European Journal of Integrative Medicine 60 (2023) 102249

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Research paper

Dietary supplements used by otolaryngology patients in Turkey during the

COVID-19 pandemic: A cross-sectional survey
Mehtap Koparal a, Miray Ege b,*
a
Department of Otolaryngology, Faculty of Medicine, Adiyaman University, Adiyaman, Turkey
b
Department of Pharmacognosy, Faculty of Pharmacy, Adiyaman University, Adiyaman, Turkey

A R T I C L E I N F O
A B S T R A C T
Keywords:
Introduction: This study investigated the characteristics of dietary supplement (DS) use of patients who attended
COVID-19
the otolaryngology clinic at a university training and research hospital in Turkey during the pandemic, including
Dietary supplements
Food supplements patients who had experienced Coronavirus disease 2019 (COVID-19).
Diseases Methods: This cross-sectional study was conducted between March and September 2021. 277 literate patients
Protective treatment aged ≥ 18 years who attended the otolaryngology clinic were enrolled. A questionnaire was used to collect
sociodemographic data, as well as data on DS use during the pandemic. The questionnaire was administered in a
face-to-face setting by a single researcher.
Results: Approximately half of the participants (50.18%) took DSs during the pandemic and 67.18% of those who
experienced COVID-19 infection used DSs during their illness. The most commonly used supplements were
vitamin C (43.16%) and D (33.09%), along with herbal supplements such as lemon (54.68%), garlic (46.76%),
ginger (46.04%), and thyme (43.88%). In total, 85.23% of the patients primarily used DSs to enhance their
immunity, while 32.95% used them to prevent cough, and 26.14% to improve breathing. The majority of the
patients (85.23%) felt benefit from DSs. Typically, the patients obtained information about DSs from doctors
(32.37%) or friends and relatives (29.49%), and most of them used the supplements without first consulting a
doctor (63.64%).
Conclusion: DSs were commonly used by otolaryngology patients during the COVID-19 pandemic, particularly to
enhance immunity. Although the majority of patients reportedly benefited from these products, most of them did
not inform their physicians that they were using them and often obtained information from unofficial sources.

1. Introduction
and family medicine units, 14-day quarantine periods were imple-
mented, and at-risk individuals were followed up [4].
Coronavirus disease 2019 (COVID-19) emerged in Wuhan (China) in
Similar to most other countries, protective measures introduced in
December 2019 and subsequently spread worldwide [1,2]. A global
Turkey to prevent the spread of COVID-19 included facemask use,
pandemic was declared on 11 March 2020 by the World Health Orga-
reg- ular hand sanitization, avoidance of social contact where possible,
nization (WHO) [3]. Measures to reduce transmission were imple-
contact tracing, and quarantine [5]. Because the pandemic poses a
mented by the Turkish government in accordance with the
threat to global health, pharmacological treatments and vaccines were
recommendations of the WHO. The COVID-19 Scientific Committee
developed. However, the rapid development of new therapeutics is
in Turkey produced the “COVID-19 Disease Guide,” which provides
hampered by strict regulatory processes associated with the need to
gen- eral information about isolation and infection control, as well as
fully understand the pathophysiology of the target disease [6]. In
patient care and treatment. This guide advocates a standardised
addition, novel treatments can be anxiety-provoking for patients given
approach to the management of suspected cases. Strict procedures
the pos- sibility of side effects. Therefore, many people favor natural
were applied in Turkey for detected cases; close contacts were
treatment options and dietary supplements (DSs) to strengthen
monitored by field teams
their immune

Abbreviations: DS, dietary supplements; COVID-19, Coronavirus disease 2019; WHO, World Health Organization; US, United States; UAE, United Arab Emirates;
SPSS, Statistical Package for the Social Sciences.
* Corresponding author.
E-mail address: miraybezirciege@gmail.com (M. Ege).

https://doi.org/10.1016/j.eujim.2023.102249
Received 8 August 2022; Received in revised form 3 April 2023; Accepted 5 April 2023
Available online 6 April 2023
1876-3820/© 2023 Elsevier GmbH. All rights reserved.
M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249

system [7]. In particular, it has been suggested that herbal

Department of Otolaryngology of Adiyaman University between
supplements, as well as vitamins and minerals, could relieve cold and March and September 2021 with various complaints. Literate patients
flu-like symp- toms such as fever, cough, fatigue, sneezing, sore aged ≥ 18 years were enrolled in the study. Patients aged < 18 years,
throat, and muscle pain [8–10]. and those who were illiterate or unable to understand Turkish, were
Many studies have shown that DSs enhance the immune system excluded. The patients were required to fill out the questionnaire
and can have positive effects on disease symptoms [11,12]. In a study carefully. Incomplete
of elderly COVID-19 patients, the use of magnesium, vitamin D, and questionnaires were excluded from the analysis.
vitamin B12 was associated with a significant reduction in the need for
oxygen support and intensive care [13]. In another study, omega-3 2.3. Sample size
supplementation was associated with a lower risk for COVID-19 infec-
tion [14]. The potential therapeutic effects of vitamin C, zinc, vitamin D,
n The following
)/ equation was used) to determine the sample size.
N P Q Z2 d2 N P Q Z2
and probiotics for COVID-19 are currently being studied [15]. = . . .( — 1) + . .
.
Although there is no concrete evidence of the efficacy of DSs for We planned to recruit approximately 500 patients presenting to the
preventing or improving the symptoms of COVID-19, their sales none-
theless increased worldwide during the pandemic. For example,
weekly sales of zinc and elderberry supplements in the United States
(US) increased by 225% and 415%, respectively, during March 2020
[16]. Similarly, in the United Arab Emirates (UAE), there has been a
~200% increase in sales of immune-enhancing supplements [17].
Finally, a study that performed a Google Trends analysis showed that
interest in zinc, vitamins C and D, and herbal supplements such as
garlic, ginger, turmeric, and black elderberry increased worldwide
during the pandemic [18].
Despite potential benefits for the immune system, vitamin, mineral,
and herbal supplements can also have significant disadvantages, such
as side effects and drug interactions, if used without prescription.
More- over, inappropriate use of these products can lead to life-
threatening complications [19]. Obtaining more information
regarding the use rate of these products, and whether patients tend to
seek medical advice before using them, is important to better
understand their efficacy and raise awareness of potential dangers
among patients. DSs are considered safe by most patients and are
commonly used without first seeking advice from a doctor. Moreover,
patients sometimes prefer these prod- ucts to conventional drugs, such
as antivirals. Although DSs are considered to enhance the immune
system, and thus may help to prevent or treat COVID-19, the quality
and quantity of the currently available evidence is insufficient to fully
recommend the use of these supplements [15]. Uncontrolled use of
DSs can result in drug interactions. Moreover, these supplements may
instill false confidence in users such that they might discount other
effective preventive measures and treatments; this poses a serious
threat to public health [20].
In the present study, we investigated the DS use of otorhinolaryn-
gology outpatient patients during the COVID-19 pandemic. The DSs
of interest included herbal and bee products, essential oils, probiotics,
home preparations, omega-3, beta-glucan, and vitamins and minerals.
Our goal was to contribute to the literature by identifying the DSs
typically used by patients after receiving a diagnosis of COVID-19,
and to evaluate the perceived beneficial and/or harmful effects thereof.
We also sought to determine whether the patients received antiviral
drug therapy.

2. Methods

2.1. Ethics and study design

This descriptive and cross-sectional study was ethically reviewed and

approved by the Non-Interventional Research Ethics Committee of
Adiyaman University (Approval number: 2021/02–42). All procedures
were performed in accordance with the ethical principles of the
Helsinki Declaration of 1975, as revised in 2008. After being informed
about the purpose and procedures of the study, patients who wished to
take part provided written informed consent.

2.2. Population

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M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249
[21]
Assuming a population size of 640,000, a total of 2680 COVID-19
infections within a 6-month period, probability of infection of 0.0042,
alpha value of 1%, and effect size of 0.01, the necessary sample size
for this study was determined to be 277.

2.4. Data collection

The questionnaire developed for this study was based on an

extensive literature review of studies on the COVID-19 pandemic and
use of DSs [1,3,10]. The questionnaire items were assessed by two
researchers in terms of relevance, clarity, and adequacy for addressing
the research questions. Changes were made to the questionnaire
according to feed- back provided by the participants in a pilot study
conducted before the main investigation.
The questionnaire has three major sections. The first section
includes nine questions on sociodemographic characteristics (e.g., sex,
age, ed- ucation, smoking status, alcohol intake, and the presence of
systemic diseases), the second section is concerned with DS use
during the pandemic, and the third section includes 12 questions
related to COVID- 19 infection history, including the nutritional
supplements used while infected (if applicable) and disease severity.
The questionnaire was administered in a face-to-face setting by a
single researcher.

2.5. Statistical analysis

The data were analysed using Statistical Package for the Social Sci-
ences (SPSS) software (ver. 25.0; IBM Corp., Armonk, NY, USA).
Continuous variables are reported as means ± standard deviations,
while categorical variables are reported as frequencies and percentages.
The Kolmogorov–Smirnov and Shapiro Wilk tests were used to deter-
mine the normality of the data. P-values < 0.05 were taken to indicate
statistical significance. Pearson’s chi-square test and Fisher’s exact
test were used to analyze categorical variables.

3. Results

After excluding patients who provided incomplete questionnaires

or could not return to the hospital, a total of 277 patients (170 males
[61.37%] and 107 [38.63%] females) were included in this study, with
a mean age of 31.75 ± 12.13 years (range: 18–70 years). The de-
mographic characteristics of the patients are provided in Table 1. In
total, 91.34% of the patients were free from chronic diseases, while
91.70% did not take any regular medications and 66.06% did not
drink or smoke. Moreover, 78.70% of the patients were not health
pro- fessionals, and 45.49% were high school, 35.38% were university
graduates (Table 1).
In total, 139 patients reported taking DSs after the pandemic began
(Fig. 1). The most frequently used vitamins were vitamin C (43.16%),
vitamin D (33.09%), and vitamin B (25.89%), and the most frequently
used minerals were iron (36.7%), zinc (18.7%), and magnesium
(12.23%). Honey (70.5%), propolis (10.07%), and royal jelly (8.63%)
were the most frequently used bee products, and thyme (12.94%),
mint

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M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249

Table 1
Table 2
Demographic, systemic and sociocultural datas.
Usage of dietary supplements after the pandemic.
n % Did you use supportive dietary supplements after the beginning of n (%)
Gender Male 170 61.37% pandemic?
Female 107 38.63%
Yes 139
Total 277 100%
(50.18%)
Age Range / Mean Age 18–70 / 31.75±12.13 No 138
(years) (49.82%)
Marital Status Married 120 43.32% If yes, which of the following did you use? (n=139)
Single 157 56.68% Vitamin supplements n (%)
Residence Province 204 73.65% Vitamin C 60 (43.16%)
County 42 15.16% Vitamin D 46 (33.09%)
Rural 31 11.19% Vitamin B 36 (25.89%)
Presence of chronic disease Yes 24 8.66% Vitamin A 17 (12.23%)
No 253 91.34% Multivitamin 15 (10.79%)
Yes 23 8.30% Vitamin E 8 (5.75%)
Do you regularly use any No 254 91.70% Vitamin K 4 (2.88%)
drug? All 4 (2.88%)
Yes 94 33.94% Mineral supplements n (%)
Do you smoke or drink (cigarettes:65, alcohol:18, Iron 51 (36.70%)
alcohol? both:11) Zinc 26 (18.70%)
No 183 66.06% Magnesium 17 (12.23%)
Educational background Illiterate 6 2.17% Multimineral 6 (4.31%)
Primary-Secondary School 36 13.00% Selenium 5 (3.60%)
High school 126 45.49% Iodine 4 (2.87%)
University 98 35.38% All 1 (0.71%)
Postgraduate 11 3.97% Bee products (n=137*) n (%)
Are you a health Yes 59 21.30% Honey 98 (70.50%)
professional? No 218 78.70% Propolis 14 (10.07%)
Royal jelly 12 (8.63%)
Pollen 11 (7.91%)
All 2 (1.43%)
Treatment with aromatherapy-essential oils (n=86*) n (%)
Thyme 18 (12.94%)
Mint 17 (12.23%)
Tea tree 14 (10.07%)
Clove 12 (8.63%)
Lavender 12 (8.63%)
Eucalyptus 10 (7.19%)
Niaouli 2 (1.43%)
All 1 (0.71%)
Laurel 0 (0%)
Other supplements (n=101*) n (%)
Omega 3 (fish oil) 42 (30.21%)
Probiotics 21 (15.10%)
Vinegar-Carbonate 38 (27.33%)
Herbal supplement usage (n=536*) n (%)
Lemon 76 (54.68%)
Garlic 65 (46.76%)
Ginger 64 (46.04%)
Thyme 61 (43.88%)
Linden 52 (37.41%)
Sage 39 (28.06%)
Sumac 37 (26.61%)
Turmeric 34 (24.46%)
Fig. 1. The use of dietary supplements after the pandemic. Rosehip 29 (20.86%)
Black Seed 28 (20.14%)
Olive Leaf 21 (15.11%)
(12.23%), and tea tree (10.07%) were the most frequently used
Black Mulberry 15 (10.79%)
essential oils (Table 2). Regarding herbal supplements, after the Licorice 6 (4.31%)
COVID-19
pandemic started, lemon (54.68%), garlic (46.76%), ginger (46.04%), Black Elderberry 5 (3.60%)
thyme (43.88%), linden (37.41%), and sage (28.06%) were all widely Echinacea 2 (1.43%)
used, whereas echinacea (1.43%), pelargonium (0.71%), and ginseng Pelargonium 1 (0.71%)
Gingseng 1 (0.71%)
(0.71%) were used relatively infrequently (Fig. 2). Herbal supplements How did you use these products? (n=162*) n (%)

doctors (32.37%), friends and relatives (29.49%), or pharmacists While 45% of these patients were treated exclusively with
(22.3%). antivirals
In total, 131 (47.29%) of the participants had been diagnosed with
COVID-19, the most common symptoms of which were joint, muscle,
and back pain (54.96%), weakness (50.38%), loss of smell (45.80%),
cough (45.80%), and loss of taste (42.75%) (Table 3). Of the COVID-
19 patients, 61.07% were treated at home, while 17.56% were treated
as outpatients, 16.80% as inpatients, and 4.58% in intensive care units.
4
were often consumed in teas (52.52%) and foods (30.22%), which were Herbal tea 73 (52.52%)
usually purchased from herbalists (48.92%) and pharmacies (43.88%). As food 42 (30.22%)
Finally,
M. Koparal the
and patients
M. Ege often used DSs in accordance with the advice of In drug form European Journal of Integrative Medicine 60 32 (23.02%)
(2023) 102249
Inhalation-spray 9 (6.47%)
Mouthwash 6 (4.32%)
Where did you obtain these products? (n=163*) n (%)
Herbalist 68 (48.92%)
Pharmacy 61 (43.88%)
Relatives/friends 27 (19.42%)
Internet 7 (5.03%)
Who suggested these products or where did you hear about them? n (%)
(n=171*)
(continued on next page)

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M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249

Table 2 (continued )
4. Discussion
Did you use supportive dietary supplements after the beginning of
pandemic? n (%)
The present study used a comprehensive questionnaire to evaluate
Doctor 45 (32.37%) DS use among patients presenting to an otolaryngology clinic during
Relatives/friends 41 (29.49%) the COVID-19 pandemic, including patients who experienced COVID-
Pharmacist 31 (22.30%) 19 infection. Information about the perceived benefits and harms of the
Other healthcare professionals 19 (13.67%) DSs was obtained. Despite the great interest in DSs among the general
Herbalist 18 (12.95%)
population during the COVID-19 pandemic, there have been few
Social media/internet 17 (12.23%)
studies on this topic [16–18]. In one previous study, approximately
* Multiple answers were given. 46% of participants reported regularly using natural or herbal DSs to
enhance their immune system during the pandemic [22]. A cross-
(favipiravir) provided by the Ministry of Health, 31.30% of them never sectional study found that 62.8% of participants, recruited from three
used these drugs (Table 3). different coun- tries, used DSs including herbal preparations, vitamins,
In total, 88 (67.18%) of the 131 patients in this study who had and minerals during the first 3 months of the COVID-19 pandemic
experienced COVID-19 infection used DSs for therapeutic purposes [23]. In another study, approximately 32% of patients who presented to
during their illness (Fig. 3). The most frequently used vitamins were a chest diseases clinic during the pandemic used herbal DSs [24].
vitamin C (57.95%), vitamin D (35.23%), and vitamin B (27.27%), Approximately half of our patients (50.18%) used DSs; the high rates
and the most popular minerals were iron (34.09%), multiminerals of DS use during the pandemic could be explained by the limited
(25%), and zinc (18.18%). Honey (70.45%), propolis (7.95%), and treatment options available for COVID-19, people’s desire to
pollen (5.68%) were the most popular bee products, and thyme strengthen their immune systems, and the high availability of DSs.
(18.18%), mint (10.23%) and cloves (9.09%) were the most frequently Almost half of the participants (47.29%) in our study had previously
used essential oils (Table 3). The most widely used herbal supplements tested positive for COVID-19, and 67.18% of those patients used DSs
were lemon (64.77%), ginger (57.95%), thyme (47.73%), and to treat their disease. Among 17.9% of participants in a previous study
linden (47.73%) who had COVID-19, only 35.5% used DSs [25]. In another study,
(Fig. 4). 14.9% of participants used herbal or nutritional supplements to protect
In total, 75 of the 88 patients who had experienced COVID-19 them- selves against COVID-19 infection during the pandemic, and
infection stated that they benefited from using DSs, and no patients re- only 0.6% contracted the disease [7]. Finally, another study reported
ported being harmed by these supplements. In addition, 85.23% of the that 9.2% of participants were diagnosed with COVID-19, 80% of
patients primarily used supplements to enhance their immune system, whom used herbal DSs [26]. The high rate of COVID-19 infection in
although 32.95% used them to prevent coughs and 26.14% to improve our study compared to the literature may be due to the inclusion of
breathing. While 37.50% of the patients stated that the use of DSs patients presenting to a clinic for treatment. In addition, the results of
completely cured their COVID-19 symptoms, 53.41% reported that they previous studies may have been affected by the season and country in
only partially addressed the symptoms, and 9.09% felt that they had no which they were conducted. In particular, there are regional
positive effects. Finally, 63.64% of the patients used DSs without differences in dietary and drug use habits, as well as the level of
informing their doctors (Table 3). awareness of COVID-19.
Among the 131 patients who had experienced COVID-19 infection, In a study by Selcuk et al., the most widely used DSs during the
we found no statistically significant differences in the prevalence rates of pandemic were vitamin D (51.6%), multivitamins (31.0%), and
the various symptoms between those who used DSs and those who did vitamin C (27.0%) [25], while in Radwan et al’s study. the most
not (p > 0.05). However, patients who used DSs were significantly preferred sup- plements were vitamin C (84.5%) and vitamin D
less likely to be hospitalised (p < 0.05). Finally, a statistically (31.6%) [27]. Altun et al. found that the most frequently used
significant preference for DSs over conventional treatment was
observed, regard- supplements were fish oil, vitamin D, and multivitamins [28]. In our
less of whether conventional treatment was actually provided (p < study, vitamin C (43.16%) and vitamin D (33.09%) were the most
0.05) (Table 4). popular supplements, in line with the literature; this also applied to the
subgroup of patients who had experienced COVID-19 infection
(vitamin C, 57.95%; vitamin D, 35.23%).
The antimicrobial effects of vitamin D have been well-documented

Fig. 2. The most commonly used dietary supplements during the pandemic process.
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M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249

Table 3
Table 3 (continued )
Dietary supplement usage situations of patients who have had COVID-19.
Did you have COVID? n (%)
Did you have COVID? n (%)
Garlic 29 (32.95%)
Yes 131 Sage 23 (26.13%)
(47.29%) Turmeric 21 (23.86%)
No 146 Black Seed 20 (22.73%)
(52.71%) Sumac 18 (20.45%)
If yes, did you experience the disease symptoms? n=131 Rosehip 8 (0.09%)
Yes 123 Olive Leaf 6 (6.82%)
(93.90%) Black Mulberry 6 (6.82%)
No 8 (6.11%) Gingseng 5 (5.68%)
Which of the following is/are the symptoms if you had COVID? n¼406* Licorice 3 (3.41%)
(n=131) Black Elderberry 2 (2.27%)
Joint, muscle, back pain 72 (54.96%) Echinacea 2 (2.27%)
Weakness 66 (50.38%) Pelargonium 1 (1.13%)
Loss of smell 60 (45.80%) Did you see any benefit from these supplements? n=88
Cough 60 (45.80%) Yes 75 (85.23%)
Loss of taste 56 (42.75%) No 13 (14.77%)
High fever 45 (34.35%) Did you suffer any harm from these supplements? n=88
Shortness of breath 26 (19.85%) Yes 0 (0%)
Diarrhea- vomiting 21 (16.03%) No 88 (100%)
How did you get over the disease if you had COVID? n=131 For what purpose did you use these supplements? n=154*
At home 80 (61.07%) To enhance immunity 75 (85.23%)
Outpatient clinic treatment 23 (17.56%) To prevent cough 29 (32.95%)
Hospitalization 22 (16.80%) To breath comfortably 23 (26.14%)
Intensive care unit 6 (4.58%) To have back the sense of smell 15 (17.04%)
Did you use conventional treatment and antiviral drugs during n=131 To have back the sense of taste 12 (13.64%)
COVID? What kind of improvement was there in your COVID-related n=88
Completely used 59 (45.04%) symptoms after these supplements?
Used for a short time 31 (23.66%) Partially improved 47 (53.41%)
Never used 41 (31.30%) Completely improved 33 (37.50%)
Did you use dietary supplements except conventional treatment for n=131 No improvement 8 (9.09%)
treatment purpose during your COVID disease? Did you inform your doctor when using supportive food n=88
Yes 88 (67.18%) supplements?
No 43 (32.82%) Yes 32 (36.36%)
If yes, which of the following did you use? (n=88) No 56 (63.64%)

Vitamin supplements n=141*

* Multiple answers were given.
Vitamin C 51 (57.95%)
Vitamin D 31 (35.23%)
Vitamin B 24 (27.27%) [29,30]. Vitamin D may reduce the risk for acute respiratory tract in-
Multivitamin 18 (20.45%)
fections by suppressing the proliferation of infected cells and
Vitamin A 12 (13.63%)
Vitamin K 4 (4.54%)
production of inflammatory cytokines, increasing angiotensin-
All 1 (1.14%) converting enzyme 2 concentrations, and promoting endothelial
Mineral supplements (n=88) n=85* integrity [29–34]. In the meta-analysis of Pereira et al., an association
Iron 30 (34.09%) between vitamin D defi- ciency and COVID-19 severity was found
Multimineral 22 (25.00%)
[35]. Fourteen observational studies have reported inverse correlations
Zinc 16 (18.18%)
Magnesium 8 (9.09%)
between serum concentra- tions of 25-hydroxyvitamin D and both the
Selenium 7 (7.95%) incidence and severity of COVID-19 [33]. Although there is a need for
Iodine 2 (2.27%) experimental and clinical validation, the data suggest that vitamin D
All 0 (0%) supplementation can be beneficial for COVID-19 patients. In
Bee products n=78*
particular, vitamin C has strong antioxidant and antiviral effects
Honey 62 (70.45%)
Royal jelly 7 (7.95%) [35,36]. Vitamin C merits detailed investigation as a therapeutic agent
Pollen 5 (5.68%) with potential for preventing COVID-19 infection and intensive care
Propolis 4 (4.54%) unit admittance, given its anti- oxidant, antiinflammatory, and
All 0 (0%) immunomodulatory effects [37,38]. Current evidence of the efficacy of
Treatment with aromatherapy-essential oils n=48*
Thyme 16 (18.18%)
vitamin C for the treatment of res- piratory diseases is insufficient;
Mint 9 (10.23%) while some studies have reported little or no effect, one showed that a
Clove 8 (9.09%) daily 1–2 g dose of vitamin C was a safe and cost-effective way to
Lavender 5 (5.68%) reduce the duration and severity of colds in people exposed to high
Eucalyptus 5 (5.68%)
levels of stress [39,40]. However, whether high-dose vitamin C
Tea tree 4 (4.54%)
Laurel 1 (1.13%)
supplementation is safe and effective for COVID-19 patients remains to
Niaouli 0 (0%) be proven [37,41]. Rawat et al. conducted a meta-analysis of
All 0 (0%) randomised controlled studies that have investigated the role of
Other supplements n=71* vitamin C supplementation for such patients but reported no
Omega 3 (fish oil) 18 (20.45%)
therapeutic benefits and emphasised that more studies are needed [38].
Probiotics 16 (18.18%)
Vinegar-Carbonate 37 (42.04%) Although data on the use of vitamins for the prevention and treatment
Herbal supplement usage n=336* of COVID-19 are limited, our results are in accordance with the
Lemon 57 (64.77%) literature in showing that vitamin C and D supplements are
Ginger 51 (57.95%) increasingly being used to prevent and treat the disease.
Thyme 42 (47.73%)
Vitamins and trace elements, such as zinc, iron, selenium, magne-
Linden 42 (47.73%)
sium, and copper, as well as omega-3 fatty acids including eicosa-
pentaenoic acid and docosahexaenoic acid, have a physiologically
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M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249

Fig. 3. COVID-19 positive/negative status of patients and the use of dietary supplements (DS).

Fig. 4. The most commonly used dietary supplements in the disease process of patients with COVID-19.

important role in supporting the immune system. In particular, zinc

Vietnamese population, of 74.7% [45], which is similar to that in our
and iron are necessary for enzymatic and physiological processes.
cohort (71.53%). The rate was slightly lower among the patients in our
Because it reduces antiviral immunity, zinc deficiency predisposes
study who had experienced COVID-19 infection (70.45%). The use rates
patients to viral infections such as herpes simplex, the common cold,
of other bee products, such as propolis, pollen, and royal jelly, were
hepatitis C, severe acute respiratory syndrome coronavirus 1, and
considerably lower than that of honey.
human immunodefi- ciency virus [42]. The use of zinc and iron
The use of herbal products believed to enhance immunity increased
supplements among the general population increased during the
during the COVID-19 pandemic [24]. Many medicinal plants, such as
COVID-19 pandemic [25,27, 28]. In our cohort, the most widely used
black elderberry, garlic, ginger, turmeric, lemon balm, and thyme, are
mineral supplements were iron and zinc, which is in line with the
used as antivirals. The antiviral effects of some of these herbs have
literature. Moreover, we found that these supplements were
been demonstrated in the context of various viruses, and are attributed
particularly popular among patients who con- tracted COVID-19.
to their phytochemical components. However, no comprehensive study
Bee products have therapeutic potential due to their ability to
of the activities of plants used as antivirals has been conducted [46]. In
enhance immunity. Since ancient times, bee products have been widely
particular, empirical data supporting the therapeutic use of herbal
used to combat diseases such as colds and flu. In particular, honey and
products for COVID-19 are limited [47]. Nevertheless, as stated above,
propolis are rich in bioactive compounds that exhibit potent antimi-
the use of such products in various forms increased during the
crobial, bactericidal, antiviral, antiinflammatory, immunomodulatory,
pandemic [48]. Erarslan et al. reported that 45 plant species were used
and antioxidant activities [43]. Duarte et al. found that, among
for ther- apeutic purposes during the pandemic, among which ginger
COVID-19 patients receiving inpatient treatment, those using a combi-
(Zingiber officinale), linden (Tilia), elderberry (Sambucus nigra L.),
nation of green Brazilian propolis, honey, and black seed achieved
sage (Salvia), and rosehip (Rosa canina L.) were the most popular
earlier viral clearance, symptom improvement, and hospital discharge
[24]. Furthermore, 63 and 23 plant species were used for the same
than patients receiving standard care, and also had a lower mortality
purpose in Nepal and Morocco, particularly ginger (Zingiber officinale
rate [44]. Radwan et al. reported a honey consumption rate of 42.2% in
Roscoe) [49,50]. In one study, ginger (79.1%) and garlic (64.7%) were
their analysis of dietary habits and DS use during the COVID-19
the most widely used herbal products [45]; in another, ginger (87.1%),
pandemic [27]. Nguyen et al. noted an even higher use rate in a
onion (83.1%), and garlic (78.9%) were all widely consumed during the
pandemic and green

8
M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249

Table 4
experienced COVID-19 infection felt that they had benefitted from the
Relationship of dietary supplement usage after the pandemic and COVID-19.
use of DSs. More specifically, 37.50% of these patients believed that
the
Patients who had supplements healed their symptoms, while 53.41% stated that they had
Options Those who Those who did p
COVID (n=131)
used dietary not use a partial healing effect and 9.09% reported no symptom relief. None of
supplements dietary our patients reported that their DSs caused them any harm. However, it
during COVID supplements
should be noted that these results were obtained through subjective
n=88 during COVID
n=43 self- report measures, and the potential harms of DSs in the context of
COVID-
19 have received little attention. Therefore, more comprehensive studies
Joint muscle- 42 31 0.198
Which of the back pain on this issue are needed.
following is/ Another important issue associated with DSs concerns the informa-
Weakness 44 29 0.079
are the
Loss of smell 50 35 0.104 tion sources consulted prior to their use. The most popular sources of
symptoms if
Cough 46 37 0.323 information about DSs before the COVID-19 pandemic began were
you had
Loss of taste 39 26 0.107
COVID? * television programs, the internet and social media networks, herbalists,
High fever 22 29 0.327 and friends [51]. Radwan et al. reported that, during the pandemic, their
Shortness of 47 34 0.149
breath participants (all of whom were residing in the UAE) frequently
Diarrhea- 16 12 0.450 obtained information from social media (40%) and relatives/friends
vomiting (29%) [27]. Similarly, Alyami et al. reported that the most popular
source of infor-
At home 54 16 0.000
mation during the pandemic was social media and internet networks
How did you (39.4%), followed by friends and relatives [7]. The participants in Sel-
Outpatient 16 11 0.336
get over the
clinic cuk et al. typically received information on DSs via health
disease if you
treatment professionals and the internet [25]. The main sources of information
about the DSs in
had COVID? Hospitalization 12 9 0.513 our study were doctors (32.37%), friends and relatives (29.49%), and

Did you use Intensive care 6 7 0.782

unit pharmacists (22.3%); this can be explained by our inclusion of patients
conventional
treatment who visited a clinic during the pandemic.
Completely 45 24 0.011 Although DSs can be widely obtained without a prescription, for
used reasons of safety and quality they should be purchased from licensed
Used for a short 24 13 0.071
time pharmacies under the guidance of a clinician. Our patients mainly
during COVID?
Never used 19 6 0.009 purchased DSs from herbalists (48.92%) and pharmacies (43.88%).
Herbalists may have been frequently used because they stock both
dietitians during the pandemic, most of whom cited protection against
* Multiple answers were given.
COVID-19 infection as the main reason for taking supplements [28].
P ˂0.05. Pearson’s and Fisher’s exact chi-square tests were used.
The patients in our study who had experienced COVID-19 used DSs
primarily to enhance immunity (85.23%), although prevention of cough
(84.7%), ginger (56.4%), and thyme (27.4%) teas were the most
(32.95%) and breathing improvement (26.14%) were also cited.
popular herbal teas [27].
Overall, our re- sults support those reported in the literature.
In Bulut et al., the most frequently used herbal supplements were The majority (85.23%) of the patients in our study who had
turmeric (20.4%), ginger (12.2%), green tea (4.1%), and echinacea
(4.1%) [24], compared to lemon (54.68%), garlic (46.76%), ginger
(46.04%), thyme (43.88%), and linden (37.41%) in our study.
Similarly, many of the patients in our study who had experienced
COVID-19 infection used lemon (64.77%), ginger (57.95%), thyme
(47.73%), linden (47.73%), and garlic (32.95%) supplements. We
suggest that variation in the use rates of supplements among regions
may reflect cultural differences.
Our literature search revealed very few studies on the use of
essential oils for treating COVID-19. However, the use of essential oil
sprays to treat loss of smell, which is common in COVID-19, has been
reported. In our cohort, the most widely used essential oils during the
pandemic were thyme, mint, and tea tree, while thyme, mint, and clove
essential oils were the most popular essential oils among the patients
who had experienced COVID-19 infection.
A Google Trends analysis revealed that the main reason for using DSs
during the COVID-19 pandemic was to enhance immunity [18]. In line
with this, participants in Selcuk et al. cited immune system enhance-
ment (77.0%), general health benefits (56.3%), and protection against
COVID-19 infection (32.5%) as the main reasons for taking DSs
during the pandemic [25]. Nguyen et al. reported that herbal products
were used by their questionnaire respondents to treat sore throat,
cough, and nasal obstruction [45]. Altun et al. studied DS use among
9
M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249
herbal teas and food products. The small proportion (5.03%) of
patients in our study who purchased DSs via the internet may be
attributable to increased consumer awareness of the importance of
product safety since the COVID-19 pandemic began.
Many patients do not disclose the use of DSs to their doctor or
pharmacist because they consider such products to be safe [51]. In our
study, 63.64% of the patients did not disclose their DS use to a doctor.
The implementation of mandatory quarantines and curfews during the
pandemic, as well as the reluctance of many people to enter a hospital
environment because of the high risk of COVID-19 transmission, may
have reduced patient interactions with doctors. In addition, and as
stated above, DSs and natural products are widely considered safe,
such that patients may not feel it necessary to disclose their use to
doctors. This perception can be explained by the high availability of
DSs, which can be purchased from markets in many countries, as well
as from herbalists and online retailers without a prescription.
Unlike previous studies, we examined the effect of DS use on COVID-
19 symptoms and found that patients who took these supplements
while infected were more likely to recover at home (i.e., to avoid
being hos- pitalised) than those who did not take DSs; however, the
difference was not statistically significant. Moreover, as a novel
finding, our patients preferred DSs to conventional treatment,
regardless of whether such treatment was actually provided.
Many patients presented to outpatient clinics with COVID-19
symptoms during the pandemic. However, to the best of our knowl-
edge, our study is the first to assess DS use among patients who pre-
sented to an otorhinolaryngology clinic, and to compare use rates
between patients with and without COVID-19 infection. In the
majority of questionnaire studies on this topic, the participants were
not specif- ically asked about the DSs that they used when actually
infected with COVID-19. Furthermore, we classified the DSs in a
comprehensive manner and examined both their benefits and harms.
Therefore, although our study included a relatively low number of
patients, it nonetheless provides important information; the findings
could inform campaigns to promote safe and effective use of DSs
among people with COVID-19.
One of the main limitations of this study was its relatively small

10
M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249

population; many patients did not provide sufficient questionnaire re- beliefs about and use of herbal products during the COVID-19 pandemic: a
sponses because they did not want to remain in the hospital environ- cross- sectional study in Saudi Arabia, Saudi Pharm. J. 28 (2020) 1326–1332,
ment. However, unlike many other surveys conducted during the https://doi. org/10.1016/j.jsps.2020.08.023.
[8] K. Khanna, S.K. Kohli, R. Kaur, A. Bhardwaj, V. Bhardwaj, P. Ohri, A. Sharma,
COVID-19 pandemic, we conducted one-on-one interviews rather than
A. Ahmad, R. Bhardwaj, P. Ahmad, Herbal immune-boosters: substantial warriors
using an online survey format, which enhanced the reliability of the of pandemic COVID-19 battle, Phytomedicine 85 (2021), 153361,
data. Nevertheless, it would have been preferable to recruit a larger https://doi.org/ 10.1016/j.phymed.2020.153361.
[9] Y. Yang, M.S. Islam, J. Wang, Y. Li, X. Chen, Traditional Chinese Medicine in the
number of patients from more than one region.
treatment of patients infected with 2019-new coronavirus (SARS-CoV-2): a review
and perspective, Int. J. Biol. Sci. 16 (2020) 1708–1717, https://doi.org/10.7150/
5. Conclusion ijbs.45538.
[10] H. Luo, Q.L. Tang, Y.X. Shang, S.B. Liang, M. Yang, N. Robinson, J.P. Liu, Can
Chinese medicine be used for prevention of corona virus disease 2019 (COVID-
This study explored the use of dietary supplements (DSs), 19)? A review of historical classics, research evidence and current prevention
including vitamins, minerals, bee products, and aromatherapy programs, Chin. J. Integr. Med. 26 (2020) 243–250,
products, by pa- tients who attended to a hospital otolaryngology clinic https://doi.org/10.1007/s11655-020-
3192-6.
during the pandemic. Many patients reported using DSs to enhance [11] C.E. Childs, P.C. Calder, E.A. Miles, Diet and immune function, Nutrients 11
their immune system during the pandemic. However, inappropriate use (2019) 1933, https://doi.org/10.3390/nu11081933.
of these products can be dangerous; therefore, patient awareness of [12] F. Moscatelli, F. Sessa, A. Valenzano, R. Polito, V. Monda, G. Cibelli, I. Villano,
D. Pisanelli, M. Perrella, A. Daniele, M. Monda, G. Messina, A. Messina, COVID-19:
possible side effects should be improved. Further studies are needed to role of nutrition and supplementation, Nutrients 13 (2021) 976, https://doi.org/
confirm the benefits of DSs for the management of COVID-19. 10.3390/nu13030976.
[13] C.W. Tan, L.P. Ho, S. Kalimuddin, B. Cherng, Y.E. Teh, S.Y. Thien, H.M. Wong,
P. Tern, M. Chandran, J. Chay, C. Nagarajan, R. Sultana, J. Low, H.J. Ng,
Financial support
Cohort study to evaluate the effect of vitamin D, magnesium, and vitamin B12
in combination on progression to severe outcomes in older patients with
This research did not receive any specific grant from funding coronavirus (COVID-19), Nutrition 79-80 (2020), 111017,
agencies in the public, commercial, or not-for-profit sectors. https://doi.org/10.1016/j. nut.2020.111017.
[14] P. Louca, B. Murray, K. Klaser, et al., Modest effects of dietary supplements during
the COVID-19 pandemic: insights from 445 850 users of the COVID-19 Symptom
CRediT authorship contribution statement Study app, BMJ Nutr. Prev. Health 4 (2021) 149–157, https://doi.org/10.1136/
bmjnph-2021-000250.
[15] NIH Dietary Supplements in the Time of COVID-19-Health Professional Fact
Mehtap Koparal: Conceptualization, Investigation, Writing – review Sheet https://ods.od.nih.gov/factsheets/COVID19-HealthProfessional/#en8
& editing, Supervision. Miray Ege: Conceptualization, Investigation, (accessed 10 June 2021).
Writing – original draft, Writing – review & editing, Supervision. [16] J. Grebow, Dietary supplement sales skyrocket during coronavirus pandemic, https
://www.nutritionaloutlook.com/view/dietary-supplement-sales skyrocket
during coronavirus-pandemic (accessed 16 June 2021).
Declaration of Competing Interest [17] A. Kumar, COVID-19: 200% rise in demand for supplements in UAE pharmacies –
News Khaleej Times, https://www.khaleejtimes.com/coronavirus-pandemic/
COVID-19-200-rise-in-demand forsupplements-in-uae-pharmacies (accessed 16
The authors declare that they have no known competing financial June 2021).
interests or personal relationships that could have appeared to [18] J. Hamulka, M. Jeruszka-Bielak, M. Go´rnicka, M.E. Drywien´, M.A. Zielinska-Pukos,
influence the work reported in this paper. Dietary supplements during COVID-19 outbreak. Results of google trends analysis
supported by PLifeCOVID-19 online studies, Nutrients 13 (2020) 54, https://doi.
org/10.3390/nu13010054.
Data availability [19] M.J.J. Ronis, K.B. Pedersen, J. Watt, Adverse effects of nutraceuticals and dietary
supplements, Annu. Rev. Pharmacol. Toxicol. 58 (2018) 583–601, https://doi.org/
10.1146/annurev-pharmtox-010617-052844.
Research data is available upon request. Data can be obtained from
[20] S. Wiesener, A. Salamonsen, V. Fønnebø, Which risk understandings can be
the corresponding author via email. derived from the current disharmonized regulation of complementary and
alternative medicine in Europe? BMC Complement. Altern. Med. 18 (2018) 11,
Acknowledgments https://doi. org/10.1186/s12906-017-2073-9.
[21] K. Ozdamar, Biostatistics With SPSS, 10th ed., Nisan Bookstore Publications,
Eskisehir, 2015.
None. [22] A. Abdullah Alotiby, L. Naif Al-Harbi, Prevalence of using herbs and natural
products as a protective measure during the COVID-19 pandemic among the Saudi
population: an online cross-sectional survey, Saudi Pharm. J. 29 (2021) 410–417,
References https://doi.org/10.1016/j.jsps.2021.04.001.
[23] A.E. Kristoffersen, E.T. van der Werf, T. Stub, F. Musial, B. Wider, M.C. Jong,
[1] World Health Organization (WHO) Q & A on coronaviruses (COVID-19). https:// K. Wode, J.B. Danell, M. Busch, H. Hoenders, J.H. Nordberg, Consultations with
www.who.int/news-room/q-a-detail/q-acoronaviruses (accessed 6 July 2020). health care providers and use of self-management strategies for prevention and
[2] B. Vellingiri, K. Jayaramayya, M. Iyer, A. Narayanasamy, V. Govindasamy, treatment of COVID-19 related symptoms. A population based cross-sectional
B. Giridharan, S. Ganesan, A. Venugopal, D. Venkatesan, H. Ganesan, study in Norway, Sweden and the Netherlands, Complement. Ther. Med. 64
K. Rajagopalan, P. Rahman, S.G. Cho, N.S. Kumar, M.D. Subramaniam, COVID- (2022), 102792, https://doi.org/10.1016/j.ctim.2021.102792.
19: a promising cure for the global panic, Sci. Total. Environ. 725 (2020), 138277, [24] S. Bulut, B.O. Sahin, N.Y. Demirci, D.D. Orhan, Investigation of the usage of
https://doi.org/10.1016/j.scitotenv.2020.138277. herbal products during the COVID-19 pandemic, J. Res. Pharm. 25 (2021) 913–
[3] C. Sohrabi, Z. Alsafi, N. O’Neill, M. Khan, A. Kerwan, A. Al-Jabir, C. Iosifidis, 919, https://doi.org/10.29228/jrp.88.
R. Agha, World Health Organization declares global emergency: a review of [25] T.K. Selcuk, N. Sahin, Dietary supplement use in adults and related factors
the 2019 novel coronavirus (COVID-19), Int. J. Surg. 76 (2020) 71–76, during the COVID-19 epidemic, TJFMPC 15 (2021) 751–762,
https://doi. org/10.1016/j.ijsu.2020.02.034. https://doi.org/10.21763/ tjfmpc.980495.
[4] Y. Demirbilek, G. Pehlivanturk, Z.O. Ozguler, E. Alp Mes¸e, COVID-19 [26] Z.B. Erarslan, S. Kultur, A cross-sectional survey of herbal remedy taking to
outbreak control, example of ministry of health of Turkey, Turk. J. Med. Sci. 50 prevent COVID-19 in Turkey, J. Res. Pharm. 25 (2021) 920–936, https://doi.org/
(2020) 489–494, https://doi.org/10.3906/sag-2004-187. 10.29228/jrp.89.
[5] S.P. Adhikari, S. Meng, Y.J. Wu, Y.P. Mao, R.X. Ye, Q.Z. Wang, C. Sun, S. Sylvia, [27] H. Radwan, H. Hasan, Z. Jaafar, N. Abbas, E. Rashed Saif, M. Al Kitbi, M. Al Hilali,
S. Rozelle, H. Raat, H. Zhou, Epidemiology, causes, clinical manifestation and F. Naja, Diets and dietary supplements used during the COVID-19 pandemic in the
diagnosis, prevention and control of coronavirus disease (COVID-19) during the United Arab Emirates: a cross-sectional survey, Saudi Pharm. J. 30 (2022)
early outbreak period: a scoping review, Infect. Dis. Poverty 9 (2020) 29, 421–432, https://doi.org/10.1016/j.jsps.2022.01.019.
https:// doi.org/10.1186/s40249-020-00646-x. [28] H. Kamarli Altun, M.S. Karacil Ermumcu, N. Seremet Kurklu, Evaluation of
[6] C. Liu, Q. Zhou, Y. Li, L.V. Garner, S.P. Watkins, L.J. Carter, J. Smoot, A.C. Gregg, dietary supplement, functional food and herbal medicine use by dietitians
A.D. Daniels, S. Jervey, D. Albaiu, Research and development on therapeutic during the COVID-19 pandemic, Public Health Nutr. 24 (2021) 861–869,
agents and vaccines for COVID-19 and related human coronavirus diseases, ACS https://doi.org/ 10.1017/S1368980020005297.
Cent. Sci. 6 (2020) 315–331, https://doi.org/10.1021/acscentsci.0c00272. [29] A.R. Martineau, N.G. Forouhi, Vitamin D for COVID-19: a case to answer? Lancet
[7] H.S. Alyami, M.A.A. Orabi, F.M. Aldhabbah, H.N. Alturki, W.I. Aburas, A.I. Alfayez, Diabetes Endocrinol. 8 (2020) 735–736, https://doi.org/10.1016/S2213-8587(20)
A.S. Alharbi, R.A. Almasuood, N.A. Alsuhaibani, Knowledge about COVID-19 and 30268-0.

11
M. Koparal and M. Ege European Journal of Integrative Medicine 60 (2023) 102249

[30] B. Prietl, G. Treiber, T.R. Pieber, K. Amrein, Vitamin D and immune function,
Nutrients 5 (2013) 2502–2521, https://doi.org/10.3390/nu5072502. [42] N. Samad, T.E. Sodunke, A.R. Abubakar, I. Jahan, P. Sharma, S. Islam, S. Dutta,
[31] A.V. Yamshchikov, N.S. Desai, H.M. Blumberg, T.R. Ziegler, V. Tangpricha, M. Haque, The implications of zinc therapy in combating the COVID-19 global
Vitamin D for treatment and prevention of infectious diseases: a systematic review pandemic, J. Inflamm. Res. 14 (2021) 527–550, https://doi.org/10.2147/JIR.
of randomized controlled trials, Endocr. Pract. 15 (2009) 438–449, https://doi. S295377.
org/10.4158/EP09101.ORR. [43] A.M. Ali, H. Kunugi, Propolis, bee honey, and their components protect against
[32] D.A. Jolliffe, C.A. Camargo, J.D. Sluyter, et al., Vitamin D Supplementation to coronavirus disease 2019 (COVID-19): a review of in silico, in vitro, and
Prevent Acute Respiratory Infections: Systematic Review and Meta-Analysis of clinical studies, Molecules 26 (2021) 1232,
Aggregate Data from Randomised Controlled Trials, Lancet Diabetes Endocrinol. 9 https://doi.org/10.3390/molecules26051232.
(2021) 276–292, https://doi.org/10.1016/S2213-8587(21)00051-6. [44] M.A. Duarte Silveira, D. De Jong, E.B. dos Santos Galv˜ao, et al., Efficacy of propolis
[33] G. Butler-Laporte, T. Nakanishi, V. Mooser, D.R. Morrison, T. Abdullah, O. Adeleye, as an adjunct treatment for hospitalized COVID-19 patients: a randomized,
N. Mamlouk, N. Kimchi, Z. Afrasiabi, N. Rezk, A. Giliberti, A. Renieri, Y. Chen, controlled clinical trial, Biomed. Pharmacother. 138 (2021), 111526, https://doi.
S. Zhou, V. Forgetta, J.B. Richards, Vitamin D and COVID-19 susceptibility and org/10.1016/j.biopha.2021.111526.
severity in the COVID-19 host genetics initiative: a Mendelian randomization [45] P.H. Nguyen, V.D. Tran, D.T. Pham, T.N.P. Dao, R.S. Dewey, Use of and attitudes
study, PLoS Med. 18 (2021), e1003605, https://doi.org/10.1371/journal. towards herbal medicine during the COVID-19 pandemic: a cross-sectional study in
pmed.1003605. Vietnam, Eur. J. Integr. Med. 44 (2021), 101328, https://doi.org/10.1016/j.
[34] J. Mercola, W.B. Grant, C.L. Wagner, Evidence regarding vitamin D and risk of eujim.2021.101328.
COVID-19 and its severity, Nutrients 12 (11) (2020) 3361, https://doi.org/ [46] M. Akram, I.M. Tahir, S.M.A. Shah, Z. Mahmood, A. Altaf, K. Ahmad, N. Munir,
10.3390/nu12113361. M. Daniyal, S. Nasir, H. Mehboob, Antiviral potential of medicinal plants against
[35] M. Pereira, A. Dantas Damascena, L.M. Galv˜ao Azevedo, T. de Almeida Oliveira, HIV, HSV, influenza, hepatitis, and coxsackievirus: a systematic review, Phytother.
J. da Mota Santana, Vitamin D deficiency aggravates COVID-19: systematic Res. 32 (2018) 811–822, https://doi.org/10.1002/ptr.6024.
review and meta-analysis, Crit. Rev. Food Sci. Nutr. 62 (2022) 1308–1316, [47] M.T. Islam, C. Sarkar, D.M. El-Kersh, S. Jamaddar, S.J. Uddin, J.A. Shilpi, M.
https://doi. org/10.1080/10408398.2020.1841090. S. Mubarak, Natural products and their derivatives against coronavirus: a review of
[36] A.C. Carr, S. Maggini, Vitamin C and immune function, Nutrients 9 (2017) 1211, the non-clinical and pre-clinical data, Phytother. Res. 34 (2020) 2471–2492,
https://doi.org/10.3390/nu9111211. https://doi.org/10.1002/ptr.6700.
[37] A.C. Carr, A new clinical trial to test high-dose vitamin C in patients with COVID- [48] I.A. Kretchy, J.A. Boadu, J.P. Kretchy, K. Agyabeng, A.A. Passah, A. Koduah, K.F.
19, Crit. Care 24 (2020) 133, https://doi.org/10.1186/s13054-020-02851-4. M. Opuni, Utilization of complementary and alternative medicine for the
[38] D. Rawat, A. Roy, S. Maitra, A. Gulati, P. Khanna, D.K. Baidya, Vitamin C and prevention of COVID-19 infection in Ghana: a national cross-sectional online
COVID-19 treatment: a systematic review and meta-analysis of randomized survey, Prev. Med. Rep. 24 (2021), 101633, https://doi.org/10.1016/j.
controlled trials, Diabetes Metab. Syndr. 15 (2021), 102324, https://doi.org/ pmedr.2021.101633.
10.1016/j.dsx.2021.102324. [49] D. Khadka, M.K. Dhamala, F. Li, P.C. Aryal, P.R. Magar, S. Bhatta, M.S. Thakur,
[39] R.M. Douglas, H. Hemila¨, E. Chalker, B. Treacy, Vitamin C for preventing and A. Basnet, D. Cui, S. Shi, The use of medicinal plants to prevent COVID-19 in Nepal,
treating the common cold, Cochrane Database Syst. Rev. 18 (3) (2007), CD000980, J. Ethnobiol. Ethnomed. 17 (2021) 26, https://doi.org/10.1186/s13002-021-
https://doi.org/10.1002/14651858.CD000980.pub3. 00449-w.
[40] H. Hemil¨a, E. Chalker, Vitamin C for preventing and treating the common [50] A. El Alami, A. Fattah, A. Chait, Medicinal plants used for the prevention purposes
during the COVID-19 pandemic in Morocco, JASAB 2 (2020) 4–11, https://doi.
cold, Cochrane Database Syst. Rev. 2013 (1) (2013), CD000980,
org/10.48402/IMIST.PRSM/jasab-v2i1.21056.
https://doi.org/ 10.1002/14651858.CD000980.pub4.
[41] A.F. Feyaerts, W. Luyten, Vitamin C as prophylaxis and adjunctive medical [51] M. Ege, M.Y. Kurt, B. Ege, M. Koparal, S. Yıldız, Evaluation of the use and
treatment for COVID-19? Nutrition 79-80 (2020), 110948 https://doi.org/ awareness of herbal products of the patients applying to the faculty of dentistry,
10.1016/j.nut.2020.110948. J. Health Sci. Adıyaman Univ. 7 (2021) 146–157, https://doi.org/10.30569/
adiyamansaglik.913016.

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