Vitamin D, Immunity, and Covid–19

By Pamela Twum, RD, LD, MSc | August 11, 2022

Vitamin D is a necessary nutrient produced in the skin in the presence of ultraviolet rays from the sun. Apart from being a vitamin, it is also a hormone because it plays a vital role in maintaining proper metabolic processes in the body.

The primary source of vitamin D is the sun, however, it is also obtained in limited amounts from foods of animal origin such as liver, beef, veal, milk, yoghurt, salmons, sardines etc. It could also be obtained from fortified foods such as cereals and supplements. The Recommended Daily Allowance (RDA) of vitamin D is 10-20 micrograms depending on one’s age.

Vitamin D has various functions but its major role is to regulate the absorption of calcium and phosphorus which are essential for bone and muscle development. It also protects the health of the heart. Immunologically, vitamin D facilitates the normal functioning of the immune system by protecting the integrity of cells, and signaling specific cells to function as and when necessary.

Corona viruses are a large group of viruses that primarily target the human respiratory system. Infections related to corona viruses include Severe Acute Respiratory Syndrome Corona Virus -2 (SARS CoV-2), which is the causative organism of Covid-19. The most frequent mechanism of Covid-19 infection is through human-to-human transmission. Its primary route of spread is through droplets containing viral particles produced when an infected person sneezes or coughs. These droplets settle on mucous membranes in the mouth, nose, and eyes of individuals in close proximity, or contact with contaminated objects. Once the virus gains entry into an individual, it destroys their immune defenses thereby enabling the virus to multiply excessively. An individual with a strong immune system however is able to fight off the infection without experiencing severe outcomes.

Vitamin D receptors are present in many immunological cells and regulate the antifungal, antibacterial, and antiviral properties of the immune system. When an individual with sufficient amounts of vitamin D is infected with a Respiratory Tract Infection (RTI) including Covid-19, immunological activities of the vitamin are initiated and this causes the microorganisms to be destroyed. These activities also inhibit multiplication of microorganisms. An individual infected with Covid-19 experiences loads of inflammation by means of the body’s reaction to the virus. This can lead to lung damage and subsequent death. However, vitamin D suppresses that inflammatory response, reducing the risk of death in effect. Meanwhile, certain individuals have been shown to have an increased risk of reduced vitamin D levels. These include the elderly, dark-skinned people, and persons with chronic conditions like obesity and heart diseases. These individuals, when infected with Covid-19, have been shown to have more severe outcomes.

Several studies conducted on persons with low levels of vitamin D have concluded that vitamin D has a direct link with respiratory infections including Covid-19. A very recent study involving hospitalized patients infected with Covid-19 in Italy revealed that about 80% of the severely-infected patients had low levels of vitamin D. Again, among Swiss patients, lower levels of vitamin D were seen in persons who had various forms of respiratory tract infections including Covid-19, as compared to those who did not.

Laboratory studies have proven possible protective effect of vitamin D supplementation in RTIs and shown that indeed vitamin D has an overall significant protective effect. However, this protective effect was not observed in people with low levels of the vitamin. Even though studies have shown positive association between levels of vitamin D and Covid-19, there has not yet been an absolute evidence-based conclusion on its effectiveness in the management of Covid-19. However, since it has been shown to have protective effect in RTIs, it is prudent that measures be taken to meet its recommended daily intake.

High prevalence of vitamin D deficiency has been reported in countries with abundant sunlight supply year-round like Ghana. Deficiencies in these countries have been associated with poor dietary intake, skin pigmentation, and clothing. Vitamin D deficiency amid the Covid-19 pandemic puts one at a higher risk of infection. As such, engaging in daily activities that increase one’s exposure to sunlight like exercising, walking instead of driving short distances, and wearing light clothes that will enable one’s body to absorb enough of the vitamin from the sun is advisable.

It is important to choose foods high in vitamin D as mentioned above, fortified foods, along with proper dietary patterns. Supplementation could also be an advantage after careful consultation with your dietitian or physician. Consult dietitians for dietary advice.


Facebook Dietitian Google Dietitian LinkedIn Dietitian Twitter Dietitian