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Vitamin D, Skin Colour & Covid-19

Vitamin D

Sunshine is the primary source of Vitamin D3 ( over 90 % ). Direct sun exposure to skin between 10 AM and 3PM produces Vitamin D3. This is not produced by sunlight through glass of a window.

Dietary Vitamin D2 can be increased through consumption of oily fish, egg yolk and fortified milk. Baking Fish preserves its Vitamin D content but frying it reduced it by over 50 %.

Vitamin D3 deficiency is usually asymptomatic. In children this can manifest as delayed walking, bow legs or recurrent infections. Adults may get aches, pains, tiredness and other non specific symptoms.

Vitamin D has several roles within the body including 

-bone and muscle strength

-reduced inflammation and optimum immune function

-reduced cardio-vascular disease 

-reduction in certain types of cancer

-reduced incidence of dementia and multiple sclerosis 


This meta-analysis showed an inverse relationship between Vitamin D levels and cognitive decline in Multiple Sclerosis levels

https://pubmed.ncbi.nlm.nih.gov/33709027/

 

Because Vitamin D exerts its effects through receptors within the nucleus of cells, it is now regarded as a type of steroid hormone, rather than a Vitamin ( which usually refers to co-factors required for cell processes )

In the UK, the prevalence of vitamin D deficiency in all adults is around 14.5%, and may be more than 30% in those over 65 years old, and as high as 94% in otherwise healthy south Asian adults. Vitamin D deficiency is three times more common in the winter and spring compared to the summer and autumn.

 

Treatment of Vitamin D deficiency or insufficiency usually includes a loading dose for about two months followed by regular oral supplementation. This is dependant upon age, concomitant medical conditions and levels at diagnosis. Medical advice should be sought for this. 

Sensible sun exposure, especially between the hours of 10 am and 3 pm, produces vitamin D in the skin that may last twice as long in the blood compared with ingested vitamin D 

Full-body sun exposure producing slight pinkness in light-skinned persons results in vitamin D production equivalent to ingesting over 10,000  IU  

Increased skin pigmentation, aging, and sunscreen use reduce the skin’s vitamin D3 production

 

Skin Colour 


 All humans were darkly pigmented about two million years ago. Our skin colour is dependent upon amount of natural sunscreen pigment melanin within it. Melanin protects the skin from sun damage which can lead to cancer. However it blocks production of Vitamin D3 through the skin.

Dark skinned individuals living away from the equator are increased risk of Vitamin D3 deficiency. Similarly light skinned individuals living near the equator at risk of increased skin damage and cancer.

 

'Cheddar Man', a Briton who lived in Britain over 10,000 years ago had dark skin, according to DNA analysis of remains. 

https://www.nytimes.com/2018/02/07/world/europe/uk-cheddar-man-skeleton-skin.html 


As explained by Dr Jeblonski of Penn State University, Darwinian evolution has led to different skin colours tones of different human populations. Over thousands of years, those populations who migrated away from the equator progressively developed 'depigmentation' of their skin in order to absorb more Vitamin D in environments with less sunshine.


https://www.psu.edu/impact/story/the-evolution-of-skin-color/index.html#start

 

Epidemiology of Vitamin D Deficiency


According to this survey on average 7.6% of day is spent outdoors.

https://www.researchgate.net/publication/252988142_The_National_Human_Activity_Pattern_Survey_NHAPS_A_Resource_for_Assessing_Exposure_to_Environmental_Pollutants

 

Skins ability to produce Vitamin D from sunlight decreases with age

https://pubmed.ncbi.nlm.nih.gov/2997282/

 

Darker skin colour increases risk of Vitamin D3 deficiency

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3093445/

 

Obseity increases risk of Vitamin D deficeincy

https://academic.oup.com/ajcn/article/72/3/690/4729361

 

High Fructose Corn Syrup reduce absorption of Vitamin D

https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0093611 

 

 

Vitamin D Deficiency and Respiratory Disease


15 year observational study of 10,000 patients: Those with higher Vitamin D had lower mortality from respiratory disease

https://www.mdpi.com/2072-6643/12/8/2488

 

Meta-analysis of 25 studies in BMJ showed that Vitamin D supplementation reduced incidence of respiratory illnesses 

https://www.bmj.com/content/356/bmj.i6583 


Study from Japan in school children demonstrated reduction in Influenza A by Vitamin D supplementation

https://pubmed.ncbi.nlm.nih.gov/20219962/

 

 

Vitamin D Deficiency & Covid19

 

In this observational study lower Vitamin D3 levels were associated with positive swab for SARS-COV2 

https://www.mdpi.com/2072-6643/12/5/1359 


Observational study of almost 200,000 patients which showed increased SARS-COV2 positivity rates associated with lower Vitamin D3 deficiency. 

https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0239252

 

In this hospital based observational study lower Vitamin D level was associated with a worse progression and also higher D Dimer levels which is a marker of blood clotting. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7456620/ 


In this pilot hospital based RCT, Calcifodiol ( a rapidly bio-available form of Vitamin D ) reduced ICU admission with Covid19. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7456194/

 

Pilot RCT showed quicker resolution and lower fibronogen levels ( marker of inflammation and clotting ) in patients given bolus doses of Vitamin D3

https://pmj.bmj.com/content/early/2020/11/12/postgradmedj-2020-139065 


 

INFORMATION & DISCLAIMER: 

I obtained my primary medical education from India and post graduate MD in Family Medicine from the United Kingdom. After working in National Health Service, England for 15 years, I moved to  Canada five years ago.  As a Family Physician, I consider my speciality as engaging patients, interpreting medical information for them, guiding them through their health journey, promoting wise health choices and encouraging early detection and management of disease. 

The information on this blog is accurate as per time of publishing. Scientific information and evidence changes dynamically and my opinions would change accordingly. 

The recommendations on this blog are not prescriptions and any patients considering these should consult with a physician to check if these are applicable to their unique situation.
 
Physician websites I commonly use for reference include 

 
Patient reference websites I commonly recommend to patients include
 

 
 
https://patient.info/

Patient confidentiality must be upheld at all times and any patients wishing to discuss specific medical scenarios on social media are requested to do so anonymously in 'third party' sense. 

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