Updated: Jul 16
What is Vitamin D?
Vitamin D is a fat soluble vitamin produced due to the action of sunlight (UVB radiation). It plays a critical role in the prevention of bone fractures and promotes calcium and phosphorus absorption from the intestinal tract. In addition to being involved in bone health, it fulfils an important function within the immune system, impacting susceptibility to infection, especially in the prevention of acute respiratory tract infections. Several studies have already highlighted the inverse association between vitamin D levels with severity and mortality of respiratory viral infections in both children and adults. (Teymoori-Rad et al, 2019). Experiments on different Vitamin D levels has shown vitamin D to affect brain cell differentiation and the expression of proteins involved in neuronal makeup in the brain.
Having such an essential role in our health, it is alarming to know that vitamin D deficiency, known as hypovitaminosis D, is a global concern which has seen a targeted global public health response. It is thought to affect more than one billion people world wide. Due to work patterns, shift workers are found to be at a higher risk of hypovitaminosis D, reaching up to a suggested 80% prevalence; as found in a systematic review of research conducted by Sowah et al (2017). This message is highlighted in a soon to be published paper by deMenezes Jnr et al (May 2021), which studies the link between vitamin D deficiency and sleep disorders in alternating shift patterns. Hypovitaminosis D is a highly spread condition correlated with increased risk of respiratory tract infections and hence the indicated link to COVID -19 severity and outcome.
Factors that impact our risk of Vitamin D deficiency
Understanding how we obtain vitamin D helps understand this problem better. Our key way of getting vitamin D is through exposure to sunlight. However, there are many factors that impact our level of exposure to sunlight and resulting level of circulating vitamin D. On this list is: reduced outdoor activity, shift work patterns, seasonal variance, medication usage, age, thyroid dysfunction, pregnancy, and obesity. Genetic predispositions, skin type (pigmentation), health, season latitude, clothing and nutrition are also among the long list of factors that can impact vitamin D levels. At higher latitudes people with more melanin content in their skin have lower blood levels of vitamin D because their skin does not produce as much in response to sunlight. An analysis of data from 4962 participants in the national health and nutrition examination survey in the US found that 1981 (39.92%) were vitamin D deficient, defined as a blood level lower than 20 ng/mL.
What is the natural content of Vitamin D in our food?
Most people get some vitamin D from sunlight exposure, although more individuals are now getting their main source of vitamin D from fortified foods such as milk, orange juice and breakfast cereals. The level of vitamin D in meat, eggs and milk depends on access to sunlight and ultraviolet B (UVB) light, as well as the amount of Vitamin D in the feed and the food’s fat content. The time of year of food provision to the market also has an influence, with summer yielding higher levels.
What is the link to COVID-19?
In a retrospective study, Caragnano et al (2021) analysed vitamin D levels in patients with acute
respiratory failure due to COVID-19 with the aim of assessing any potential correlations with COVID-19 severity and prognosis. Of the 42 patients in the study, 81% of the patients had hypovitaminosis D based on vitamin D levels. This aligns to other studies which have found a high prevalence of hypovitaminosis D in COVID-19 patients; with severe vitamin D deficiency having a significantly higher mortality risk.
We have already alluded to the seasonality of vitamin D and such seasonal COVID-19 patterns are yet to be determined. Studies in this area although informative need long-term study approaches. D’Avolio et al (2020) reported a lower level of vitamin D (in its form of 25-hydroxyvitamin D (25(OH)D) in COVID-19 patients with positive PCR compared to patients with a negative PCR. Furthermore, serum level of 25(OH)D was lowest in critical cases but highest in mild cases.
The complex interplay between COVID-19 infection and vitamin D remains a research topic of interest especially given our understanding of Vitamin D deficiency’s association with respiratory conditions and the widespread availability of vitamin D supplementation. The idea of supplementing vitamin D as a preventive measure, and a potential treatment, in the battle against COVID-19 has already attracted many research trials. Evidence presented in one such study by Teymoori-Rad et al (2020) suggests that vitamin D supplementation could potentially be effective either in the treatment or prevention of COVID-19.
What role could Vitamin D play in COVID-19 prevention/treatment?
Through a number of different mechanisms, Vitamin D appears to induce defensive antimicrobial responses and minimises the pro-inflammatory responses in patients. In COVID it is the bodies uncontrolled immune response (or cytokine storm) which can lead to acute respiratory status. Therefore, vitamin D can be seen as an immune modulating agent. This is what vitamin D has long been known to do in non-COVID-19 respiratory viral infection studies. The exact means by which vitamin D balances inflammation and the bodies antiviral state has yet to be fully understood.
Where can a shift worker get vitamin D from?
As the key means of obtaining a healthy level of vitamin D is via exposure to sunlight, accessing enough vitamin D has always proved challenging for shift workers; especially those on rotating
shift patterns. Diet is the next best turn to for shift workers through the consumption of fortified milk and natural products such as fish, eggs and mushrooms. For those with busy lives or
even those who want the reassurance they are getting the necessary level of vitamin D, there are food supplements. A supplement of the recommended dietary allowance (RDA) of 600-1000 IU per day is suggested to provide a level of assurance.
What have studies said about the use of Vitamin D supplement and COVID?
One of the first prospective studies to date on vitamin D supplementation was recently published in the American Journal of Clinical Nutritional Science. Hao Ma et al ( 2021) conducted a study of 8,297 adults who had records in the UK Biobank (from 16th March 2020 to 29th June 2020). The UK Biobank is a large, population based cohort study comprising more than half a million participants aged between 37 -73 years living in the UK. It holds genetic data for approx. 7549 people. Genetically predicted vitamin D levels were evaluated by a genetic risk score. The researchers specifically explored the use of vitamin D supplements, the amount of circulating vitamin D and other main covariates compared against an already recorded baseline (2006-2010) of the study participants.
The habitual use of vitamin D supplements was significantly associated with a 34% lower risk of COVID-19 infection.
Circulating vitamin D levels at baseline or genetically predicted vitamin D levels were not associated with lower risk of COVID-19 infection.
A number of potential mechanisms have been proposed to explain the observed inverse relationship between habitual use of vitamin D supplements and the risk of COVID -19 infection. Many of these centre on how the virus operates and how the body reacts to the virus. As shown in figure 1, above, Vitamin D supplementation is proposed to take on preventative and therapeutic roles depending on the life cycle stage of the COVID-19 virus. Initially vitamin D is understood to act as a general inhibitor of viral infection in the human body. Once the virus starts to take hold (infection has started) vitamin D is seen to modulate infection via interaction with both cells and virus factors. Such an initial viral infection can cause stress at a cellular level known as ER stress. The body’s immune system kicks in and responds to the infection in a bid to eliminate it or at least keep it at bay. This is a critical stage in the bodies response to the virus. Vitamin D is associated with both innate and adaptive immune responses and may aid more efficacy in the body’s immune response against the virus. If this immune response does not keep the infection at bay there is a risk of the body entering a phase of uncontrolled immune response which is associated with severity and fatality in COVID-19. This alone would present a strong case for taking a vitamin D supplement on a longer term basis.
Bio-Thrive’s Shift Worker Total Health™ Food Supplement contains 25 µg of vitamin D (equating to 500% the RDA) along with a unique to market combination of natural vitamins, minerals, amino acids, plant extracts, alpha lipoic acid, coconut oil, omega oils (fish oil microencapsulated), co-enzyme Q10, lemon and apple pectin and live cultures/bacteria.
Carpagnano, G.E., Di Lecce, V., Quaranta, V.N., Zito, A., Buonamico, E., Capozza, E., Palumbo, A., Di Gioia, G., Valerio, V.N and Resta, O. (2021). Vitamin D deficiency as a predictor of poor prognosis in patients with acute respiratory failure due to COVID-19.
Journal of Endocrinological Investigation 44:765-771.
D’Avolio, A., Avataneo, V., Manca., A et al. 25 -hydroxyvitamin D concentrations are lower in patients with positive PCR for SARS-CoV-2.
Nutrients, 12(5). 1359.
De Menenzes Junior, L.A, Fajardo, V.C., de Freitas, S.N., Pimena, F.A., de Oliveira, F., Machado-Coelho, G., do Nascimento Neto, R., and Meireles, A.L. (2021) pre-print (10th May 2021). Hypovitaminosis D is associated with sleep disorders in workers on alternating shifts with cardiovascular risk factors.
Eyles, A.W. (2021). Vitamin D: Brain and Behaviour.
JBMR Plus Vol 5, No.1, e10419.
Hao Ma, Tao Zhoum, Yoriko Heianza and Lu Qi (2021). Habitual use of vitamin D supplements and risk of coronavirus disease 2019 (COVID-19) infection: a prospective study in UK Biobank.
American Journal of Clinical Nutrition. 113: 1275-1281.
Jakobson, J. & Christensen, T. (2020). Natural vitamin D in food: to what degree does 25-Hydroxyvitamin D contribute to the vitamin D activity in food?
JBMR Plus Vol.5, No.1.
Sowah, D, Fan, X., Dennett, L. Hagtvedt, R., Straube, S. (2017). Vitamin D levels and deficiency with different occupations: a systematic review.
BMC Public Health (e-pub: http://ncbi.nlm.nih.gov/pubmed/28637448)
Teymoori-Rad, M. (2021). Vitamin D and COVID-19: From potential therapeutic effects to unanswered questions. Review in Medical Virology. 31: e2159.
Teymoori-Rad, M., Shokri, F., Salimi, V., Marashi, S.M. (2019). The interplay between vitamin D and viral infections. Review in Medical Virology.