Effects of Vitamin D on Risks and Severity of COVID-19 Infection

Document Type : Original Articles


1 Department of Biology, College of Education for Pure Sciences, University of Kerbala, Kerbala, Iraq

2 General Directorate of Education in Karbala


In the last two decades, numerous studies have been carried out to find correlations between vitamin D and the efficiency of the lungs and respiratory system. This study aimed to find the relationship of taking vitamin D with the risks of the severity of infection with coronavirus disease 2019 (COVID-19) and the risk of infection of patients with chronic diseases. A total of 100 COVID-19 patients (61 males and 39 females) were included in the study and divided into groups, namely never taken vitamin D and taken a dose of 50 and 1,000 IU. The effects of gender, chronic diseases (i.e., hypertension and diabetes), and requiring intensive care unit (ICU) were evaluated. The results showed that females were at lower risks of infection with COVID-19 than males and taking 50 IU of vitamin D could lower the severe cases by 33%. It was also revealed that patients with chronic disease were more sensitive to COVID-19 and administering 50 units of vitamin D in these patients decreased the need for ICU from 49% to 9%. Given that vitamin D enhances the immune system and respiratory function, the findings of this research indicated that vitamin D reduced the risk of COVID-19; however, it was not able to prevent it.


Main Subjects

1. Introduction

Vitamin D is a cyclic hydrocarbon compound called prohormones. It is the fat-soluble substance that has an important role in bone health due to its main part in absorbing phosphorous, calcium, and magnesium and controlling the functions of the cellular cells. It also has highly considerable properties that enhance the immune system, such as neuroprotective, antioxidant, and anti-inflammatory. Vitamin D can control the expression of the genes and support the activities of the brain cells and the functions of the muscles. This vitamin is obtained from sun exposure, foods (e.g., eggs), fatty fish (e.g., salmon), fortified cereal, fortified milk, and other resources ( 1 , 2 ). The human body is capable of synthesizing vitamin D through the reaction between skin and sunlight; nevertheless, the result of this process is affected by numerous factors, such as exposure time to sunlight, pigment on skin, latitude, and season ( 3 , 4 ). The findings of numerous researches have exhibited a possible link between vitamin D deficiency and different diseases, including systemic infections ( 5 ).Vitamin D is involved in activating immune systems and deficiency of this affected immune function ( 6 ). The proper concentration of vitamin D increased innate immunity by separating anti-viral peptides ( 7 ), improved the mucosal defenses. In the clinical studies, reduced vitamin D levels in the blood had been related to acute respiratory infections, which include pandemic influenza ( 8 ). Some recent studies had hypothesized that deficiency in vitamin D might lead to respiratory and immunity failure and an increased risk and severity of coronavirus disease 2019 (COVID-19) infection and mortality in patients ( 9 ). In 2011, it was shown that vitamin D directly affected lung function by increasing the secretion of cathelicidin (an antimicrobial peptide), reducing chemokine production, leading to the activity of T cells, and inhibiting the activity of dendritic cells ( 10 ). Vitamin D deficiency affects respiratory diseases and increases the infection with mycobacteria. However, it has been noticed that increasing vitamin D levels in the blood can lead to recovery from asthma ( 11 , 12 ). Recent data have suggested the antiviral effects of vitamin D may directly inhibit virus replication and has anti-inflammatory responses ( 13 ). During the COVID-19 pandemic, a lot of pieces of research and studies were carried out to find the correlation between the coronavirus infection and vitamins ( 14 , 15 ). The results of the research have shown that although vitamin D cannot prevent COVID-19 infection, it can reduce the disease severity and mortality (15, 16). The findings of a number of recent reviews have found some of the pathways through which vitamin D reduces the risk of microbial infection ( 17 ). Vitamin D follows a variety of mechanisms to decrease viral infections and mortality. For the purpose of reducing the risks of respiratory infection, vitamin D utilizes three pathways, namely physical barrier, natural cellular immunity, and adaptive immunity ( 18 ). The outbreak and rapid spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus is a global health threat with unstable outcomes all over the world. The current study was carried to find the relationship between the severity of infection with COVID-19 and the level of vitamin D in the blood and compare it with the control group.

2. Materials and Methods

The statistical sample of this study included 100 (61 males and 39 females) COVID-19 patients that their infection was confirmed by a specialist physician using a computed tomography scan or positive reverse transcription polymerase chain reaction test for SARS-CoV-2. Informed consent was obtained from patients to enter the study. The patients were divided into two groups, including those who never took vitamin D and those that received vitamin D (50-1000 IU). The effect of the gender and chronic diseases, such as hypertension and diabetes, for which patients needed care at intensive care unit (ICU), were also evaluated. Patients' clinical symptoms and conditions during the infection, such as headache, diarrhea, shortness of breath, and loss of sense of smell and taste, were measured and recorded.

2.1. Statistical Analysis 

All the collected data were statistically analyzed in SAS software 2012 ( 19 ). Statistical tests were analyzed by ANOVA, t-test, and Chi-square. A p-value of less than 0.05 was considered significant.

3. Results and Discussion

This study was conducted to evaluate the role of vitamin D in patients with COVID-19. Patients were classified according to gender, and a dosage of vitamin D was given to them according to table 1. It was revealed that the number of infected cases was much higher in pertains who never took a dose of vitamin D; however, it could not protect the patient from infection, which was consistent with the results of other studies ( 11 , 14 ).

Gender Number and percentage Never take Vitamin D Dose 50 IU Dose 1,000 IU Total P-value
Males Number 34 5 22 61 0.105
Horizontal percentage 55.7% 8.2% 36.1% 100%
Vertical percentage 66.7% 35.7% 62.9% 61.0%
Females Number 17 9 13 39
Horizontal percentage 43.6% 23.1% 33.3% 100%
Vertical percentage 33.3% 64.3% 37.1% 39.0%
Table 1. Effects of vitamin D intake on infection with COVID-19 and its comparison with control for males and females

Based on the data in table 2, chronic diseases could increase the possibility of infection with COVID-19. The results of a study conducted by Liu ( 20 ) showed that chronic diseases affected the severity and mortality of COVID-19.

Gender Number and percentage Nonchronic disease Hypertension Diabetes Hypertension and diabetes Total P-value
Males Number 55 1 1 4 61 0.940
Horizontal percentage 90.2% 1.6% 1.6% 6.6% 100%
Vertical percentage 62.5% 50.0% 25.0% 66.7% 61.0%
Females Number 33 1 3 2 39
Horizontal percentage 84.6% 2.6% 7.7% 5.1% 100%
Vertical percentage 37.5% 50.0% 75.0% 33.3% 39.0%
Table 2. Effect of chronic diseases on infection with COVID-19 in males and females

According to table 2, the number of non-infected people with coronavirus is much higher in those who never had any chronic diseases. This number is higher in those with both hypertension and diabetes than in those with only one of them.

Table 3 presents a comparison between males and females regarding the severity of the infection with coronavirus.

Gender Number and percentage Severe infection Moderate infection Light infection Total P-value
Males Number 14 28 19 61 0.310
Horizontal percentage 23% 45.9% 31.1% 100%
Vertical percentage 73.7% 62.2% 52.8% 61.0%
Females Number 5 17 17 39
Horizontal percentage 12.7% 43.6% 43.6% 100%
Vertical percentage 26.3% 37.8% 47.2% 39.0%
Table 3. Effect of gender on the severity of infection with COVID-19

According to table 3, the percentage of severe infections is double in men, while it is almost equal in moderate infections, and for mild infections, the percentage is higher in women than in men, which is consistent with the results of a study conducted by Jin, Bai ( 21 ). 

Table 4 shows a comparison between male and female patients who needed ICU, indicating that male cases needed ICU more than their female counterparts (14.8% vs. 10.3%, respectively); this percentage may vary depending on the place and country.

Gender Number and percentage Does not need ICU Need ICU Total P-value
Males Number 52 9 61 0.510
Horizontal percentage 85.2% 14.8% 100%
Vertical percentage 59.8% 69.2% 61.0%
Females Number 35 4 39
Horizontal percentage 89.7% 10.3% 100%
Vertical percentage 40.2% 30.8% 39.0%
Table 4. Effect of the severity of the infection with COVID-19 on the need for ICU in male and female patients

The results of this study demonstrated that vitamin D administration could reduce the risk of coronavirus in patients suffering from chronic diseases, such as hypertension and diabetes.

According to table 5 and the findings of other studies, vitamin D could reduce the severity of the infection with COVID-19 ( 22 , 23 ). The severe cases were decreased by 33% in those who took 50 IU of vitamin D (Table 6).

Dose Number and percentage Without chronic disease Hypertension Diabetes Hypertension and diabetes Total P-value
Never take vitamin D Number 46 1 20 2 51 0.900
Horizontal percentage 90.2% 2.0% 3.9% 3.9% 100%
Vertical percentage 52.3% 50.0% 50.0% 33.3% 51.0%
50 unit Number 13 0 0 1 14
Horizontal percentage 92.9% 0.0% 0.0% 7.1% 100%
Vertical percentage 14.8% 0.0% 0.0% 16.7% 14.0%
1,000 unit Number 29 1 2 3 35
Horizontal percentage 82.9% 2.9% 5.7% 8.6% 100.0%
Vertical percentage 33.0% 50.0% 50.0% 50.0% 35.0%
Table 5. Effects of vitamin D dose on individuals with chronic diseases and COVID-19
Dose Number and percentage Severe infection Moderate infection Light infection Total P-value
Never take vitamin D Number 6 22 23 51 0.170
Horizontal percentage 11.8% 43.1% 45.1% 100%
Vertical percentage 31.6% 48.9% 63.9% 51.0%
50 IU Number 4 5 5 14
Horizontal percentage 28.6% 35.7% 35.7% 100%
Vertical percentage 21.1% 11.1% 13.9% 14.0%
1,000 IU Number 9 18 8 35
Horizontal percentage 25.7% 51.4% 22.9% 100.0%
Vertical percentage 47.4% 40.0% 22.2% 35.0%
Table 6. Effects of vitamin D dose and severity of infection by COVID-19

In table 7, a significant correlation was found between patients who needed ICU and vitamin D uptake (P=0.01). The percentage of patients in need of ICU dropped from 49% for patients who had never taken a dose of vitamin D to 9% for patients who received 50 IU for vitamin D, these findings were in agreement with those of other studies ( 24 - 26 ).

Dose Number and percentage Need ICU Not need ICU Total P-value
Never take vitamin D Number 49 2 51 0.01
Horizontal percentage 96.1% 3.9% 100%
Vertical percentage 56.3% 15.4% 51.0%
50 IU Number 9 5 14
Horizontal percentage 64.3% 35.7% 100%
Vertical percentage 10.3% 38.5% 14.0%
1000 IU Number 29 6 35
Horizontal percentage 82.9% 17.1% 100.0%
Vertical percentage 33.3% 46.2% 35.0%
Table 7. Effect of vitamin D dose and the need to ICU for people with COVID-19

It is important to note here that the effectiveness and value of vitamin D, as a supplement in the treatment of coronavirus, are unclear and there is no understandable explanation for its mechanism in vivo condition. However, the results of a study conducted by Murai, Fernandes ( 27 ) revealed that increasing vitamin D intake would not affect the length of staying in the hospital. The study eventually did not encourage raising vitamin D dose to supplement the treatment of coronavirus patients. The same finding was confirmed in a study carried out by Hernandez, Nan ( 28 ) reporting that there was no relation between the dosage of vitamin D and recovery from the COVID-19 virus.

The results of the present study indicated that females were at lower risks of infection with COVID-19 than males, and taking 50 IU of vitamin D could reduce the severe cases by 33% and the need for ICU from 49% to 9%. It was also found that vitamin D enhanced the immunity and respiratory systems, and although it lowered the risks of infection with COVID-19, it was not able to prevent it. Patients with chronic diseases were more susceptible to the coronavirus than others. On the other hand, the findings of a study demonstrated that maintaining a level of vitamin D could participate in coping with the COVID-19 virus pandemic ( 29 ). However, it is important to consider other factors, such as chronic diseases, environment, and genetic history of the patients.

Authors' Contribution

Study concept and design: H. A. R. A.

Acquisition of data: B. S. A. A.

Analysis and interpretation of data: H. A. R. A.

Drafting of the manuscript: B. S. A. A.

Critical revision of the manuscript for important intellectual content: H. A. R. A.

Statistical analysis: B. S. A. A.

Administrative, technical, and material support: H. A. R. A.


The study protocol was approved by the Ethics Committee of the University of Kerbala, Iraq.

Conflict of Interest

The authors declare that they have no conflict of interest.


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