|Year : 2023 | Volume
| Issue : 1 | Page : 99
National food and nutrition surveillance dietary supplement use among Iranian households during COVID-19 epidemic lockdown: Less access in those who may need more
Delaram Ghodsi1, Bahareh Nikooyeh1, Maryam Amini1, Samira Rabiei1, Azam Doustmohammadian2, Zahra Abdollahi3, Mina Minaie3, Farzaneh Sadeghi3, Cain C T. Clark4, Tirang R Neyestani1, Hamid Rasekhi1
1 Department of Nutrition Research, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran
2 Gastrointestinal and Liver Diseases Research Center (GILDRC), Iran University of Medical Sciences, Tehran, Iran
3 Community Nutrition Office, Deputy of Health, Iran Ministry of Health and Medical Education, Tehran, Iran
4 Centre for Intelligent Healthcare, Coventry University, Coventry, CV1 5FB, U. K
|Date of Submission||15-Jun-2022|
|Date of Acceptance||27-Oct-2022|
|Date of Web Publication||27-Jul-2023|
Department of Nutrition Research, National Nutrition and Food Technology Research Institute and Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran
Source of Support: None, Conflict of Interest: None
Background: The coronavirus disease 2019 (COVID-19) pandemic elicited the general population to use various dietary supplements (DSs) and nutraceuticals as a protective means against the disease. The present study aimed to evaluate changes and certain determinants of DS intake during the COVID-19 lockdown among Iranian households. Methods: This nationwide cross-sectional study was conducted from April 4 to April 25, 2020, during which Iran was in lockdown. To collect data, a web-based electronic self-administered questionnaire was created. The data were compared among provinces based on their food security situations. Results: A total of 21,290 households were included in the analyses. Approximately 27% of the households were using DSs after the epidemic. The most common DSs used were vitamin D (42%) and vitamin C (20%), followed by multi-vitamin (16%), zinc (9%), omega-3 (6%), vitamin A (4%), and probiotics (3%). Logistic regression analysis revealed that DS intake was directly associated with the household income but inversely with household size and the food security status of the provinces. DS intake was positively associated with the presence of high-risk persons in the households, the education of the households' head, and the presence of a person with a history of COVID-19 within the household. Conclusions: During epidemic lockdown, DS use was remarkably increased among the Iranian households. Apart from the debatable usefulness of DSs against COVID-19, the inverse association of DS use with a household's income and provincial food security well indicates inequity in accessibility to DS. Actions to improve the nutritional status of the under-privileged populations including targeted supplementation are strongly recommended.
Keywords: COVID-19, dietary supplements, public health surveillance, surveys and questionnaires
|How to cite this article:|
Ghodsi D, Nikooyeh B, Amini M, Rabiei S, Doustmohammadian A, Abdollahi Z, Minaie M, Sadeghi F, T. Clark CC, Neyestani TR, Rasekhi H. National food and nutrition surveillance dietary supplement use among Iranian households during COVID-19 epidemic lockdown: Less access in those who may need more. Int J Prev Med 2023;14:99
|How to cite this URL:|
Ghodsi D, Nikooyeh B, Amini M, Rabiei S, Doustmohammadian A, Abdollahi Z, Minaie M, Sadeghi F, T. Clark CC, Neyestani TR, Rasekhi H. National food and nutrition surveillance dietary supplement use among Iranian households during COVID-19 epidemic lockdown: Less access in those who may need more. Int J Prev Med [serial online] 2023 [cited 2023 Sep 27];14:99. Available from: https://www.ijpvmjournal.net/text.asp?2023/14/1/99/382443
| Introduction|| |
The epidemic of the novel coronavirus disease (COVID-19) was first reported in late December 2019, solely in the city of Wuhan, China. Despite strategies adopted by the Chinese government to stop the infection, it continued to spread throughout the world. By the end of January 2020, the World Health Organization (WHO) declared COVID-19 as a public health emergency of international concern, and on March 11, 2020, WHO characterized this epidemiological phenomenon as a pandemic.
The first report of the epidemic in Iran was on February 19, 2020; therefrom, the infection rapidly disseminated to all provinces of Iran within 15 days. During this time, many individuals sought additional protections, especially via the consumption of various dietary supplements (DSs) and nutraceuticals because of their reported beneficial effects. Although a patient's nutritional status does seem to play a role in COVID-19 susceptibility and outcomes,,,,, the beginning of the pandemic was accompanied by a remarkable increase in sales of vitamins and other supplements despite the lack of any evidence supporting their use against COVID-19. In the United States, for example, DS and nutraceutical sales have had the modest annual growth in recent years (approximately 5% or a $345 million increase in 2019), but during the 6-week period preceding April 5, 2020, they increased by 44% ($435 million) relative to the same period in 2019.
DSs contain one or more dietary compounds, such as vitamins, minerals, amino acids, or other substances, with a nutritional or physiological effect. A number of micro-nutrients, including vitamins C and D and zinc, have been shown to play key roles in supporting immune functions, and in reducing the risk of respiratory infection.,, A biologically plausible role exists for the use of certain DSs., Vitamin D, for instance, has been suggested to reduce severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission by enhancing anti-viral immunity and to reduce mortality, mitigating the cytokine storm linked with severe COVID-19., Zinc also supports the function of the immune system and may have specific anti-viral effects. There are many other DSs available, including omega-3 fatty acids (“fish oil”), probiotics, and plant isolates, such as garlic. The use of specific DSs in both prevention and treatment of infection with SARS-CoV-2 has been promoted since the beginning of the current coronavirus pandemic. Nevertheless, robust evidence to support a role for DSs in preventing infection with SARS-CoV-2 is not available., Considering the modest, but significant, effect of DSs against COVID-19, this study was undertaken to evaluate the changes in DS use during the COVID-19 lockdown period among the Iranian population and their possible associations with some socio-economic variables.
| Methods|| |
This was a cross-sectional descriptive-analytical study using a web-based electronic self-administered questionnaire. The protocol of this study has already been fully described elsewhere. Briefly, several virtual sessions were held to design a questionnaire that aimed to detect any changes in the dietary habits of the Iranian households including DS use following the coronavirus epidemic. The content validity of the questionnaire was assured by a panel of seven internal (involved in the compilation of the questionnaire) and three external (not involved in the compilation of the questionnaire) nutrition experts. The questionnaire was uploaded to a previously created link (https://panel.rabit.ir/s/c1NEPPXL483.html). Then, an official letter from the Community Nutrition Office, Deputy of Health, Iran Ministry of Health (MOH), was sent to the vice chancellors in health affairs and the Community Nutrition Offices of the medical universities of all provinces. In the letter, the objectives of the project and the related link to be followed by the respondents were mentioned. The provincial health and nutrition workers were also requested to notify the community under their service coverage. In addition, the link was distributed widely to Telegram and WhatsApp. This phase of the survey was conducted from April 4 to April 25, 2020, during which Iran was experiencing the coronavirus epidemic lockdown. The variables of interest were compared among provinces based on their food security status, according to the latest national report in which provinces were categorized as food insecure, semi-secure, and secure.
Each respondent was directed to complete the questionnaire on behalf of his/her household. The questionnaires were anonymous to ensure the privacy and independence of the participants. Questions were asked pertaining to socio-economic status (SES) and any DS use by the household members during the epidemic. SES section included data regarding the gender, education, and occupation of the heads of the households, households' size, province and region of the residency (urban/rural), presence of a high-risk person in the household (i.e., under-5 children, pregnant or lactating women, elderly), and any changes in the households' income. The presence of a person with a history of COVID-19 within the household was also asked.
Completion of the questionnaire was voluntary and anonymous. Furthermore, the respondents were assured about the confidentiality of information and privacy. This study was approved by the Ethics Committee of the National Nutrition and Food Technology Research Institute (IR.SBMU.NNFTRI.REC.1399.066).
The descriptive analysis was conducted to assess the distribution of SES among respondents. Logistic regressions were fitted to examine which factors contributed to the DS intake. A two-tailed P < 0.05 was, a priori, considered significant. The dependent variable in regression models was supplement intake.
The gender of the households' heads (male, female), living in urban/rural areas (urban, rural), the households' size (one to two, three to five, six and more), presence of the high-risk member(s) in the households (none, under 5 years old, pregnant/lactating, elderly, more than one member), occupation of the heads (employee, freelance, retired, health worker, teacher, driver, other), the educational status of the heads [master and higher, bachelor, associate degree, diploma, high school, theological education (preacher)], changes in the income of the household (no changes, small decrease, half, cut), infection of any member of the family with COVID-19 (no, yes), and the food security status of the provinces (secure, semi-secure, insecure) were the independent variables assessed. In all analyses, sampling weights were used to account for the complex sampling design and to allow inferences valid for the population. All analyses were performed using Stata version 16.0 (StataCorp LLC).
| Results|| |
A total of 21,290 households were included in the analyses. [Table 1] shows the socio-demographic characteristics of the studied households. The mean age of the households' heads was 44.7 [95% confidence interval (CI)=44.2–44.9] years, and the data indicated that 26.2% of the households (weighted percentage) resided in rural areas.
Approximately 27% of the households were taking DSs after the COVID-19 epidemic. The most used DSs during the COVID-19 lockdown were vitamin D (42%), vitamin C (20%), and multi-vitamin (16%), followed by zinc (9%), omega-3 (6%), vitamin A (4%), and probiotics (3%) [Figure 1].
|Figure 1: The most commonly used dietary supplements in Iranian households during the lockdown period|
Click here to view
[Table 2] represents the association between DS intake and socio-economic characteristics. The logistic regression analysis revealed that DS intake was significantly associated with the size of the households, the presence of high-risk persons in the households, the education of the households' head, changes in the households' income, presence of a person with the history of COVID-19 within the household, and food security status of the province.
|Table 2: Logistic regression models of changes in intake of supplement after COVID-19 epidemic|
Click here to view
Compared with households who had no high-risk members, the odds ratios (ORs) of DS use in households with high-risk members were significantly higher (elderly: OR = 1.45, 95% CI = 1.24–1.27; under 5-year children: OR = 1.45, 95% CI = 1.24–1.27, pregnant/lactating mother: OR = 1.1, 95% CI = 1.01–1.62). Households with COVID-19-affected member (s) had over two times increased odds of using DSs (OR = 2.1; 95% CI, 1.72–2.57, P < 0.001) as compared with the households with no infected person. A decrement of the household income was directly associated with lesser use of DSs, compared with the households with no income change during the lockdown. Similarly, DS use in the households living in food-insecure provinces was significantly lower compared with those residing in the secure provinces (OR = 0.32; 95% CI, 0.28–0.37).
| Discussion|| |
This is the first national report on DS use in Iranian households during the COVID-19 lockdown period. The mean households' size and the ratio of urban to rural households were in agreement with the information of the latest population census in Iran, suggesting that the study population was representative (~1%) of the whole country households. We have already reported the effects of COVID-19 lockdown on certain dietary habits of the Iranian households., In this piece of work, COVID-19 epidemic-induced changes of DS use were evaluated.
We found that vitamins D and C were the most common supplements used during the COVID-19 epidemic. In accord with our findings, another study reported that the intake of vitamins D and C during the COVID-19 epidemic was higher than that before the pandemic. Also, another study from Saudi Arabia found that vitamin C was used during the COVID-19 pandemic by almost all DS users. According to a survey carried out in Poland, 56% of respondents were consuming vitamin D pills. Overall, vitamin C,,, vitamin D, and omega-3 fatty acids, were among the most frequently taken DSs in the pandemic. Previous provincial studies from Iran demonstrated that iron, calcium, vitamin D, and multi-vitamin were the most commonly used DSs. Therefore, the pattern of DS use in Iran is likely to have changed because of the epidemic.
The effects of various micro-nutrients in COVID-19 have been investigated in several studies since the beginning of the pandemic.,, Nevertheless, the results have been equivocal. It has been documented that adequate circulating concentrations of 25-hydroxycalciferol (25(OH) D) and vitamin C may reduce the incidence of coronavirus-induced “cytokine storm”,, which is strongly associated with lung injury and poor prognosis of the disease.
Currently, the large-scale administration of vitamin D supplements to populations at risk of COVID-19 is widely recommended.,, However, some recommendations seem to be more of a commercial opportunity, rather than fulfilling real nutritional requirements. Indeed, a recent study reported a significant increase in the number of advertisements in favor of dietary supplementation for the recent pandemic compared with before. The UK supplement market, for instance, increased by 19.5% in the period, leading up to the national “lockdown” in early March 2020, with a 110% rise in sales of vitamin C and a 93% rise in sales of multi-vitamin supplements. Likewise, zinc supplement sales increased by 415% over the 7-day period ending March 8 at the peak of COVID-19 concern in the US. Although the pandemic continues, the urgent need for correct information about the beneficial doses of DSs is clear. Accordingly, information that is supported by rigorous trials could offset misleading claims for DSs, and in this regard, consumer education and development of related regulations are suggested.
According to the current study, DS intake was inversely related to the households' size. In other words, it seems that the size of the households may limit access to all facilities including DSs. In a recent study, households' size was reported to be a potential determinant of the COVID-19 pandemic,, and another study revealed that the COVID-19 death rate among the upper quintile of house crowding was almost 3 times as much as household crowding of the lowest quintile. This indicates that more crowded Iranian households who may need more DSs probably have less access to them.
We found a direct association between education and DS use. The relationship between education level and DS use has already been reported from Iran, and other countries, suggesting that a higher level of education may be conducive to greater knowledge about the positive effect of adequate nutrition in boosting the immune system and prevention of infection.
Our findings demonstrated a direct association between the decrement of income during lockdown and DS use. Given that dietary intakes are often influenced by income, low-income households are more likely to have lower quality and lower nutrient-rich diets. Nutrient adequacy in adults is incontrovertibly income-related,, and adults in poor socio-economic status are reported to have a higher prevalence of micro-nutrient inadequacies based on total nutrient intakes from both diet and DS. Dietary supplements, on the other hand, can contribute in nutritional adequacy, especially in low-income sub-populations. In addition, our study revealed that the food insecurity status of the provinces was inversely related with DS use in the households, again indicating that more needy households may have less access to DS. These findings well confirm the fact that household welfare and food security are strongly correlated with each other.
To the best of our knowledge, this was the first nationwide survey on changes of dietary habits, including DS use, among Iranian households. As the questionnaires were IT-based, analysis and reporting to the policy-makers could be performed at the earliest. Nevertheless, some limitations of this study are acknowledged. First, the questionnaire was self-administrated so that only people interested in the subject might have participated in the survey. Second, those people without internet access were inevitably excluded. However, these limitations are common in online surveys,,, but as they provide the possibility to gather data without the need for face-to-face interview and a high risk of viral transmission, online surveys are preferable, especially during the COVID-19 epidemic., Moreover, the conformity of our data on the mean household size and the ratio of urban to rural households with the latest report of population census in Iran indicates that the study population could be regarded as the representative of the whole country households.
| Conclusions|| |
We found that 27% of the studied population was taking DS during COVID-19 lockdown. Vitamins D and C were the mostly used supplements. DS intake was less among households with a lower income, and the food insecurity status of the provinces was inversely related to DS intake of the households, which implies the impact of prosperousness on the well-being of the populations. DS intake was explored in the context of socio-economic determinants, namely, households' size and the educational level of the households' heads. Considering the noticeable contribution of DS in nutritional adequacy and hence immuno-competence against human diseases including coronavirus infection,, early interventions to improve the nutritional status (including targeted supplementation) of the low-income households is strongly recommended.
COVID-19: Coronavirus disease of 2019
DSs: Dietary Supplements
NNFTRI: National Nutrition and Food Technology Research Institute
SES: Socio-economic status
WHO: World Health Organization.
The authors would like to extend their gratitude and acknowledgments to all study participants and to all colleagues for their support and help in disseminating the questionnaire. We would like to thank our colleagues in Community Nutrition Offices of the medical universities of all provinces.
Availability of data and materials
Data described in this manuscript will be made available upon reasonable request to the project's main supervisor
Ethics approval and consent to participate
All procedures were approved by Ethics Committee of the National Nutrition and Food Technology Research Institute (IR.SBMU. NNFTRI.REC.1399.066). All participants were properly instructed and gave online their informed consent to participate.
Financial support and sponsorship
This study received COVID-19 research grant from Shahid Beheshti University of Medical Sciences (No. 25777).
Conflicts of interest
There are no conflicts of interest.
| References|| |
Meldrum DR, Morris MA, Gambone JC. Obesity pandemic: Causes, consequences, and solutions—but do we have the will? Fertil Steril 2017;107:833-9.
Black R. Micronutrient deficiency: An underlying cause of morbidity and mortality. Bull World Health Organ. 2003;81:79.
Sohrabi C, Alsafi Z, O'Neill N, Khan M, Kerwan A, Al-Jabir A, et al
. World Health Organization declares global emergency: A review of the 2019 novel coronavirus (COVID-19). Int J Surg 2020;76:71-6.
Zabetakis I, Lordan R, Norton C, Tsoupras A. COVID-19: The inflammation link and the role of nutrition in potential mitigation. Nutrients 2020;12:1466.
James PT, Ali Z, Armitage AE, Bonell A, Cerami C, Drakesmith H, et al
. Could nutrition modulate COVID-19 susceptibility and severity of disease? A systematic review. medRxiv. 2020. https://doi.org/10.1101/20184.108.40.20614395
Silverio R, Gonçalves DC, Andrade MF, Seelaender M. Coronavirus disease 2019 (COVID-19) and nutritional status: The missing link? Adv Nutr 2021;12:682-92.
Richards TJ, Rickard B. COVID-19 impact on fruit and vegetable markets. Can J Agric Econ 2020;68:189-94.
Calder PC, Carr AC, Gombart AF, Eggersdorfer M. Optimal nutritional status for a well-functioning immune system is an important factor to protect against viral infections. Nutrients 2020;12:1181. doi: 10.3390/nu12041181.
de Faria Coelho-Ravagnani C, Corgosinho FC, Sanches FLFZ, Prado CMM, Laviano A, Mota JF. Dietary recommendations during the COVID-19 pandemic. Nutr Rev 2020;79:382-93.
Ruíz-Roso MB, de Carvalho Padilha P, Matilla-Escalante DC, Brun P, Ulloa N, Acevedo-Correa D, et al
. Changes of physical activity and ultra-processed food consumption in adolescents from different countries during Covid-19 pandemic: An observational study. Nutrients 2020;12:2289. doi: 10.3390/nu12082289.
Calder PC. Nutrition, immunity and COVID-19. BMJ Nutr Prev Health 2020;3:74.
Gombart AF, Pierre A, Maggini S. A review of micronutrients and the immune system–working in harmony to reduce the risk of infection. Nutrients 2020;12:236.
Martineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P, et al
. Vitamin D supplementation to prevent acute respiratory tract infections: Systematic review and meta-analysis of individual participant data. BMJ 2017;356:i6583. doi: 10.1136/bmj.i6583.
Louca P, Murray B, Klaser K, Graham MS, Mazidi M, Leeming ER, 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 Prev Health 2021;4:149-57.
Grant WB, Lahore H, McDonnell SL, Baggerly CA, French CB, Aliano JL, et al
. Evidence that vitamin D supplementation could reduce risk of influenza and COVID-19 infections and deaths. Nutrients 2020;12:988. doi: 10.3390/nu12040988.
Khare D, Godbole NM, Pawar SD, Mohan V, Pandey G, Gupta S, et al
. Calcitriol [1, 25 [OH] 2 D3] pre-and post-treatment suppresses inflammatory response to influenza A (H1N1) infection in human lung A549 epithelial cells. Eur J Nutr 2013;52:1405-15.
Read S, Obeid S, Ahlenstiel C, Ahlenstiel G. The role of zinc in antiviral immunity. Adv Nutr 2019;10:696-710.
Lentjes MA. The balance between food and dietary supplements in the general population. Proc Nutr Soc 2019;78:97-109.
Adams KK, Baker WL, Sobieraj DM. Myth Busters: Dietary supplements and COVID-19. Ann Pharmacother 2020;54:820-6.
Cheng VC-C, Wong S-C, Yuen K-Y. Estimating coronavirus disease 2019 infection risk in health care workers. JAMA Network Open 2020;3:e209687.
Rasekhi H, Rabiei S, Amini M, Ghodsi D, Doustmohammadian A, Nikooyeh B, et al
. COVID-19 epidemic-induced changes of dietary intake of Iran population during lockdown period: The study protocol, National Food and Nutrition Surveillance. Nutr Food Sci Res 2021;8:1-4.
Kolahdooz F, Najafi F. Report of a National Survey: Food Security Information and Mapping System in Iran [Persian]. Tehran: Iran Ministry of Health, Treatment and Medical Education; 2012.
Rabiei S, Ghodsi D, Amini M, Nikooyeh B, Rasekhi H, Doustmohammadian A, et al
. Changes in fast food intake in Iranian households during the lockdown period caused by COVID-19 virus emergency, National Food and Nutrition Surveillance. Food Sci Nutr 2022;10:39-48.
Nikooyeh B, Rabiei S, Amini M, Ghodsi D, Rasekhi H, Doustmohammadian A, et al
. COVID-19 epidemic lockdown-induced changes of cereals and animal protein foods consumption of Iran population: The first nationwide survey. J Health Popul Nutr 2022;41:1-9. doi: 10.1186/s41043-022-00310-0.
Hamulka J, Jeruszka-Bielak M, Górnicka M, Drywień ME, Zielinska-Pukos MA. Dietary supplements during COVID-19 outbreak. Results of google trends analysis supported by PLifeCOVID-19 online studies. Nutrients 2020;13. doi: 10.3390/nu13010054.
Alyami HS, Orabi MAA, Aldhabbah FM, Alturki HN, Aburas WI, Alfayez AI, et al
. Knowledge about COVID-19 and beliefs about and use of herbal products during the COVID-19 pandemic: A cross-sectional study in Saudi Arabia. Saudi Pharm J 2020;28:1326-32.
Barnes K, Ball L, Desbrow B, Alsharairi N, Ahmed F. Consumption and reasons for use of dietary supplements in an Australian university population. Nutrition 2016;32:524-30.
Cowan AE, Jun S, Gahche JJ, Tooze JA, Dwyer JT, Eicher-Miller HA, et al
. Dietary supplement use differs by socioeconomic and health-related characteristics among U.S. adults, NHANES 2011–2014. Nutrients 2018;10:1114. doi: 10.3390/nu10081114.
Dickinson A, Blatman J, El-Dash N, Franco JC. Consumer usage and reasons for using dietary supplements: Report of a series of surveys. J Am Coll Nutr 2014;33:176-82.
Maddah M, Shoyooie R, Akbarian Z, RostamNejad M, Soleymani M. Dietary supplement use among Iranian adults: A study in northern Iran. Med J Nutr Metab 2013;6:69-72.
Carr AC. A new clinical trial to test high-dose vitamin C in patients with COVID-19. Crit Care 2020;24:133.
Hemilä H, Chalker E. Vitamin C as a possible therapy for COVID-19. Infect Chemother 2020;52:222-3.
Pinheiro MM, Fabbri A, Infante M. Cytokine storm modulation in COVID-19: A proposed role for vitamin D and DPP-4 inhibitor combination therapy (VIDPP-4i). Immunotherapy 2021;13:753-65.
de Melo AF, Homem-de-Mello M. High-dose intravenous vitamin C may help in cytokine storm in severe SARS-CoV-2 infection. Crit Care 2020;24:1-2.
Hu B, Huang S, Yin L. The cytokine storm and COVID-19. J Med Virol 2021;93:250-6.
Ferder L, Martín Giménez VM, Inserra F, Tajer C, Antonietti L, Mariani J, et al
. Vitamin D supplementation as a rational pharmacological approach in the COVID-19 pandemic. Am J Physiol-Lung Cell Mol Physiol 2020;319:L941-8.
Ranaei V, Pilevar Z, Neyestani TR. Can raising vitamin D status slow down covid-19 waves? Nut Food Sci Res 2021;8:1-3.
Okuhara T, Yokota R, Shirabe R, Iye R, Okada H, Kiuchi T, et al
. Japanese newspaper advertisements for dietary supplements before and after COVID-19: A content analysis. BMJ Open 2021;11:e050898. doi: 10.1136/bmjopen-2021-050898.
Louca P, Murray B, Klaser K, Graham MS, Mazidi M, Leeming ER, et al
. Dietary supplements during the COVID-19 pandemic: Insights from 1.4 M users of the COVID Symptom Study app-a longitudinal app-based community survey. medRxiv 2020. doi: 10.1101/2020.11.27.20239087.
Liu P, McQuarrie L, Song Y, Colijn C. Modelling the impact of household size distribution on the transmission dynamics of COVID-19. J R Soc Interface 2021;18:20210036. doi: 10.1098/rsif.2021.0036.
Gillies CL, Rowlands AV, Razieh C, Nafilyan V, Chudasama Y, Islam N, et al
. Association between household size and COVID-19: A UK Biobank observational study. J R Soc Med 2022;115:138-44.
Chen JT, Krieger N. Revealing the unequal burden of COVID-19 by income, race/ethnicity, and household crowding: US county versus zip code analyses. J Public Health Manag Pract 2021;27:S43-56.
Maddah M, Sharami SH. Intake of calcium/vitamin D supplement in Iranian postmenopausal women. Arch Osteoporosis 2009;4:95-6.
French SA, Tangney CC, Crane MM, Wang Y, Appelhans BM. Nutrition quality of food purchases varies by household income: The SHoPPER study. BMC Public Health 2019;19:231.
Bailey RL, Akabas SR, Paxson EE, Thuppal SV, Saklani S, Tucker KL. Total usual intake of shortfall nutrients varies with poverty among US adults. J Nutr Educ Behav 2017;49:639-46.e3.
Monsivais P, Aggarwal A, Drewnowski A. Following federal guidelines to increase nutrient consumption may lead to higher food costs for consumers. Health Aff (Millwood) 2011;30:1471-7.
Blumberg JB, Frei B, Fulgoni VL, Weaver CM, Zeisel SH. Contribution of dietary supplements to nutritional adequacy by socioeconomic subgroups in adults of the United States. Nutrients 2017;10:4. doi: 10.3390/nu10010004.
Chegini KR, Pakravan-Charvadeh MR, Rahimian M, Gholamrezaie S. Is there a linkage between household welfare and income inequality, and food security to achieve sustainable development goals? J Cleaner Prod 2021;326:129390. doi: 10.1016/j.jclepro.2021.129390.
Litton MM, Beavers AW. The relationship between food security status and fruit and vegetable intake during the COVID-19 pandemic. Nutrients 2021;13:712. doi: 10.3390/nu13030712.
Malta DC, Szwarcwald CL, Barros MBdA, Gomes CS, Machado ÍE, Souza Júnior PRBd, et al
. The COVID-19 pandemic and changes in adult Brazilian lifestyles: A cross-sectional study, 2020. Epidemiologia e Serviços de Saúde 2020;29:e2020407. doi: 10.1590/S1679-49742020000400026.
Hargreaves JR, Morison LA, Gear JS, Kim JC, Makhubele MB, Porter JD, et al
. Assessing household wealth in health studies in developing countries: A comparison of participatory wealth ranking and survey techniques from rural South Africa. Emerg Themes Epidemiol 2007;4:1-9. doi: 10.1186/1742-7622-4-4.
Kahlon MK, Aksan N, Aubrey R, Clark N, Cowley-Morillo M, Jacobs EA, et al
. Effect of layperson-delivered, empathy-focused program of telephone calls on loneliness, depression, and anxiety among adults during the COVID-19 pandemic: A randomized clinical trial. JAMA Psychiatry 2021;78:616-22.
Alexander J, Tinkov A, Strand TA, Alehagen U, Skalny A, Aaseth J. Early nutritional interventions with zinc, selenium and vitamin D for raising anti-viral resistance against progressive COVID-19. Nutrients 2020;12:2358. doi: 10.3390/nu12082358.
Stipp MM. SARS-CoV-2: Micronutrient optimization in supporting host immunocompetence. Int J Clin Case Rep Rev 2020;2:01-10.
[Table 1], [Table 2]