Vitamin D, also known as calciferol, is a naturally occurring vitamin in our body. It is a fat-soluble vitamin and exists in multiple forms. In food and dietary supplements, it naturally exists in 2 forms: Vitamin D2 (Ergocalciferol) and Vitamin D3 (Colecalciferol). Vitamin D is also produced within the body when it is exposed to UV rays. It will then undergo a two-stage activation in the body, first by the liver, then by the kidneys.
Deficiency in vitamin D can lead to several diseases, such as a loss of bone density (and eventually leading to osteoporosis and easily broken bones). In children, severe vitamin D deficiency can lead to a disease called rickets. In adults, this can lead to a condition called osteomalacia, where the bones become soft and may experience bone pain[2,3].
Other than its effect on the bones, there are also growing evidence with respect to vitamin D’s role in boosting a person’s immunity, which is especially important in this COVID-19 pandemic climate. Read on to find out more about the different functions of vitamin D.
In previous studies, vitamin D has been shown to be able to modulate the immunity responses in our body. There are also reports and studies to show an association between low levels of vitamin D and higher incidences of upper respiratory tract infections (URTI). Also, there has been increasing evidence linking vitamin D deficiency with autoimmune diseases, such as rheumatoid arthritis (RA) and inflammatory bowel diseases (IBD). These effects could be thought to be due to the immune cells being able to respond to vitamin D in the presence of vitamin D receptors on them.
Vitamin D and COVID-19
COVID-19 pandemic has plagued the world for more than 2 years, starting from early 2020. There are more than 400 million people worldwide that has been infected with COVID-19, resulting in more than 6 million deaths. There have been several suggestions on how vitamin D could be used as a supplement to help combat COVID-19 infection by boosting the immune system.
A sufficient level of vitamin D in the body is reported to be able to lessen the effects on increased inflammatory markers and cytokine storm in COVID-19 infection, and that vitamin D deficiency could be associated with a more severe COVID-19 infection, including mortality.
A study was conducted in 2021 September, where investigators collated and analyze 21 trials that looked at the association between vitamin D and COVID-19 infection. The authors concluded that a low level of vitamin D may have the potential to increase the risk of COVID-19 infection and severe disease. They have also suggested to add vitamin D supplementation to COVID-19 prevention and treatment protocols.
Similar studies have also been carried out to study the association between vitamin D levels and COVID-19 infection. Chiodini I et al. also performed a systematic review of 54 studies and found that low levels of vitamin D were associated with ICU admissions, mortality, hospitalizations, and infection rate of COVID-19. Dror A et al. also studied Israel registries of patients that had COVID-19 infections and found that lower levels of vitamin D were more common in patients with severe or critical disease.
Traditionally, Vitamin D has also been known to be beneficial for bone health. Vitamin D increases absorption of calcium and maintains normal levels of calcium and phosphate. This helps keep the bones strong and avoid complications such as osteoporosis and osteomalacia. Research has shown that low levels of vitamin D intakes over a long period of time can lead to demineralization of the bones.
Vitamin D increases the absorption of calcium, and this feedback will decrease the breakdown of the bones by the body (to maintain sufficient calcium levels) . Therefore, it is important to have sufficient intake of vitamin D to prevent and minimize risk of fractures, especially when you age.
Apart from its benefits for immune and bone health, vitamin D also has been found to help in combination with topical minoxidil for female-pattern hair loss, as discovered in a recent study by Hassan G et al. It was found that treatment with a combination of both oral vitamin D and topical minoxidil had better outcomes for female pattern hair loss as compared to either treatment options alone. Low levels of vitamin D has also been found to be associated with several diseases such as multiple sclerosis (an autoimmune disease), and heart diseases.
The main indicator of vitamin D levels in your body is by taking the blood levels. The Endocrine Society recommends that adults need at least 37.5mcg to 50mcg of vitamin D to maintain an adequate level of vitamin D in the body (i.e., serum vitamin D of > 30ng/mL), which is the level generally considered to be sufficient for bone and overall health in healthy adults and individuals. However, it is also noted that a level of more than 50 ng/mL may be considered as harmful and is associated with adverse effects[18,19].
Some natural and dietary sources of vitamin D include cod liver oil, flesh of fatty fish (e.g., salmon, tuna), mushrooms, and certain types of red meat. Also, although having sufficient sunlight is important in the production on vitamin D in your body, it is also critical to understand that overexposure may lead to detrimental effects like skin cancer as well.
Traditionally, vitamin D has been viewed as an important vitamin in the regulation and maintenance of bone health. Recent studies have also pointed vitamin D to be an important vitamin in boosting our bodies’ immune system. This finding may be valuable especially in this COVID-19 pandemic, with evidence to show that a sufficient level of vitamin D may be crucial in preventing severe disease of COVID-19 infection as well.