Let’s talk about Vitamin D and COVID-19
Of all vitamins, vitamin D is perhaps the one we have seen more often in the news headlines lately.
In the UK 16-24%¹ of adults and elderly (65 years and over) are vitamin D deficient (their level of 25OHD is below 25nmol/L²) and this percentage goes up to 29.3% of the elderly during winter¹. Here at Nutrition Rocks we believe that understanding the evidence behind the words is essential to make informed choices for our health. So, we have prepared this article to burst the myths about vitamin D and, hopefully, clear up your doubts.
What is Vitamin D?
We often consider it a vitamin, but it is actually a pro-hormone². When our skin is exposed to sunlight, it absorbs UVB rays and produces vitamin D³. As highlighted in the Scientific Advisory Committee on Nutrition (SACN⁴), we need vitamin D for bone (and teeth) health, muscle strength and function.
Vitamin D deficiency is a risk factor for retarded growth (rickets⁵) in children and faulty bones (osteomalacia⁶) in adults.
Where do we find vitamin D?
Our body can source vitamin D from the sun and from food. Small quantities of vitamin D can be found in food (e.g. UV light-exposed mushrooms⁷, oily fish, eggs and fortified foods, such as some breakfast cereals⁸), but reaching the daily recommendation of 10 micrograms (µg)⁹ through dietary intake only can be hard¹⁰.
In summer and spring, we should be able to reach our daily need by sunshine¹¹ exposure. However, due to the latitude, we are less exposed to the sun in autumn and winter in the UK, so it is recommended to consider supplementing 10 µg/day in all children aged over 1-year-old and all adults⁹ to avoid vitamin D deficiency.
What has changed during the COVID-19 pandemic?
During the lockdown, due to the limited exposure to the sun from staying indoors, it has been recommended to consider taking a daily 10 µg vitamin d supplement during the spring and summer season⁹.
The existence of some evidence showing that vitamin D may help to prevent some respiratory conditions¹² has kicked off an interest in vitamin D to potentially help tackle COVID-19. However, after reviewing all current evidence on vitamin D preventing acute respiratory infection, the SACN¹³ concluded that there is not enough scientific evidence to support this hypothesis.
Furthermore, a review by the National Institute for Health and Care Excellence (NICE¹⁴) reported that vitamin D supplementation does not prevent or tackle COVID-19. Research in these fields is new and ongoing. More studies to assess the suitable dosage and frequency of use of vitamin D supplementation for optimum health are needed. Therefore, for the time being, we should continue to follow the current UK Government guidelines helping us to prevent vitamin D deficiency⁸.
One more aspect of vitamin D that has been discussed a lot lately is if the current recommendations also protect vulnerable groups. We have summarised the groups at higher risk of deficiency according to the current evidence:
BAME (Black, Asian and minority ethnic) population: the production of vitamin D in the skin is modulated by genetic factors¹⁵ - dark skin absorbs UVB rays less efficiently than white skin. This distinction is complex, as there are many genes controlling the pigmentation and within the BAME population there are several different skin tones¹⁵. Currently, there are not enough studies on the BAME population allowing for generalisation of the results, like in the case of the recent report by SACN¹¹.
Obese population: evidence shows that being obese is associated with lower levels of vitamin D, putting this group at a higher risk of vitamin D deficiency¹⁶,¹⁷. However, this relationship has shown to be reversible with fat loss¹⁸.
Elderly (65 and over): lifestyle factors¹⁷ (wearing more covering clothing, spending less time outdoors) may compromise UVB exposure. Biological factors¹⁷ (decreased functioning of kidneys and/or liver and decreased availability of a precursor of vitamin D) may compromise its formation and bioavailability in the body.
References:
3. https://www.mdpi.com/2072-6643/10/11/1656/htm
5. https://pubmed.ncbi.nlm.nih.gov/29397388/
6. https://pubmed.ncbi.nlm.nih.gov/29661756/
7. https://pubmed.ncbi.nlm.nih.gov/26865648/
8. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
9. https://www.nhs.uk/news/lifestyle-and-exercise/news-analysis-health-claims-about-vitamin-d-examined/
10. https://www.gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d
11. https://www.nhs.uk/live-well/healthy-body/how-to-get-vitamin-d-from-sunlight/
12. https://www.bmj.com/content/356/bmj.i6583
13. https://app.box.com/s/g0ldpth1upfd7fw763ew3aqa3c0pyvky
14. https://www.nice.org.uk/advice/es28/chapter/Advisory-statement-on-likely-place-in-therapy
15. https://nutrition.bmj.com/content/bmjnph/early/2020/05/20/bmjnph-2020-000096.full.pdf
16. https://academic.oup.com/nutritionreviews/article/76/9/678/5055156
17. https://cks.nice.org.uk/vitamin-d-deficiency-in-adults-treatment-and-prevention#!backgroundSub:1
Researched & written by: Valeria Folco (BSc Hons Nutrition)