Israeli scientists concluded in a recent study, that there were “striking” differences in the likelihood of contracting severe COVID-19 illness, between individuals who had sufficient levels of vitamin D prior to catching the virus, and those who did not.
Life-threatening levels of severity of illness were seen in about half of the people with insufficient circulating vitamin D levels, compared with less than 10 % of people with "normal" levels.
Importantly, this study had recorded the vitamin D levels from subjects before they contracted COVID, which enabled the effect of differing vitamin D levels to be recorded.
“We found it remarkable, and striking to see the difference in the chances of becoming a severe patient when you are lacking in vitamin D compared to when you’re not.” A lead author commented.
The study included 253 people, admitted to a hospital between April 7, 2020 and February 4, 2021 when the Delta variant was prominent.
The study authors, however, explained that the results would be “equally relevant” for the Omicron variant.
Many in the medical community believe that adequate vitamin D levels should be circa 20 ng/mL, but many experts believe these levels are very low.
In fact, guidance on sufficient vitamin D levels have historically been targeted at a level just above that to prevent a condition known as rickets, where a lack of vitamin D and subsequent calcium utilisation, results in soft and deformed bone structure.
In truth, evolutionarily, healthy humans would have experienced sun exposure to maintain a healthy 50-60 ng/mL of circulating vitamin D.
Direct exposure to UV-B sunlight, is the main source of vitamin D for humans, although we can obtain a small amount in food.
Many factors prevent us from achieving adequate levels in our modern society.
Dark skinned people, who have developed skin pigmentation to tolerate strong sunlight and long days in equatorial climates, filtering just enough vitamin D to be healthy, may choose to live in the northern or southern hemisphere, and become deficient.
Conversely, many people who have lighter skin, designed to optimise the absorption of UV-B in an environment where there is little strong sunlight, may decide to live in an equatorial climate with greater sunlight and sun intensity, but become fearful of over-exposure and use very high SPF suncream to avoid skin damage.
Both of these groups have a significant risk that they do not achieve the levels of sun exposure necessary for good health.
Additionally, many people in the developed world work indoors, wear long-sleeved shirts and long trousers, apply suncream or moisturiser with a high SPF and don't expose ourselves to direct sunlight.
We are told that too much sun can be harmful, but we have in fact created more harm through a lack of sun exposure.
These factors, and many others, contribute to a general level of circulating vitamin D for most in the developed world, which is way too low for good health.
Vitamin D is fat soluble, and can be found in foods such as fatty fish, egg yolks and mushrooms, but the quantities available in food are so low, that from a practical standpoint, if you are deficient, then sun exposure and supplementation are likely to be essential.
Professor Wright explains that low vitamin D level "is surely a primary cause of severe COVID-19" and that "supplements" are the most practical route to resolve a deficiency.
(Chauss, D. et al. Autocrine vitamin D signalling switches off pro-inflammatory programs of TH1 cells. Nature Immunol 23, 62–74 (2022)). Link to study here.
Vitamin D plays a pivotal role in reducing the risk of respiratory and other infections, helping healthy bone development and many other positive genetic expressions within our bodies.