I place especial emphasis on two 'flu studies in which serum 25(OH)D3 met the physiological criterion of 100 to 125 nmol/L.
“A colleague of mine and I have introduced vitamin D at doses that have achieved greater than 100 nmol/L in most of our patients for the past number of years, and we now see very few patients in our clinics with the flu or influenza like illness.”
“Maintenance of a 25-hydroxyvitamin D serum concentration of 38 ng/ml or higher should significantly reduce the incidence of acute viral respiratory tract infections significantly....”
(38 ng/ml is 100 nmol/L and physiological )
We have a pretty good idea of how D3 combats microbes. One action is to promote production of anti-microbial peptides, including cathelicidin and defensins, that attack the membranes of bacteria, fungi and enveloped viruses, and kill them. Influenza and corona viruses are enveloped. The COVID-19 virus is unlikely to avoid these defences, but the lack of lab' data on this new virus offers a loophole to cautious authorities.
My remaining question was: am I taking enough D3 supplements to reach that physiological blood level? The literature points to around 2000 International Units per day of D3, or maybe 4000 IU pd for the elderly who take it up less well from the gut. Sunbathing before May in UK wont make significant D3. Dietary intake in UK averages merely 200 IU pd. A tin of sardines including the oil contains about 2000 IU. Unfortunately there is a snag: it takes 2 to 3 months for the blood level to fully stabilise after boosting uptake. So blood D3 rises too slowly to help anyone infected in the next month, even if supplements started now. Bolus administration is feasible under medical advice. Of course, supplementing D3 is not a substitute for the hygiene and social measures advised by the governments.

Competing interests: No competing interests

08 March 2020
Peter H Cobbold
Emeritus Professor, Cell Biology
University of Liverpool, UK
North Wales