Advertisement

Usage of nutritional supplements to improve immunity during the COVID-19 pandemic: An online survey

  • Tormalli V. Francis
    Affiliations
    Health and Wellness Unit, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
    Search for articles by this author
  • Piumika Sooriyaarachchi
    Affiliations
    Health and Wellness Unit, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka

    Queensland University of Technology, School of Exercise & Nutrition Sciences, Brisbane, Queensland, Australia
    Search for articles by this author
  • Ranil Jayawardena
    Correspondence
    Corresponding author. Professor in Nutrition Department of Physiology, Faculty of Medicine, University of Colombo, Sri Lanka.
    Affiliations
    Health and Wellness Unit, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka

    Department of Physiology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
    Search for articles by this author
Open AccessPublished:April 18, 2022DOI:https://doi.org/10.1016/j.nutos.2022.04.003

      Summary

      Background and aims

      Proper nutrition to optimise immune function is mandatory as at present there is no specific medicine to cure COVID-19. Our study aimed to investigate the use of nutritional supplements and their key immunity enhancing components among Sri Lankans.

      Methods

      This current study was an online survey conducted during the period from 27th May to 2nd June 2021 disseminated via various social media platforms. Details were collected on highlighting the frequency and composition of nutritional supplements consumed.

      Results

      In a total of 3707 responders, a proportion of 25.5% (944) of the participants took supplements regularly, and 32.6% (1210), 14.5% (538), 27.4% (1015) intake were occasionally, rarely and never respectively. Older participants (>40 years of age) had a significantly higher intake of supplements than the younger counterpart of 31–35 years age group (OR: 0.604; 95% CI, 0.451–0.809; p < 0.001). Almost half (46.0%) took vitamin C supplements and females tend to take more (OR: 1.325; 95% CI, 1.120–1.567; p < 0.001) of vitamin C when compared to males. Comparatively to the other groups regarding monthly income, the participants with the highest income category are more likely to take vitamin D (OR:1.899; 95% CI, 1.034–3.490; p = 0.039) and multivitamin (OR: 3.222; 95% CI, 1.737–5.977; p < 0.001). The most commonly used main ingredient in home-made remedy was coriander in Sri Lanka.

      Conclusion

      The use of nutritional supplements and natural products to improve immunity during the pandemic were frequent among Sri Lankan adults. In general, older, female gender and high income was significantly associated with increased intake of the nutrient supplements.

      Keywords

      Introduction

      The coronavirus disease 2019 (COVID-19) pandemic advanced relentlessly worldwide since the first cluster of cases of infection [
      • Kaswa R.
      • Govender I.
      Novel coronavirus pandemic: a clinical overview.
      ]. As of 31st of May 2021, it has spread over 222 countries, and caused a total of 17 million and 3.5 million active cases and deaths respectively []. The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in a substantial increase in hospitalisations for pneumonia with multi-organ disease worldwide [
      • Wiersinga W.J.
      • Rhodes A.
      • Cheng A.C.
      • Peacock S.J.
      • Prescott H.C.
      Pathophysiology, transmission, diagnosis, and treatment of coronavirus disease 2019 (COVID-19): a review.
      ]. Expression of the virus ranges from asymptomatic to life-threatening, presenting flu-like symptoms to severe lung injury in high-risk older individuals with multiple co-morbidities [
      • Pascarella G.
      • Strumia A.
      • Piliego C.
      • Bruno F.
      • del Buono R.
      • Costa F.
      • et al.
      COVID-19 diagnosis and management: a comprehensive review.
      ]. COVID-19 remains a global health challenge, having triggered an enormous number of human causalities and serious economic losses to countries [
      • Ahn D.G.
      • Shin H.J.
      • Kim M.H.
      • Lee S.
      • Kim H.S.
      • Myoung J.
      • et al.
      Current status of epidemiology, diagnosis, therapeutics, and vaccines for novel coronavirus disease 2019 (COVID-19).
      ]. Therefore, infection prevention, early viral detection and identification of treatment protocols provide the best approach in controlling the disease spread.
      Multiple therapeutic strategies are used to treat patients with COVID-19, while no specific drugs are recommended to cure it [
      • Jean S.S.
      • Lee P.I.
      • Hsueh P.R.
      Treatment options for COVID-19: the reality and challenges.
      ]. The fundamental prevention measures such as mask-wearing, social distancing and handwashing are universally recommended [
      • Ma Q.X.
      • Shan H.
      • Zhang H.L.
      • Li G.M.
      • Yang R.M.
      • Chen J.M.
      Potential utilities of mask-wearing and instant hand hygiene for fighting SARS-CoV-2.
      ]. In addition to the basic preventative measures, vaccination has been identified as a key strategy for preventing the infection globally [
      • Chung J.Y.
      • Thone M.N.
      • Kwon Y.J.
      COVID-19 vaccines: the status and perspectives in delivery points of view.
      ]. A substantial population need to be vaccinated to achieve safe herd immunity to control transmission of the COVID-19 virus [
      • Chung Y.H.
      • Beiss V.
      • Fiering S.N.
      • Steinmetz N.F.
      COVID-19 vaccine frontrunners and their nanotechnology design.
      ]. The demand for vaccines is expected to overcome the supply and disparities in vaccine doses across high and low-income countries can be seen [
      ]. In addition, it is well known that proper nutrition can support optimal immune function thus reducing the impact of infections [
      • Pecora F.
      • Persico F.
      • Argentiero A.
      • Neglia C.
      • Esposito S.
      The role of micronutrients in support of the immune response against viral infections.
      ].
      The global burden of the COVID-19 pandemic infection is significant, requiring further safeguards. Achieving a balanced diet has become extremely challenging during this epidemic [
      • Jayawardena R.
      • Misra A.
      Balanced diet is a major casualty in COVID-19. Diabetes and Metabolic Syndrome.
      ]. Protein-energy malnutrition and/or micronutrient deficiency are associated with an impaired immune system [
      • Iddir M.
      • Brito A.
      • Dingeo G.
      • del Campo S.S.F.
      • Samouda H.
      • la Frano M.R.
      • et al.
      Strengthening the immune system and reducing inflammation and oxidative stress through diet and nutrition: considerations during the COVID-19 crisis.
      ,
      • Chandra R.K.
      Protein-energy malnutrition and immunological responses.
      ]. Micronutrient deficiencies are highly prevalent in the South Asian region and deficiencies of iron, zinc, vitamin D and vitamin B12 are well established [
      • Gopalan H.S.
      • Misra A.
      • Jayawardena R.
      Nutrition and diabetes in South Asia.
      ]. A review evaluating nutrition-based interventions for respiratory viral infections, reported vitamins A and D as well as trace minerals like selenium and zinc to have immune-modulatory effects [
      • Jayawardena R.
      • Sooriyaarachchi P.
      • Chourdakis M.
      • Jeewandara C.
      • Ranasinghe P.
      Enhancing immunity in viral infections, with special emphasis on COVID-19: a review.
      ]. Furthermore, the same review showed vitamin C had no beneficial evidence against viral infections, and similarly vitamin E supplementation indicated no effect and may be detrimental [
      • Jayawardena R.
      • Sooriyaarachchi P.
      • Chourdakis M.
      • Jeewandara C.
      • Ranasinghe P.
      Enhancing immunity in viral infections, with special emphasis on COVID-19: a review.
      ]. During this epidemic, commonly recommended supplements by dieticians were fish oil, vitamin D, multivitamin, probiotics, and vitamin C [
      • Kamarli Altun H.
      • Karacil Ermumcu M.S.
      • Seremet Kurklu N.
      Evaluation of dietary supplement, functional food and herbal medicine use by dietitians during the COVID-19 pandemic.
      ].
      Along with micronutrients, natural products with therapeutic properties such as ginger, turmeric, garlic, and others are utilised as home-based remedies which hold immune-modulating properties that may improve immunity against diseases [
      • Sultan M.T.
      • Buttxs M.S.
      • Qayyum M.M.N.
      • Suleria H.A.R.
      Immunity: plants as effective mediators.
      ]. According to a study conducted on the use of herbs and natural products in the Saudi population during the COVID-19 pandemic, 69.3% believed that these practices can improve their immunity [
      • Abdullah Alotiby A.
      • Naif Al-Harbi L.
      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.
      ]. Additionally, a survey in Bangladesh reported that 57.6% of the participants had used herbal foods/products, with tea (71%) being the most popular, followed by ginger (56.5%), black seed (32.8%), honey (30%), and clove (30%) [
      • Ahmed I.
      • Hasan M.
      • Akter R.
      • Sarkar B.K.
      • Rahman M.
      • Sarker M.S.
      • et al.
      Behavioral preventive measures and the use of medicines and herbal products among the public in response to COVID-19 in Bangladesh: a cross-sectional study.
      ].
      Hence, dietary supplements defined as usable amounts of micronutrients have become a growing interest during the COVID-19 as they are widely used to potentially improve immune health [
      • Rautiainen S.
      • Manson J.E.
      • Lichtenstein A.H.
      • Sesso H.D.
      Dietary supplements and disease prevention-a global overview.
      ]. Moreover, complementary and alternate medicine as Ayurveda and herbal supplements are frequently used as treatments globally [
      • Medagama A.B.
      • Bandara R.
      • Abeysekera R.A.
      • Imbulpitiya B.
      • Pushpakumari T.
      Use of complementary and alternative medicines (CAMs) among type 2 diabetes patients in Sri Lanka: a cross sectional survey.
      ]. Sri Lanka as a lower-middle-income country, experienced its most severe outbreak of the COVID-19 pandemic during the study period. Therefore, the main aim of this online survey was to investigate the use of nutritional supplements and their key immunity-enhancing components among Sri Lankans during the COVID-19 pandemic.

      Methods

      Study design and sampling

      The present study is a national-level online survey conducted using Google forms, a web survey platform during the period from 27th May to 2nd June 2021. Recruitment of participants was carried out using multiple strategies. The link to the online survey was circulated across various social media platforms, and the detailed methodology is published elsewhere [
      • Sooriyaarachchi Piumika
      • Francis Tormalli V.
      • King Neil
      • Jayawardena R.
      Increased physical inactivity and weight gain during the COVID-19 pandemic in Sri Lanka: an online cross-sectional survey.
      ]. No incentives were given to the participants and the active promotion of the questionnaire was completely voluntary. Informed consent was taken prior to the administration of the questionnaire. The web-based survey was performed accordingly to the ethical principles laid by the World Medical Association Declaration of Helsinki [
      World Medical Association declaration of Helsinki
      Ethical principles for medical research involving human subjects.
      ]. The nature of anonymity and the impossibility to trace any sensitive data required no ethical approval [
      • Hamulka J.
      • Jeruszka-Bielak M.
      • Górnicka M.
      • Drywień M.E.
      • Zielinska-Pukos M.A.
      Dietary supplements during COVID-19 outbreak. Results of Google trends analysis supported by PLifeCOVID-19 online studies.
      ].

      Questionnaire

      The online questionnaire was constructed using Google Forms and was made available in all three official languages; English, Sinhala, and Tamil. The participants could select the preferred language, and the questionnaire was anticipated to take 5–10 minutes to complete. The questionnaire was divided into two sections, each including personal and lifestyle details, with a focus on the use of nutritional supplements to improve immunity.
      The first section investigated the participants' personal related data. Respondents' details of birth year, gender, district, area of residence, ethnicity, educational status, current employment status, and family details including the monthly income were collected by both open-ended and multiple-choice questions.
      The second part of the questionnaire collected details on the usage of “immune nutrients”. The frequency and composition of nutritional supplements consumed were recorded. The frequency of the supplement intake was inquired using four options: regularly, occasionally, rarely, or never. The respondents were asked to select the nutritional supplements they consumed during this period from a list of nine options: vitamin C, vitamin D, multivitamin, kothamalli (Coriandrum sativum infused in water), Ayurvedic products, herbal products, home-made remedies, syrups, and others. To obtain more details on home-based remedies, the most common ingredient used was asked via an open-ended question.

      Statistical analysis

      Data were extracted from Google forms as an MS Excel spreadsheet (Version 16.50, Microsoft Corporation). The data were revised, coded, and fed into the statistical software IBM SPSS version 23 (SPSS, Inc. Chicago, IL) for statistical analysis. Descriptive analysis based on the frequency and percentage distribution was performed for all demographic variables and the results were expressed as a percentage (%) and numbers (n). The chi-square test was used to determine differences between categorical variables of interest. Multinomial and binary logistic regression analyses were conducted to investigate the association between categorical variables (dependent) and continuous or categorical ones (independent). During regression analyses, certain demographic variables representing less than 1% of the sample were removed. In addition, monthly family income groups of < 10,000 LKR and 10,000–24,999 LKR were combined together as < 25,000 LKR category. Education level groups of no schooling, primary and secondary education also were combined into a new category as ‘secondary education or below’. The results of logistic regression analyses were reported as odds ratio (OR) and 95% confidence intervals (95%; CI). The p-value was considered significant at <0.05.

      Results

      After removing potential duplicates and incomplete responses, a total of 3707 respondents were recorded before removing <1% categorical groups for analysis. The socio-demographic characteristics of the participants are presented in Table 1. The majority belonged to the 26–30 years age group (24.7%; 913), were females (59.6%; 2209), and had an education level of degree or above (69.1%; 2563). The survey conducted covered all 25 districts in the country with the highest reporting from Colombo (37.8%; 1408) and most of the responders were from rural areas 40.1% (1488). Representation of all ethnic groups was recorded and the majority were Sinhalese (81.9%, 3036). In terms of employment status and monthly income, more than half of the participants were employed (63.0%; 2337), and over a quarter of participants had a monthly income of 50,000–99,000 LKR (26.6%; 986).
      Table 1Sample characteristics
      VariablesTotal (n=3707)
      n%
      Age
       16–25 years82522.3
       26–30 years91324.7
       31–35 years75820.5
       36–40 years49813.5
       >40 years70519.1
      Gender
       Male146839.6
       Female220959.6
       Not specified300.8
      District
       Colombo140337.8
       Gampaha50213.5
       Kandy3529.5
       Kalutara2356.3
       Kurunegala1834.9
       Batticaloa1082.9
       Others92424.9
      Area of residence
       Municipal council area120832.6
       City council area101127.3
       Rural area148840.1
      Ethnicity
       Sinhala303681.9
       Sri Lankan Tamil3048.2
       Indian Tamil571.5
       Sri Lankan Moors2597.0
       Others511.4
      Education level
       No schooling20.1
       Primary education (up to grade 5)00
       Secondary education (up to O/L)1604.3
       Tertiary education (up to A/L)94825.6
       Degree or above256369.1
       Prefer not to say340.9
      Employment status
       Employed233763.0
       Self-employed2005.4
       Unemployed2727.3
       Engaged in home duties1143.1
       Retired from employment551.5
       Full time student or pupil61816.7
       Other842.3
       Prefer not to say270.7
      Monthly family income (in LKR)
       Less than 10,000892.3
       10,000–24,9992316.2
       25,000–49,99960516.3
       50,000–99,99998626.6
       100,000–199,99988723.9
       >200,00090924.5
      Table 2 presents the associations between demographic variables and the frequency of taking nutritional supplements. Participants who never take supplements were 27.4% (1015) whereas rarely, occasionally, and regularly reported 14.5% (538), 32.6% (1210) and 25.5% (944) respectively. Among all the demographic variables, age, gender, ethnicity, employment status and monthly family income of the respondents indicated strong significant associations with the four frequencies of supplementation intake from taking it regularly, occasionally, rarely, or never (p < 0.05). The regression analysis among regular supplement intake by demographic variables was reported in Supplementary Table 1. The odds of regular intake of supplements are lower in all ages compared to the oldest group. Moreover, participants from 31-35 years age group reported significantly lower intake of supplements compared to older > 40 years age category (OR:0.604; 95% CI, 0.451–0.809; p = 0.001). In addition, males were less likely to have regular supplement intake (OR:0.589; 95% CI, 0.485–0.716; p < 0.001) compared to the female counterpart. However, a clear significant difference of regular supplement intake was seen among participants who earned more than > 200,000 LKR when compared with < 25,000 LKR (OR: 0.506; 95% CI, 0.336–0.761; p < 0.001).
      Table 2Association between demographic variables and frequency of taking nutritional supplements
      VariablesRegularlyOccasionallyRarelyNeverp-value
      n (%)n (%)n (%)n (%)
      Total944 (25.5)1210 (32.6)538 (14.5)1015 (27.4)
      Age
       16–25 years176 (21.3)301 (36.5)137 (16.6)211 (25.6)<0.001
       26–30 years225 (24.6)307 (33.6)144 (15.8)237 (26.0)
       31–35 years182 (24.0)234 (30.9)105 (13.9)237 (31.3)
       36–40 years139 (27.9)170 (34.1)51 (10.2)138 (27.7)
       >40 years220 (31.2)195 (27.7)100 (14.2)190 (27.0)
      Gender
       Male334 (22.8)436 (29.7)213 (14.5)485 (33.0)<0.001
       Female600 (27.2)767 (34.7)318 (14.4)524 (23.7)
      District
       Colombo377 (26.9)440 (31.4)187 (13.3)399 (28.4)0.082
       Gampaha129 (25.7)163 (32.5)83 (16.5)127 (25.3)
       Kandy85 (24.1)118 (33.5)46 (13.1)103 (29.3)
       Kalutara55 (23.4)84 (35.7)39 (16.6)57 (24.3)
       Kurunegala42 (23.0)64 (35.0)20 (10.9)57 (31.1)
       Batticaloa16 (14.8)35 (32.4)27 (25.0)30 (27.8)
       Others240 (26.0)306 (33.1)136 (14.7)242 (26.2)
      Area of residence
       Municipal council area311 (25.7)393 (32.5)171 (14.2)333 (27.6)0.939
       City council area244 (24.1)333 (32.9)155 (15.3)279 (27.6)
       Rural area389 (26.1)484 (32.5)212 (14.2)403 (27.1)
      Ethnicity
       Sinhala827 (27.2)1015 (33.4)411 (13.5)783 (25.8)0.001
       Sri Lankan Tamil61 (20.1)82 (27.0)52 (17.1)109 (35.9)
       Indian Tamil8 (14.0)23 (40.4)9 (15.8)17 (29.8)
       Sri Lankan Moors36 (13.9)73 (28.2)60 (23.2)90 (34.7)
       Others12 (23.5)17 (33.3)6 (11.8)16 (31.4)
      Education level
       Secondary education or below25 (15.6)68 (42.5)23 (14.4)44 (27.5)0.056
       Tertiary education249 (26.3)313 (33.0)134 (14.1)252 (26.6)
       Degree or above663 (25.9)815 (31.8)378 (14.7)707 (27.6)
      Employment status
       Employed610 (26.1)735 (31.5)333 (14.2)659 (28.2)0.021
       Self-employed52 (26.0)67 (33.5)24 (12.0)57 (28.5)
       Unemployed72 (26.5)88 (32.4)32 (11.8)80 (29.4)
       Engaged in home duties30 (26.3)35 (30.7)23 (20.2)26 (22.8)
       Retired from employment20 (36.4)15 (27.3)8 (14.5)12 (21.8)
       Full time student or pupil133 (21.5)224 (36.2)111 (18.0)150 (24.3)
       Other18 (21.4)36 (42.9)6 (7.1)24 (28.6)
      Monthly family income (in LKR)
       < 25,00064 (20.0)88 (27.5)47 (14.7)121 (37.8)<0.001
       25,000–49,999144 (23.8)221 (36.5)94 (15.5)146 (24.1)
       50,000–99,999244 (24.7)340 (34.5)153 (15.5)249 (25.3)
       100,000–199,999233 (26.3)288 (32.5)129 (14.5)237 (26.7)
       >200,000259 (28.5)273 (30.0)115 (12.7)262 (28.8)
      Table 3a, Table 3ba and 3b present the vitamins and multivitamin users during the COVID-19 pandemic respectively. The usage of vitamin C, vitamin D and multivitamin among the participants were 46.0% (1288), 8.6% (241), and 10.8% (302) respectively. As seen in Table 3a, Table 3ba, vitamin D, and multivitamin intake had a significant association with age (p < 0.05). Overall females were more likely to take vitamin C supplementation (OR: 1.325; 95% CI, 1.120–1.567; p < 0.001) when compared to males. A strong significant correlation resulted between all districts and areas of residence with supplementation (p < 0.001). Odds ratio presented in Table 3a, Table 3bb exhibited the district of Kandy had a less likelihood for intake of vitamin C (OR: 0.541; 95% CI, 0.0393–0.743); p < 0.001) and vitamin D (OR: 0.376; 95% CI, 0.201–0.700; p = 0.002) compared to Colombo district. Furthermore, the odds of a lower intake in the rural area were seen across all supplements especially with vitamin D (OR: 0.552; 95% CI, 0.394–0.774; p = 0.001) and multivitamin (OR: 0.570; 95% CI, 0.420–0.774); p < 0.001). Regarding the ethnicity, there was no association shown except for Sri Lankan Tamils indicating the lowest intake of vitamin C supplementation (OR: 0.558; 95% CI, 0.405–0.7688; p < 0.001) when compared to the Sinhala ethnicity group. Moreover, at all education levels supplements vitamin C, D and multivitamin demonstrated significant correlations (Table 3a, Table 3b). Analysis results of participants of tertiary education presented in Table 3b, were found more likely to take vitamin C (OR: 1.585; 95% CI, 1.054–2.384; p = 0.027) supplements when compared to those lower education levels. Employment status had a strong association with vitamin D and multivitamin intake (Table 3a). Monthly family income played a significant relationship with supplement intake, with participants earning >200,000 LKR more likely to take vitamin D (OR: 1.899; 95% CI, 1.034–3.490; p = 0.039) and multivitamin supplementation (OR: 3.222; 95% CI, 1.737–5.977; p < 0.001) when compared to the least earning category.
      Table 3aUsage of vitamins and multivitamin among the supplement users during the COVID-19 pandemic
      VariablesVitamin CVitamin DMultivitamin
      n (%)p-valuen (%)p-valuen (%)p-value
      Total1288 (46.0)241 (8.6)302 (10.8)
      Age
       16–25 years257 (43.3)0.27727 (4.6)<0.00137 (6.2)˂0.001
       26–30 years333 (47.6)58 (8.3)72 (10.3)
       31–35 years272 (44.7)46 (7.6)69 (11.3)
       36–40 years198 (49.6)39 (9.8)55 (13.8)
       >40 years224 (45.3)70 (14.1)69 (13.9)
      Gender
       Male432 (40.6)0.00186 (8.1)0.48897 (9.1)0.026
       Female843 (49.1)152 (8.8)203 (11.8)
      District
       Colombo476 (47.8)0.001126 (12.7)0.001144 (14.5)0.001
       Gampaha204 (48.3)45 (10.7)54 (12.8)
       Kandy114 (35.5)12 (3.7)22 (6.9)
       Kalutara102 (52.3)18 (9.2)15 (7.7)
       Kurunegala66 (41.0)8 (5.0)11 (6.8)
       Batticaloa6 (60.0)1 (10.0)0 (0.0)
       Others320 (46.0)31 (4.5)56 (8.0)
      Area of residence
       Municipal council area368 (49.4)0.01391 (12.2)0.001107 (14.4)0.001
       City council area349 (47.7)76 (10.4)105 (14.3)
       Rural area571 (43.1)74 (5.6)90 (6.8)
      Ethnicity
       Sinhala1213 (46.3)0.445230 (8.8)0.673284 (10.8)0.668
       Sri Lankan Tamil21 (43.8)4 (8.3)7 (14.6)
       Indian Tamil6 (27.3)1 (4.5)1 (4.5)
       Sri Lankan Moors37 (42.5)4 (4.6)7 (8.0)
       Others11 (45.8)2 (8.3)3 (12.5)
      Education level
       Secondary education or below48 (35.0)0.0185 (3.6)0.0149 (6.6)0.001
       Tertiary education383 (48.1)58 (7.3)55 (6.9)
       Degree or above848 (46.0)178 (9.7)237 (12.9)
      Employment status
       Employed837 (47.2)0.486167 (9.4)0.001199 (11.2)0.006
       Self-employed61 (40.9)9 (6.0)21 (14.1)
       Unemployed97 (44.5)19 (8.7)21 (9.6)
       Engaged in home duties47 (50.0)10 (10.6)18 (19.1)
       Retired from employment17 (45.9)8 (21.6)3 (8.1)
       Full time student or pupil194 (43.6)17 (3.8)29 (6.5)
       Other24 (39.3)7 (11.5)7 (11.5)
      Monthly family income (in LKR)
       < 25,00082 (36.4)0.00511 (4.9)0.0017 (3.1)0.001
       25,000–49,999218 (42.9)30 (5.9)25 (4.9)
       50,000–99,999384 (49.7)48 (6.2)66 (8.5)
       100,000–199,999302 (45.8)63 (9.5)99 (15.0)
       >200,000302 (47.6)89 (14.0)105 (16.5)
      Table 3bOdds (OR) of vitamins and multivitamins usage among the supplement users by socio-demographic variables
      VariablesVitamin CVitamin DMultivitamin
      OR (95% CI)p-valueOR (95% CI)p-valueOR (95% CI)p-value
      Age
       16–25 years
      Reference variable.
      111
       26–30 years0.981 (0.718–1.342)0.9070.994 (0.607–1.628)0.9821.123 (0.712–1.771)0.619
       31–35 years0.899 (0.642–1.258)0.5330.802 (0.470–1.367)0.4171.282 (0.790–2.083)0.315
       36–40 years1.031 (0.717–1.482)0.8701.046 (0.608–1.800)0.8721.232 (0.741–2.048)0.421
       >40 years0.828 (0.587–1.168)0.2821.590 (0.962–2.630)0.0711.369 (0.843–2.224)0.204
      Gender
       Male
      Reference variable.
      111
       Female1.325 (1.120–1.567)0.0011.300 (1.009–1.677)0.0431.280 (1.015–1.615)0.037
      District
       Colombo
      Reference variable.
      111
       Gampaha0.950 (0.730–1.236)0.7010.813 (0.561–1.176)0.2710.946 (0.676–1.324)0.747
       Kandy0.541 (0.393–0.743)<0.0010.376 (0.201–0.700)0.0020.725 (0.448–1.174)0.191
       Kalutara0.976 (0.691–1.379)0.8910.861 (0.525–1.414)0.5550.562 (0.330–0.958)0.034
       Kurunegala0.841 (0.564–1.252)0.3930.500 (0.242–1.035)0.0620.787 (0.429–1.446)0.441
       Batticaloa0.976 (0.585–1.628)0.9270.707 (0.297–1.681)0.4330.672 (0.302–1.494)0.330
       Others0.773 (0.618–0.969)0.0250.403 (0.275–0.590)<0.0010.672 (0.490–0.992)0.014
      Area of residence
       Municipal council area
      Reference variable.
      111
       City council area0.956 (0.776–1.179)0.6770.761 (0.572–1.012)0.0600.936 (0.723–1.212)0.618
       Rural area0.803 (0.647–0.997)0.0470.552 (0.394–0.774)0.0010.570 (0.420–0.774)<0.001
      Ethnicity
       Sinhala
      Reference variable.
      111
       Sri Lankan Tamil0.558 (0.405–0.768)<0.0010.963 (0.580–1.600)0.8840.880 (0.556–1.393)0.585
       Indian Tamil0.567 (0.303–1.061)0.0760.706 (0.263–1.893)0.4881.364 (0.636–2.925)0.425
       Sri Lankan Moors0.759 (0.547–1.054)0.0990.682 (0.394–1.181)0.1721.007 (0.639–1.586)0.976
       Others1.393 (0.649–2.992)0.3951.325 (0.563–3.120)0.5202.098 (0.982–4.480)0.056
      Education level
       Secondary education or below
      Reference variable.
      111
       Tertiary education1.585 (1.054–2.384)0.0270.769 (0.388–1.525)0.4520.810 (0.420–1.565)0.531
       Degree or above1.142 (0.758–1.720)0.5250.716 (0.363–1.413)0.3361.167 (0.610–2.232)0.642
      Employment status
       Employed
      Reference variable.
      111
       Self-employed0.730 (0.514–1.038)0.0801.126 (0.683–1.859)0.6411.746 (1.127–2.706)0.013
       Unemployed0.899 (0.649–1.247)0.5241.163 (0.704–1.921)0.5541.312 (0.814–2.113)0.265
       Engaged in home duties0.676 (0.433–1.057)0.0860.823 (0.419–1.616)0.5711.509 (0.864–2.637)0.148
       Retired from employment0.637 (0.338–1.203)0.1641.943 (0.957–3.943)0.0661.105 90.484–2.522)0.812
       Full time student or pupil0.852 (0.611–1.188)0.3450.755 (0.429–1.328)0.3291.519 (0.935–2.468)0.092
       Other1.097 (0.642–1.874)0.7351.693 (0.846–3.387)0.1371.749 (0.879–3.481)0.111
      Monthly family income (in LKR)
       <25,000
      Reference variable.
      111
       25,000–49,9990.966 (0.688–1.355)0.8400.844 (0.442–1.612)0.6081.173 (0.610–2.256)0.632
       50,000–99,9991.309 (0.943–1.816)0.1070.895 (0.486–1.646)0.7211.729 90.940–3.181)0.078
       100,000–199,9991.008 (0.716–1.421)0.9621.341 (0.731–2.458)0.3432.787 (1.513–5.133)0.001
       >200,0001.241 90.869–1.772)0.2341.899 (1.034–3.490)0.0393.222 (1.737–5.977)<0.001
      Reference variable.
      The usage of non-vitamin supplements across the participants to enhance the immune system is shown inSupplementary Table 2a and 2b. A majority of the participants (59.5%) consumed kothamalli, while other supplements used were Ayurvedic products (26.0%; 729), herbal products (10.9%; 306) homemade remedies (16.4%; 459), and syrups (1.3%; 36). Age, area of residence, education level, and employment status showed no associations with the intake of non-vitamin supplements. In regards to gender, females tend to use kothamalli more (OR: 1.324; 95% CI, 1.096–1.599; p = 0.004) than males. Intake of kothamalli and homemade remedies demonstrated a significant association between districts (p < 0.001) (Supplementary Table 2a). In Supplementary Table 2b, the participants from the district of Kandy showed a significantly higher intake of kothamalli (OR: 1.773; 95% CI, 0.182–2.659; p = 0.006) in contrast to participants from the Colombo district. Additionally, the likelihood of making homemade remedies was significantly higher in Kurunegala (OR: 2.481; 95% CI, 1.626–3.786; p < 0.001) and Batticaloa (OR: 1.857; 95% CI, 1.101–3.132; p = 0.020). The ethnic categories had a significant association with the consumption of kothamalli and Ayurvedic products (p <0.001; p = 0.006). In comparison, all other ethnicities significantly had a lower intake of both kothamalli and Ayurvedic products than Sinhala. Nonetheless, both Sri Lankan Tamils (OR: 2.268; 95% CI, 1.629–3.158; p < 0.001) and Indian Tamils (OR: 2.243; 95% CI, 1.174–4.285; p = 0.041) and as well as Sri Lankan Moors (OR:1.886; 95% CI, 1.333–2.670; p < 0.001) were most likely to make their own remedies at home compared to Sinhalese (Supplementary Table 2b). Monthly income had a significant association with kothamalli (p < 0.001) and ayurvedic products (p = 0.002) intake, of which Ayurvedic products was more likely to be consumed by participants earning 100,000–199,999 LKR (OR: 1.794; 95% CI, 1.208–2.665; p = 0.004) and 50,000–99,000 LKR (OR: 1.623; 95% CI, 1.109–2.376; p = 0.013) than the other income groups.
      The most commonly used main ingredients in homemade remedies are displayed in Figure 1. Majority of the participants used coriander (57%; 629) and ginger (20%; 217) as main ingredients. Other commonly used ingredients were lime (4%; 49), garlic (4%; 48), lemon (3%; 37), turmeric (2%; 26) and pepper (2%; 20). The remaining 8% (87) belonged to the other group which mostly consisted of mixtures of herbs and other natural products.
      Figure 1
      Figure 1Common main ingredients used in home-made remedies.

      Discussion

      Sri Lanka was experiencing the highest number of COVID-19-infected patients and fatalities throughout the study period. Due to the limited vaccine coverage in Sri Lanka, alternative immunity-enhancing products have taken the attention of the general public. This online survey conducted explored various immunity-enhancing products during COVID-19, from nutritional supplements to many other natural products including herbs in Sri Lanka. Only a quarter of our survey respondents did not take any nutritional supplements to strengthen the immunity. Despite the fact that our study sample consisted mostly of young and educated people, we received a large number of responses from diverse ethnic groups and throughout all districts of the island, making our survey population a fair reflection of Sri Lanka. The survey showcased frequencies of supplement intake to have significant differences across the various ethnicities, this is due to the difference in beliefs and practices belonging to the specific ethnic group. A similar study conducted in Benha city, Egypt during COVID-19 reported the use of vitamin C (27%), vitamin D (17.7%), immune-boosting drinks (39.3%), honey (32.2%), and garlic (37.2%) amidst the participants [
      • Khabour O.F.
      • Hassanein S.F.M.
      Use of vitamin/zinc supplements, medicinal plants, and immune boosting drinks during COVID-19 pandemic: a pilot study from Benha city, Egypt.
      ]. In Italy, most believed that strengthening immune defences through nutrition elements enhances the function of the immune system to reduce the risk of COVID-19 infection [
      • Savarese M.
      • Castellini G.
      • Morelli L.
      • Graffigna G.
      COVID-19 disease and nutritional choices: How will the pandemic reconfigure our food psychology and habits? A case study of the Italian population.
      ].
      In this study, various demographic factors were associated with the frequency of nutritional supplement intake. Regular supplement intake was seen greater among the older (>40 years) participants in contrast to the younger counterpart. A similar pattern was observed in Bangladesh, where elderly individuals were more likely to take preventive supplements (OR: 2.93; 95% CI, 1.37–6.30; p = 0.004) [
      • Ahmed I.
      • Hasan M.
      • Akter R.
      • Sarkar B.K.
      • Rahman M.
      • Sarker M.S.
      • et al.
      Behavioral preventive measures and the use of medicines and herbal products among the public in response to COVID-19 in Bangladesh: a cross-sectional study.
      ]. Older age and/or existing co-morbidities are an increased risk factor for severe COVID-19 infection compared to the younger age group which may also cause elders to take extra measures to be more careful [
      • Gao Y dong
      • Ding M.
      • Dong X.
      • Zhang J jin
      • Kursat Azkur A.
      • Azkur D.
      • et al.
      Risk factors for severe and critically ill COVID-19 patients: a review.
      ]. Higher intake of supplementation was also mostly seen across females than males. Our gender analysis results reflect similar patterns as of the online study among Polish adults [
      • Hamulka J.
      • Jeruszka-Bielak M.
      • Górnicka M.
      • Drywień M.E.
      • Zielinska-Pukos M.A.
      Dietary supplements during COVID-19 outbreak. Results of Google trends analysis supported by PLifeCOVID-19 online studies.
      ]. A study which was conducted among Google users across multiple countries to investigate their interests in nutritional supplements during the COVID-19 pandemic period revealed that, the difference of interest was either because of traditional medicine knowledge or regional beliefs in the specific country [
      • Günalan E.
      • Cebioğlu İ.K.
      • Ö Çonak
      The popularity of the biologically-based therapies during coronavirus pandemic among the Google users in the USA, UK, Germany, Italy and France.
      ]. Consistently, the difference between the ethnic groups indicates they do not share the same knowledge and attitudes on supplements use [
      • Adegboye A.R.A.
      • Ojo O.
      • Begum G.
      The use of dietary supplements among African and Caribbean women living in the UK: a cross-sectional study.
      ]. The lower-earning category of participants was significantly less likely to use supplements considering the supplements tend to be more expensive [
      • Cowan A.E.
      • Jun S.
      • Gahche J.J.
      • Tooze J.A.
      • Dwyer J.T.
      • Eicher-Miller H.A.
      • et al.
      Dietary supplement use differs by socioeconomic and health-related characteristics among U.S. adults, NHANES 2011–2014.
      ]. These results are similar to investigations done in other countries that have indicated supplement intake is greater among the high-income populations [
      • Tsang S.N.
      • Herbold N.H.
      • Pycz L.
      Dietary supplement use among active multi-ethnic adults.
      ,
      • Fennell D.
      Determinants of supplement usage.
      ]. Since a greater proportion of our participants were educated, there was no difference in supplement intake found. Whereas other related studies during COVID-19 discovered such preventive behaviours were higher among educated participants [
      • Ahmed I.
      • Hasan M.
      • Akter R.
      • Sarkar B.K.
      • Rahman M.
      • Sarker M.S.
      • et al.
      Behavioral preventive measures and the use of medicines and herbal products among the public in response to COVID-19 in Bangladesh: a cross-sectional study.
      ,
      • Hamulka J.
      • Jeruszka-Bielak M.
      • Górnicka M.
      • Drywień M.E.
      • Zielinska-Pukos M.A.
      Dietary supplements during COVID-19 outbreak. Results of Google trends analysis supported by PLifeCOVID-19 online studies.
      ].
      In this study, a larger proportion (46.0%; 1288) used vitamin C supplements, which have been studied to stimulate various defense mechanisms including antimicrobial and immunomodulatory properties [
      • Leibovitz B.
      • Siegel B v
      Ascorbic acid, neutrophil function, and the immune response.
      ]. Nonetheless, a review on therapeutic vitamin C supplementation had no consistent effect on the severity and the duration of the common cold [
      • Hemilä H.
      • Chalker E.
      Vitamin C for preventing and treating the common cold.
      ]. A study in the USA with COVID-19 patients, were administered high doses of ascorbic acid and had no significant decrease of symptoms in comparison to standard care (p = 0.25) [
      • Thomas S.
      • Patel D.
      • Bittel B.
      • Wolski K.
      • Wang Q.
      • Kumar A.
      • et al.
      Effect of high-dose zinc and ascorbic acid supplementation vs usual care on symptom length and reduction among ambulatory patients with SARS-CoV-2 infection: the COVID A to Z randomized clinical trial.
      ]. Contrarily, vitamin D and multivitamin supplementation intakes were higher among participants who were older, employed, and from affluent categories. Vitamin D and multivitamin supplementation are recommended as these can be effective, especially among individuals who are either deficient and in self-isolation or have bad dietary practices [
      • Jayawardena R.
      • Sooriyaarachchi P.
      • Chourdakis M.
      • Jeewandara C.
      • Ranasinghe P.
      Enhancing immunity in viral infections, with special emphasis on COVID-19: a review.
      ]. Furthermore, another study exploring dietary supplements effect on COVID-19 recorded lower risk of infection in participants taking multivitamins by 13% (OR = 0.87; p < 0.001.) and vitamin D by 9% (OR = 0.91; p < 0.001) [
      • Louca P.
      • Murray B.
      • Klaser K.
      • Graham M.S.
      • Mazidi M.
      • Leeming E.R.
      • et al.
      Modest effects of dietary supplements during the COVID-19 pandemic: Insights from 445 850 users of the COVID-19 symptom study app.
      ]. As vitamin D deficiency has been associated with COVID-19 mortality rate in the Asian region, vitamin D supplementation could have a vital role in the prevention or treatment of the disease [
      • Jayawardena R.
      • Jeyakumar D.T.
      • Francis T.v.
      • Misra A.
      Impact of the vitamin D deficiency on COVID-19 infection and morality in Asian countries.
      ,
      • Sooriyaarachchi P.
      • Jeyakumar D.T.
      • King N.
      • Jayawardena R.
      Impact of vitamin D deficiency on COVID-19.
      ]. Accordingly, vitamin D supplementation was administered among elderly patients in France with COVID-19 and were less likely to exhibit severity (OR = 0.46; 95% CI, 0.01–0.81; p = 0.033) [
      • Annweiler G.
      • Corvaisier M.
      • Gautier J.
      • Dubée V.
      • Legrand E.
      • Sacco G.
      • et al.
      Vitamin d supplementation associated to better survival in hospitalized frail elderly COVID-19 patients: The Geria-COVID quasi-experimental study.
      ]. In comparison to these micronutrient supplements, other immunity enhancing products reported association with various factors; residing location and ethnicity which may have influenced by cultural practices and beliefs [
      • Bishop F.L.
      • Yardley L.
      • Lewith G.T.
      A systematic review of beliefs involved in the use of complementary and alternative medicine.
      ]. Besides, the use of such herbs and products was high probably due to the immediate availability in most households in Sri Lanka. Positive previous experiences with herbal therapy, as well as family traditions and practices, were among the most regularly mentioned reasons for the preferred use of herbal medicine in a focus group study in Germany [
      • Welz A.N.
      • Emberger-Klein A.
      • Menrad K.
      Why people use herbal medicine: insights from a focus-group study in Germany.
      ].
      Herbs and spices have been extensively studied around the world due to their greater demand for its natural food antioxidant and antimicrobial activity [
      • Embuscado M.E.
      Spices and herbs: natural sources of antioxidants – a mini review.
      ]. The majority (59.5%) of participants in our study took kothamalli to enhance their immunity. Coriander, has a long history as a traditional medicine, although a review investigating its bioactive constituents reported no effectiveness when treated for respiratory ailments such as asthma or bronchiolitis [
      • Laribi B.
      • Kouki K.
      • M’Hamdi M.
      • Bettaieb T.
      Coriander (Coriandrum sativum L.) and its bioactive constituents.
      ]. In Bangladesh, 57.6% proportion recorded the use of herbal foods to lower the risk of COVID-19 [
      • Ahmed I.
      • Hasan M.
      • Akter R.
      • Sarkar B.K.
      • Rahman M.
      • Sarker M.S.
      • et al.
      Behavioral preventive measures and the use of medicines and herbal products among the public in response to COVID-19 in Bangladesh: a cross-sectional study.
      ]. Additionally, a Saudi population study revealed approximately 44.8% of the participants used herbs and natural products daily as a protective measure with a significant increase of intake after COVID-19 [
      • Abdullah Alotiby A.
      • Naif Al-Harbi L.
      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.
      ]. Similarly, use of herbal products among patients were prevalent in the case of the previous infectious MERS outbreak in South Korea reporting 76.1% of patients used one or more type of herbal products [
      • Hwang J.H.
      • Cho H.J.
      • Im H bin
      • Jung Y.S.
      • Choi S.J.
      • Han D.
      Complementary and alternative medicine use among outpatients during the 2015 MERS outbreak in South Korea: a cross-sectional study.
      ]. Home-made remedies were made including various herbs and natural products, the commonly used ingredients were coriander, ginger, lime, garlic and lemon. In Morocco as well, garlic, and ginger were among the frequently consumed natural products during the pandemic [
      • Alami A el
      • Fattah A.
      • Chait A.
      Medicinal plants used for the prevention purposes during the COVID-19 pandemic in Morocco.
      ]. Previous studies have reported that such ingredients could help in boosting an individual's immunity and may strengthen the immune system in general but just not related to the COVID-19 infection [
      • Sultan M.T.
      • Buttxs M.S.
      • Qayyum M.M.N.
      • Suleria H.A.R.
      Immunity: plants as effective mediators.
      ,
      • Elmowalid G.A.
      • Abd El-Hamid M.I.
      • Abd El-Wahab A.M.
      • Atta M.
      • Abd El-Naser G.
      • Attia A.M.
      Garlic and ginger extracts modulated broiler chicks innate immune responses and enhanced multidrug resistant Escherichia coli O78 clearance.
      ,
      • Wang K.
      • Conlon M.
      • Ren W.
      • Chen B.B.
      • Bączek T.
      Natural products as targeted modulators of the immune system.
      ].
      The current study has some limitations. Self-reported weight and height values in this study population were inaccurate therefore BMI values were not utilised, a previous study conducted in Sri Lankan adults showed only one-fourth can report weight and height accurately [
      • Jayawardena R.
      • Byrne N.M.
      • Soares M.J.
      • Katulanda P.
      • Hills A.P.
      Body weight perception and weight loss practices among Sri Lankan adults.
      ]. The questions asked regarding immunity enhancing supplements, only included the type and frequency of supplements but the doses are key. For instance, vitamin D supplementation at a dose of 5000IU per day is found to be more effective [
      • Jayawardena R.
      • Sooriyaarachchi P.
      • Chourdakis M.
      • Jeewandara C.
      • Ranasinghe P.
      Enhancing immunity in viral infections, with special emphasis on COVID-19: a review.
      ]. Moreover, not all multivitamins contain all the required vitamins and minerals as some may contain limited ingredients. A few of our questions were vague and overlapping. In the case of distinction between herbs and Ayurvedic products, as kothamalli/coriander is usually suggested under Ayurveda. In spite of the limitations, the main aim of this study was to report the types of supplements and the frequency of intake among the general public. Most countries studied similar patterns of usage frequency across various nutritional supplements [
      • Abdullah Alotiby A.
      • Naif Al-Harbi L.
      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.
      ,
      • Ahmed I.
      • Hasan M.
      • Akter R.
      • Sarkar B.K.
      • Rahman M.
      • Sarker M.S.
      • et al.
      Behavioral preventive measures and the use of medicines and herbal products among the public in response to COVID-19 in Bangladesh: a cross-sectional study.
      ,
      • Hamulka J.
      • Jeruszka-Bielak M.
      • Górnicka M.
      • Drywień M.E.
      • Zielinska-Pukos M.A.
      Dietary supplements during COVID-19 outbreak. Results of Google trends analysis supported by PLifeCOVID-19 online studies.
      ,
      • Khabour O.F.
      • Hassanein S.F.M.
      Use of vitamin/zinc supplements, medicinal plants, and immune boosting drinks during COVID-19 pandemic: a pilot study from Benha city, Egypt.
      ]. These data are critical for making informed policy decisions at the national level. There are false claims and some products may have adverse effects on human health. Furthermore, some supplements may be overly expensive. The primary objectives of COVID-19 preventive measures are to follow public health guidelines, a balanced diet and daily physical movement. If deficiencies are present, nutritional supplementation may deem to be beneficial.

      Conclusion

      This study explored the proportion of Sri Lankans using nutrition supplements such as micronutrients, herbs, and other natural products to enhance their immunity during the COVID-19 pandemic. Nearly three quarter of the population take micronutrient supplements to enhance immunity. Age, gender, residing district, and income groups are strongly associated with supplement intake. A significant proportion of the participants takes non-evidence based vitamins such as vitamin C and herbs such as coriander in Sri Lanka.

      Funding statement

      This research study did not receive any funding.

      Conflicts of interest

      The authors declare that they have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

      Author contributions

      RJ, TVF, PS conceived and designed the online survey questionnaire; disseminated the questionnaire; PS analysed and interpreted the data, TVF and RJ drafted the manuscript. PS revised the manuscript. All authors read and approved the final manuscript.

      Acknowledgements

      The authors would express our gratitude towards every participant for their contribution in conducting this research study.

      Appendix ASupplementary data

      The following are the Supplementary data to this article:

      References

        • Kaswa R.
        • Govender I.
        Novel coronavirus pandemic: a clinical overview.
        South African Family Practice. 2020; 62: 1-5https://doi.org/10.4102/safp.v62i1.5123
      1. (COVID Live Update: 171,084,997 Cases and 3,557,998 Deaths from the Coronavirus – Worldometer 2021.)
        https://www.worldometers.info/coronavirus/
        Date: 2021
        Date accessed: May 31, 2021
        • Wiersinga W.J.
        • Rhodes A.
        • Cheng A.C.
        • Peacock S.J.
        • Prescott H.C.
        Pathophysiology, transmission, diagnosis, and treatment of coronavirus disease 2019 (COVID-19): a review.
        JAMA. 2020; 324: 782-793https://doi.org/10.1001/jama.2020.12839
        • Pascarella G.
        • Strumia A.
        • Piliego C.
        • Bruno F.
        • del Buono R.
        • Costa F.
        • et al.
        COVID-19 diagnosis and management: a comprehensive review.
        J Intern Med. 2020; 288: 192-206https://doi.org/10.1111/joim.13091
        • Ahn D.G.
        • Shin H.J.
        • Kim M.H.
        • Lee S.
        • Kim H.S.
        • Myoung J.
        • et al.
        Current status of epidemiology, diagnosis, therapeutics, and vaccines for novel coronavirus disease 2019 (COVID-19).
        J Microbiol Biotechnol. 2020; 30: 313-324https://doi.org/10.4014/jmb.2003.03011
        • Jean S.S.
        • Lee P.I.
        • Hsueh P.R.
        Treatment options for COVID-19: the reality and challenges.
        J Microbiol Immunol Infect. 2020; 53: 436-443https://doi.org/10.1016/j.jmii.2020.03.034
        • Ma Q.X.
        • Shan H.
        • Zhang H.L.
        • Li G.M.
        • Yang R.M.
        • Chen J.M.
        Potential utilities of mask-wearing and instant hand hygiene for fighting SARS-CoV-2.
        J Med Virol. 2020; 92: 1567-1571https://doi.org/10.1002/jmv.25805
        • Chung J.Y.
        • Thone M.N.
        • Kwon Y.J.
        COVID-19 vaccines: the status and perspectives in delivery points of view.
        Adv Drug Deliv Rev. 2021; 170: 1-25https://doi.org/10.1016/j.addr.2020.12.011
        • Chung Y.H.
        • Beiss V.
        • Fiering S.N.
        • Steinmetz N.F.
        COVID-19 vaccine frontrunners and their nanotechnology design.
        ACS Nano. 2020; 14: 12522-12537https://doi.org/10.1021/acsnano.0c07197
      2. Unequal Vaccine distribution self-defeating, world health organization chief tells economic and social council’s special ministerial meeting - World | ReliefWeb. 2021
        • Pecora F.
        • Persico F.
        • Argentiero A.
        • Neglia C.
        • Esposito S.
        The role of micronutrients in support of the immune response against viral infections.
        Nutrients. 2020; 12: 1-45https://doi.org/10.3390/nu12103198
        • Jayawardena R.
        • Misra A.
        Balanced diet is a major casualty in COVID-19. Diabetes and Metabolic Syndrome.
        Clin Res Rev. 2020; 14: 1085-1086https://doi.org/10.1016/j.dsx.2020.07.001
        • Iddir M.
        • Brito A.
        • Dingeo G.
        • del Campo S.S.F.
        • Samouda H.
        • la Frano M.R.
        • et al.
        Strengthening the immune system and reducing inflammation and oxidative stress through diet and nutrition: considerations during the COVID-19 crisis.
        Nutrients. 2020; 12https://doi.org/10.3390/nu12061562
        • Chandra R.K.
        Protein-energy malnutrition and immunological responses.
        J Nutr. 1992; 122 (Oxford Academic): 597-600https://doi.org/10.1093/jn/122.suppl_3.597
        • Gopalan H.S.
        • Misra A.
        • Jayawardena R.
        Nutrition and diabetes in South Asia.
        Eur J Clin Nutr. 2018; 72: 1267-1273https://doi.org/10.1038/s41430-018-0219-6
        • Jayawardena R.
        • Sooriyaarachchi P.
        • Chourdakis M.
        • Jeewandara C.
        • Ranasinghe P.
        Enhancing immunity in viral infections, with special emphasis on COVID-19: a review.
        Diab Metab Synd Clin Res Rev. 2020; 14: 367-382https://doi.org/10.1016/j.dsx.2020.04.015
        • Kamarli Altun H.
        • Karacil Ermumcu M.S.
        • Seremet Kurklu N.
        Evaluation of dietary supplement, functional food and herbal medicine use by dietitians during the COVID-19 pandemic.
        Pub Health Nutr. 2021; 24: 861-869https://doi.org/10.1017/S1368980020005297
        • Sultan M.T.
        • Buttxs M.S.
        • Qayyum M.M.N.
        • Suleria H.A.R.
        Immunity: plants as effective mediators.
        Crit Rev Food Sci Nutr. 2014; 54: 1298-1308https://doi.org/10.1080/10408398.2011.633249
        • Abdullah Alotiby A.
        • Naif Al-Harbi L.
        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 Pharma J. 2021; https://doi.org/10.1016/j.jsps.2021.04.001
        • Ahmed I.
        • Hasan M.
        • Akter R.
        • Sarkar B.K.
        • Rahman M.
        • Sarker M.S.
        • et al.
        Behavioral preventive measures and the use of medicines and herbal products among the public in response to COVID-19 in Bangladesh: a cross-sectional study.
        PLoS One. 2020; 15https://doi.org/10.1371/journal.pone.0243706
        • Rautiainen S.
        • Manson J.E.
        • Lichtenstein A.H.
        • Sesso H.D.
        Dietary supplements and disease prevention-a global overview.
        Nat Rev Endocrinol. 2016; 12: 407-420https://doi.org/10.1038/nrendo.2016.54
        • Medagama A.B.
        • Bandara R.
        • Abeysekera R.A.
        • Imbulpitiya B.
        • Pushpakumari T.
        Use of complementary and alternative medicines (CAMs) among type 2 diabetes patients in Sri Lanka: a cross sectional survey.
        BMC Complement Alternat Med. 2014; 14: 1-5https://doi.org/10.1186/1472-6882-14-374
        • Sooriyaarachchi Piumika
        • Francis Tormalli V.
        • King Neil
        • Jayawardena R.
        Increased physical inactivity and weight gain during the COVID-19 pandemic in Sri Lanka: an online cross-sectional survey.
        Diab Metabol Synd Clin Res Rev. 2021; ([Under revi])
        • World Medical Association declaration of Helsinki
        Ethical principles for medical research involving human subjects.
        JAMA. 2013; 310 (4): 2191https://doi.org/10.1001/jama.2013.281053
        • Hamulka J.
        • Jeruszka-Bielak M.
        • Górnicka M.
        • Drywień M.E.
        • Zielinska-Pukos M.A.
        Dietary supplements during COVID-19 outbreak. Results of Google trends analysis supported by PLifeCOVID-19 online studies.
        Nutrients. 2021; 13: 1-17https://doi.org/10.3390/nu13010054
        • Khabour O.F.
        • Hassanein S.F.M.
        Use of vitamin/zinc supplements, medicinal plants, and immune boosting drinks during COVID-19 pandemic: a pilot study from Benha city, Egypt.
        Heliyon. 2021; 7: e06538https://doi.org/10.1016/j.heliyon.2021.e06538
        • Savarese M.
        • Castellini G.
        • Morelli L.
        • Graffigna G.
        COVID-19 disease and nutritional choices: How will the pandemic reconfigure our food psychology and habits? A case study of the Italian population.
        Nutr Metab Cardiovas Dis. 2021; 31: 399-402https://doi.org/10.1016/j.numecd.2020.10.013
        • Gao Y dong
        • Ding M.
        • Dong X.
        • Zhang J jin
        • Kursat Azkur A.
        • Azkur D.
        • et al.
        Risk factors for severe and critically ill COVID-19 patients: a review.
        Allergy Eur J Allergy Clin Immunol. 2021; 76: 428-455https://doi.org/10.1111/all.14657
        • Günalan E.
        • Cebioğlu İ.K.
        • Ö Çonak
        The popularity of the biologically-based therapies during coronavirus pandemic among the Google users in the USA, UK, Germany, Italy and France.
        Complement Therap Med. 2021; 58: 102682https://doi.org/10.1016/j.ctim.2021.102682
        • Adegboye A.R.A.
        • Ojo O.
        • Begum G.
        The use of dietary supplements among African and Caribbean women living in the UK: a cross-sectional study.
        Nutrients. 2020; 12https://doi.org/10.3390/nu12030847
        • Cowan A.E.
        • Jun S.
        • Gahche J.J.
        • Tooze J.A.
        • Dwyer J.T.
        • Eicher-Miller H.A.
        • et al.
        Dietary supplement use differs by socioeconomic and health-related characteristics among U.S. adults, NHANES 2011–2014.
        Nutrients. 2018; 10https://doi.org/10.3390/nu10081114
        • Tsang S.N.
        • Herbold N.H.
        • Pycz L.
        Dietary supplement use among active multi-ethnic adults.
        J Am Diet Assoc. 2007; 107: A34https://doi.org/10.1016/j.jada.2007.05.359
        • Fennell D.
        Determinants of supplement usage.
        Prevent Med. 2004; 39: 932-939https://doi.org/10.1016/j.ypmed.2004.03.031
        • Leibovitz B.
        • Siegel B v
        Ascorbic acid, neutrophil function, and the immune response.
        Int J Vitamin Nutr Res. 1978; 48: 159-164
        • Hemilä H.
        • Chalker E.
        Vitamin C for preventing and treating the common cold.
        Cochrane Database Syst Rev. 2013; 2013https://doi.org/10.1002/14651858.CD000980.pub4
        • Thomas S.
        • Patel D.
        • Bittel B.
        • Wolski K.
        • Wang Q.
        • Kumar A.
        • et al.
        Effect of high-dose zinc and ascorbic acid supplementation vs usual care on symptom length and reduction among ambulatory patients with SARS-CoV-2 infection: the COVID A to Z randomized clinical trial.
        JAMA Network Open. 2021; 4 (e210369): e210369https://doi.org/10.1001/jamanetworkopen.2021.0369
        • Louca P.
        • Murray B.
        • Klaser K.
        • Graham M.S.
        • Mazidi M.
        • Leeming E.R.
        • et al.
        Modest effects of dietary supplements during the COVID-19 pandemic: Insights from 445 850 users of the COVID-19 symptom study app.
        BMJ Nutr Prevent Health. 2021; (bmjnph-2021-000250)https://doi.org/10.1136/bmjnph-2021-000250
        • Jayawardena R.
        • Jeyakumar D.T.
        • Francis T.v.
        • Misra A.
        Impact of the vitamin D deficiency on COVID-19 infection and morality in Asian countries.
        Diabetes and Metabolic Syndrome: Clinical Research and Reviews. 2021; 15: 757-764https://doi.org/10.1016/j.dsx.2021.03.006
        • Sooriyaarachchi P.
        • Jeyakumar D.T.
        • King N.
        • Jayawardena R.
        Impact of vitamin D deficiency on COVID-19.
        Clin Nutr ESPEN. 2021; https://doi.org/10.1016/j.clnesp.2021.05.011
        • Annweiler G.
        • Corvaisier M.
        • Gautier J.
        • Dubée V.
        • Legrand E.
        • Sacco G.
        • et al.
        Vitamin d supplementation associated to better survival in hospitalized frail elderly COVID-19 patients: The Geria-COVID quasi-experimental study.
        Nutrients. 2020; 12: 1-12https://doi.org/10.3390/nu12113377
        • Bishop F.L.
        • Yardley L.
        • Lewith G.T.
        A systematic review of beliefs involved in the use of complementary and alternative medicine.
        J Health Psychol. 2007; 12: 851-867https://doi.org/10.1177/1359105307082447
        • Welz A.N.
        • Emberger-Klein A.
        • Menrad K.
        Why people use herbal medicine: insights from a focus-group study in Germany.
        BMC Complement Alternat Med. 2018; 18: 1-9https://doi.org/10.1186/s12906-018-2160-6
        • Embuscado M.E.
        Spices and herbs: natural sources of antioxidants – a mini review.
        J Funct Foods. 2015; 18: 811-819https://doi.org/10.1016/j.jff.2015.03.005
        • Laribi B.
        • Kouki K.
        • M’Hamdi M.
        • Bettaieb T.
        Coriander (Coriandrum sativum L.) and its bioactive constituents.
        Fitoterapia. 2015; 103: 9-26https://doi.org/10.1016/j.fitote.2015.03.012
        • Hwang J.H.
        • Cho H.J.
        • Im H bin
        • Jung Y.S.
        • Choi S.J.
        • Han D.
        Complementary and alternative medicine use among outpatients during the 2015 MERS outbreak in South Korea: a cross-sectional study.
        BMC Complement Med Therapies. 2020; 20: 147https://doi.org/10.1186/s12906-020-02945-0
        • Alami A el
        • Fattah A.
        • Chait A.
        Medicinal plants used for the prevention purposes during the COVID-19 pandemic in Morocco.
        J Anal Sci Appl Biotechnol. 2020; 2: 4-11https://doi.org/10.48402/IMIST.PRSM/jasab-v2i1.21056
        • Elmowalid G.A.
        • Abd El-Hamid M.I.
        • Abd El-Wahab A.M.
        • Atta M.
        • Abd El-Naser G.
        • Attia A.M.
        Garlic and ginger extracts modulated broiler chicks innate immune responses and enhanced multidrug resistant Escherichia coli O78 clearance.
        Comp Immunol Microbiol Infect Diseases. 2019; 66https://doi.org/10.1016/j.cimid.2019.101334
        • Wang K.
        • Conlon M.
        • Ren W.
        • Chen B.B.
        • Bączek T.
        Natural products as targeted modulators of the immune system.
        Clin Develop Immunol. 2021; 2018https://doi.org/10.1155/2018/7862782
        • Jayawardena R.
        • Byrne N.M.
        • Soares M.J.
        • Katulanda P.
        • Hills A.P.
        Body weight perception and weight loss practices among Sri Lankan adults.
        Obesity Res Clin Pract. 2014; 8https://doi.org/10.1016/J.ORCP.2013.05.003