Role of vitamin D in COVID-19 and chronic health problems

October 19, 2020

Vitamin D is one of the four fat-soluble vitamins, viz., Vitamin A, D, E, K. Besides being an important nutrient for regulating many bodily functions, it is a hormone which our body makes. It is also known as the ‘sunshine’ vitamin because sun is the ultimate source from where we procure most of the vitamin D (apart from some foods which naturally contain some amounts of this vitamin in them, while there are some others that are fortified with vitamin D). 

It is a unique nutrient because it can be made in the skin from exposure to sunlight. When UVB (ultraviolet B) light/rays from the sun strikes our skin, it synthesizes vitamin D3 (Cholecalciferol). Most oil-rich fish such as salmon, mackerel, and herring contain vitamin D3. These can, however, not be considered as reliable sources because of two reasons, one being the insufficient amounts of vitamin D contained in them and secondly, the presence of a deadly toxin Mercury. 

(Refer to the following article to know about the dangers of mercury) 

Functions of vitamin D

Vitamin D plays a pivotal role in our body by-

  • Maintaining good bone health via calcium absorption and regulation of osteoblasts (bone forming cells)
  • Regulating secretion of some hormones- Insulin, parathyroid hormone (PTH)
  • Managing the activity of specific genes 
  • Improving immunity
  • Acting as a potent antioxidant
  • Fighting inflammation

The deficiency of this vitamin is also known to be a major player in the onset and progression of many chronic diseases as follows-

Vitamin D and Cancer

Calcitriol (1,25-dihydroxyvitamin D3), the biologically most active form of vitamin D while vitamin D receptor (VDR) is a carrier of vitamin D which helps in transport of the vitamin in our body. The anti-cancer effects of vitamin D are due to the actions of calcitriol. Studies have observed that calcitriol can arrest the growth of cancer cells and can also inhibit their spread (metastasis). Death of our functioning cells can also be prevented by the anti inflammatory activities of calcitriol (2).

Vitamin D and Cardiovascular diseases (CVDs)

Due to its antioxidative and anti inflammatory properties, vitamin D has a huge role in the prevention of CVDs,i.e., heart and related diseases. Sufficient vitamin D can reverse the atherosclerotic burden by its anticoagulant effect (helps in prevention of clots) and inhibition of  inflammatory pathways responsible for causing the disease. Additionally, sufficient vitamin D has been found particularly useful in Hypertension.

Vitamin D and Diabetes

Vitamin D receptor (VDR) has a crucial role in preserving the function of islet cells. It can  improve both insulin sensitivity and insulin synthesis and hence, low vitamin D levels have repeatedly been shown to be linked with increased risk of type 2 diabetes mellitus. It does so by inhibiting the inflammatory factors and alleviating chronic inflammation process of the pancreas to improve the function of islet β cells (β cells of islets secrete Insulin).

Vitamin D and Immune system diseases

Calcitriol along with VDR are essential for our immune system biology. Many immune cells in our body (monocytes, macrophages, dendritic cells, T cells, and B cells) work closely with VDR. This combination of VDR and the immune cells of our body can help in delaying the progress of chronic inflammatory autoimmune diseases (Autoimmune thyroid diseases- Hashimoto’s and Grave’s disease, rheumatoid arthritis, multiple sclerosis, psoriasis, type-1 diabetes, etc).

Vitamin D and COVID-19

The outbreak of COVID-19 has created a global public health crisis. Little is known about the protective factors of this infection.

One of the preventive health measures that can reduce the risk of infection, progression and severity of this deadly virus and is being increasingly postulated is supplementation of Vitamin D.

As it can profoundly improve our immune status (Vitamin D and Immune system diseases), it has been used as an adjunct treatment therapy in the reversal of COVID-19 and also other respiratory problems in the past as well (Tuberculosis, common cold, Asthma and so on).

Also it has been found, in some recent reviews, that vitamin D insufficiency/deficiency may compromise respiratory immune function, thus, increasing the risk of COVID-19 occurrence.

Vitamin D and neurological disorders

It has been well documented that D-vitamin can protect our brian nerves by its antioxidant effects, thereby significantly reducing the risk of depression, Alzheimer’s, epilepsy and neurocognitive decline. Moreover, vitamin D may also be involved in the development and function of the brain.

Vitamin D and fractures, falls

It has been found that vitamin D may increase muscle strength and can thus, prevent falls.Many studies have shown an association between low vitamin D concentrations and an increased risk of fractures and falls in older adults.

Risk factors affecting Vitamin D status in the body

  • Inadequate exposure to sunlight
  • Higher use of sunscreen with a sun protection factor (SPF) of 30
  • Natural dark skin tone
  • Obesity (BMI >30kg/m2)
  • Fat malabsorption
  • Bariatric patients
  • Nephritic syndrome/ inflammation of kidneys
  • Disorders like TB, chronic fungal infections
  • Some lymphomas
  • Old age
  • Gastric bypass surgery
  • Liver problems

Vitamin D- natural or supplementary may interact with several types of medications like- Corticosteroids 

Orlistat and Cholestyramine 

Phenobarbital and phenytoin


Medications to treat AIDS/HIV

Hence, to avoid malabsorption, these drugs are generally advised to be taken several hours apart from vitamin D supplements.

Vitamin D deficiency

In children, rickets is caused due to deficiency, wherein the bones become soft and bend. Osteomalacia is yet another problem which causes weak bones, bone pain, and muscle weakness. The outcome of D deficiency in terms of osteoporosis and increased fracture risk is well known.

One of the most serious disorders associated with vitamin D deficiency is the convulsive state of hypocalcemia tetany, which is caused by insufficient supplies of calcium to nerves and muscles.

Further, due to its long list of functionalities, vitamin D deficiency can lead to many health problems.

Vitamin D requirements

Optimal levels of vitamin D in the blood should be between 50-75 ng/ml. For most people, the best way to get enough vitamin D is taking a supplement because it is hard to eat enough through food and even sunlight exposure. Vitamin D supplements are available in two forms: vitamin D2 (“ergocalciferol” or pre-vitamin D) and vitamin D3 (“cholecalciferol”). D2 is produced in plants and fungi and D3 in animals, including humans.

So tribe, get yourself checked for your vitamin D levels today and avoid all the untimely health risks just in time. We at iThrive can help you in resolving your health issues, if you’re already dealing with any. Feel free to book a consultation today!


Ria Jain
Functional Nutritionist

Ria has a Master’s in Nutrition and Dietetics and is in a permanent research mode and keeps the rest of us at iThrive (Previously ThriveFNC) updated with her latest findings in the field of Nutrition. Her articles on iThrive's blog are an expression of her research findings. We really don’t know what we’d do without her support and her focus.

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.