Week 11 - An interesting, missing piece of the jigsaw

Topic suggested by Alison Cobb

 

Although ‘Vitamin D’ (calciferol and cholecalciferol) is often referred to as a vitamin, it is also a prohormone, because it can be synthesized by the body. It is found in liver and in fish oils, and is essential for the prevention of rickets and osteomalacia. Vitamin D is produced in the skin during exposure to sunlight (UVB radiation at 290–315 nm) with, usually, smaller amounts obtained from food. During the winter months in the UK the solar elevation remains low throughout the short daylight period, and there is insufficient solar UVB to support appreciable synthesis of the vitamin. For most people, dietary intake does not fully supply the body’s vital needs and so vitamin D status declines during the winter. Older, housebound individuals are at particularly high risk. There is evidence that lower vitamin D status is associated with acute respiratory tract infections. A large cross-sectional study of the US population reported that URTI infections were higher in those with lower vitamin D status, with the association being stronger in those with respiratory diseases such as asthma and chronic obstructive pulmonary disease. Vitamin D is essential for good health, especially bone and muscle health. Many people have low blood levels of vitamin D, especially in winter or if confined indoors, because summer sunshine is the main source of vitamin D for most people. Matt Ridley points out in the Spectator (May 18, 2020) that the safe level of vitamin D is generally agreed to be above 10 nanograms per millilitre, but a recent study of South Asians living in Manchester found average levels of 5.8 in winter and 9 in summer: too low at all times of the year. Darker skin reduces the impact of sunlight; so does the cultural habit of veiling; and so does a reluctance among some Muslims to take supplements that might have pork-derived gelatin in them.

 

How Covid19 comes into the story

 

Many people, particularly those living in northern latitudes (including the UK, and several other Northern countries, have poor vitamin D status, especially in winter or if confined indoors. Low vitamin D status may be exacerbated during this COVID-19 crisis (eg, due to indoor living and hence reduced sun exposure), and anyone who is self-isolating with limited access to sunlight is advised to take a vitamin D orally. Matt Ridley has also argued (ibid) that an elderly, overweight, dark-skinned person living in the north of England, in March, and sheltering indoors most of the time is almost certain to be significantly vitamin D deficient. He points out that vitamin D deficiency may or may not help to prevent you catching the virus, but it does affect whether you get very ill from it.

 

 

COVID-19 is more prevalent among African-Americans, persons living in northern cities in the late winter, older adults, nursing home residents and health care workers, populations which all have increased risk of vitamin D deficiency.

 

Supplementation with vitamin D according to Government guidelines (eg, 400 IU/day (10 μg/day) for the UK  (15 – 20 μg/day  for US and Europe) has an important interaction with the colour of your skin:

 

White skin:

10 minute exposure at lunchtime, minimal clothing above waist, and no sunscreen. This will not cause sunburn.

Light brown skin:

25 minutes, as above

Dark brown/Black skin:

In the UK, sunlight on its own will not be sufficient, oral therapy will be needed in addition. The authors strongly caution against “mega doses” of Vitamin D ¹.

 

This seems to be a possible mechanism to the increased probability of death in people with darker skin colour.

 

Melzer and his colleagues studied over 4,000 patients who were tested for Covid-19, about 500 of them had had a vitamin D level done in the previous year. Of these, vitamin D status was deficient in 25%, uncertain for 16%, but sufficient for 58% ².  

 

Non-white race and being likely vitamin D deficient were associated, with a Relative Risk (RR=2.54, p<0.01). COVID-19 rates were higher in the vitamin D deficient group of 21.6%, versus 12.2% in the vitamin D sufficient group.

 

References

1. Lanham-New SA, Webb AR, et al., Vitamin D and COVID-19 disease. BMJ Nutrition, 20.04.2020)

2. Meltzer DO, Thomas J. Best TJ, et al  Association of Vitamin D Deficiency and Treatment with COVID-19 Incidence. .https://doi.org/10.1101/2020.05.08.200958

 

Stop press:  Here are two slides, the first of Covid Cases, the second of Covid deaths, dated 29^th May, 2020; from the FT. It can be seen that Covid19 cases in Sweden are at present intermediate between the UK and the US, and both Brazil and Peru are higher than either the US or the UK. Both of them are destined to go even higher. Everything now depends on whether the USA or the UK have huge secondary upswings as lockdown is released in both countries. If they do, the Swedes will smile. The deaths slide shows Brazil & Peru now not only much worse than us, but a little worse than the USA. They are certain to get much worse, as the virus sweeps through their poor and overcrowded populations.

 

 Figure 1  Covid-19 cases 

Figure 2. Covid-19 deaths

 

How the world is coping with all this

 

In my view, we should not have started removing the lockdown now: it is too early, and as my mother would have said “this will end in tears”.

Why did Boris do it? Because he wanted to distract us all at a critical time when he was at risk of losing Dom. Brazil is certain to provoke another lockdown there, and so probably will the United States, taking Mr Trump with them. And probably, I am afraid, so will we.

 

David Goldberg

29^th May 2020

77 days served; Lockdown stretching endlessly into the future for oldies.