COVID-19 Pandemic and Consumption of Dietary Supplements among Adult Residents of Lithuania

In the light of the changing pattern of the consumption of dietary supplements among adults in other countries during the COVID-19 pandemic, we aim to assess the prevalence of the consumption of dietary supplements with respect to the purpose of consumption and sociodemographic factors among adults in Lithuania. This study included two samples of adults from Lithuania: 870 in 2019 and 1600 in 2021. Anonymous original questionnaires were used to collect the data about the consumption of dietary supplements before and during the pandemic. The consumption of dietary supplements was prevalent among 67.2% and 78.1% of the samples, respectively. Although the majority (73.7%) of the respondents indicated that the pandemic had no effect on their use of dietary supplements, every fourth respondent’s (24.6%) consumption increased. In 2021, the consumption was more prevalent among females, respondents with university education, urban citizens, employed respondents, respondents without children, with higher income, and those who knew a person with COVID-19 (p < 0.05). During the pandemic, the strengthening of the immune system and the body were the leading reasons for consumption (49.0% and 43.5%, respectively). The consumption of dietary supplements appropriate for these purposes increased among 63.3% and 66.9% of respondents, respectively. To conclude, the consumption of dietary supplements among adults in Lithuania increased during the COVID-19 pandemic.


Introduction
Studies show that the nutritional habits of a large part of adult population are not favorable for health [1,2]. As recommended by WHO and national health care institutions, each day people should obtain a wide variety of nutrients [3,4]. According to the European Food Safety Authority, dietary supplements are intended to correct nutritional deficiencies, maintain an adequate intake of certain nutrients, or support specific physiological functions [5].
According to the results of other surveys, the COVID-19 pandemic had negative and positive effects on the nutrition and lifestyle of the majority of adults. A reduction in physical activity and an increase in the consumption of alcohol, snacks and sweets, but also fruits, vegetables, nuts, legumes, and fish or shellfish were reported [6][7][8][9]. During the pandemic, an increase in the frequency of searching for information on improving the immune system by food products or dietary supplements was observed [10,11]. Dietary supplements became the field of interest of scientists as well. The possible use of dietary supplements as a likely measure to stop the spread of SARS-CoV-2 (2019-nCoV) was analyzed. The immune-boosting, antiviral, antioxidant, or anti-inflammatory effects of dietary supplements were emphasized [12]. During the pandemic, sales of dietary supplements dramatically rose despite the depressed economic conditions [13]. A study conducted in Poland showed that the consumption of dietary supplements containing zinc and vitamin D increased during the pandemic, especially among people with higher education, or those with medical and paramedical education. With respect to the nonrestrictive registration procedures of dietary supplements, the authors emphasized the necessity of educating consumers in terms of the selection of appropriate preparations, proper nutrition, and balanced supplementation [6]. However, there is a lack of representative studies about the prevalence of consumption of various dietary supplements in various sociodemographic groups in different countries. Taking into account that there are no studies about the prevalence of consumption of dietary supplements during the pandemic in Lithuania, the aim of our study is to assess the prevalence of the consumption of dietary supplements focusing on the purpose of the consumption among social and demographic groups in Lithuania during the COVID-19 pandemic in comparison with the pre-pandemic period.

Procedure of Data Collection
The main data for this study were collected during the COVID-19 pandemic, in October and November of 2021. A representative sample of 1600 adults aged from 18 to 64 years was gathered. Male and female residents of Lithuania were included. A multistage stratified probabilistic sampling method was used to select the participants for this study from the registry of the residents of Lithuania. It ensured an equal probability for every household in the country to be surveyed and, according to the target criteria, the sample represented the general population. Data were collected by conducting computer-assisted web interviews (CAWIs). Every selected resident received an invitation to participate in this study with a link to the anonymous questionnaire by email. The participants of this study filled in the questionnaire by themselves at a time convenient to them. It was possible to fill the questionnaire only once.
For the purpose of comparison with the pre-pandemic period, an additional data sample of 905 adults aged from 18 to 64 years was included. It included data collected in March 2019. The selection of the participants was analogous to the one used in 2021. However, 60% of the respondents were interviewed by means of computer-assisted personal interviews (CAPIs) and 40% of the respondents were interviewed by means of CAWIs. CAPIs were performed by a professional interviewer using a questionnaire prepared in advance. After the exclusion of 35 (3.9%) respondents who were unable to answer the question on whether they had consumed dietary supplements within the past 12 months, we concluded with a sample of 870 respondents whose answers were used for statistical analysis.
In cases of refusal to participate in the study by invited individuals, additional participants were randomly selected and invited from a group of people of the same age, sex, and geographical characteristics.
The distribution of the respondents in both samples by social and demographic factors is presented in Table 1.

Description of the Questionnaire
Two anonymous validated original questionnaires were used for this study: one in 2019 and the other in 2021. We used a part of the first questionnaire. It included one question about the consumption of dietary supplements, "What dietary supplements and what for have you taken over the last 12 months?", with the answer options, "For strengthening the immune system/For disease prevention and the overall strengthening of the body/For energy boosting/For eye care/For boosting memory/For boosting the nervous system/For strengthening the cardiovascular system/For strengthening the joints, bones/For better digestion/For sleep regulation/For athletes/For weight regulation/I have not taken any dietary supplements within the last 12 months/I cannot answer". In addition, 5 questions about social and demographic characteristics were included. This study was reviewed by the Vilnius Regional Ethics Committee for Biomedical Research. The participants provided their consent by filling out the anonymous questionnaires.
In 2021, the questionnaire included questions about the social and demographic characteristics of the respondents, COVID-19 experience, subjective assessment of personal health, nutrition, consumption of dietary supplements, and physical activity. The question-naire was constructed on the basis of the questionnaire used previously in 2019 [14], by adding additional questions related to the COVID-19 pandemic and its possible impact on nutrition, consumption of dietary supplements, and physical activity. In this paper, we present the analysis of part of the questions included in the questionnaire (Table 2). Consumption of dietary supplements increased during the pandemic (I haven't consumed them before, but I've started to consume them/I consumed them before, but my consumption increased)/Consumption of dietary supplements decreased or did not change during the pandemic (I consumed them before, but my consumption decreased/They had no effect) The questionnaire also included a group of questions about social and demographic factors. Two of those questions regarding the respondents' age and place of residence were open-ended. To achieve an unambiguous interpretation of the results, we transformed them into a binary format. Respondents were asked to identify the municipality they live in. Respondents from 5 municipalities with the largest number of residents were assigned to the "City" group, while all the rest respondents were attributed to the "Towns and villages" group. The age was categorized by a median to the range up to 41-year-olds and from 42-year-olds. All other questions were close-ended. Respondents with primary or secondary education and those who finished a high school were assigned to the "Nonuniversity education" group. Respondents with unfinished or finished university studies were assigned to the "University education" group. In terms of the employment status, the "Employed" and "Unemployed" groups were created. Heads of companies or the departments, office workers, civil servants, service sector employees, sellers, workers, and farmers were assigned to the "Employed" group. Retirees, housewives, persons on parental leave, non-employed persons, and students were categorized as "Unemployed". In addition to this, more binary variables were created, such as marital status, with children up to 18 years old, and the income of a family per member. The categorization of the rest of the questionnaire is presented in Table 2.

Statistical Analysis
In order to determine the change in the consumption of different dietary supplements during the pandemic, the respondents were asked to indicate which of the dietary supplements they were made to consume more under the impact of the COVID-19 pandemic. A list of 20 dietary supplements was provided ( Table 2). During the statistical analysis, every dietary supplement from this list was assigned to one or more categories with an emphasis on the purpose of the consumption of those dietary supplements. The consumption of at least one dietary supplement in a category was defined as an increase in the consumption of dietary supplements for a specific purpose during the pandemic (Table 3). This method served us as a tool for the unambiguous comparison of consumers' expectations of the consumption of dietary supplements and the human body parts affected by the consumption of exact dietary supplements. Value "Yes" marks if a dietary supplement was assigned to the corresponding consumption purpose.
The normality of distribution of variables was tested using the Shapiro-Wilk test. With respect to the results of this test, medians with interquartile range (Q1-Q3) were presented for variables with non-normal distribution, and averages with standard distributions were presented for variables with normal distribution. Pearson's chi-squared test (χ2) was used to determine whether there was a statistically significant difference between the expected frequencies and the observed frequencies in one or more categories. Differences were considered statistically significant when the p-value was lower than 0.05.

Characteristics of the Samples
In 2021, the median age of the respondents was 42 (29-54) years. The majority of the respondents were employed, married (or had partners), from small towns or villages, people with university education, without children up to 18 years old. In 2019, the median age of the respondents was 42 (30-52) years. This sample included relatively more employed, single, and individuals with university education (p < 0.05). In both samples, the distribution of the respondents was similar according to sex, age, and place of residence (p > 0.05) ( Table 1).

The Prevalence of the Consumption of Dietary Supplements in Both Samples
In 2019, the consumption of dietary supplements was prevalent among 66.1% of the respondents.
As presented in Figure 1, the consumption of dietary supplements significantly increased among males, married, and unemployed persons (p < 0.05).

Consumption of Dietary Supplements during the COVID-19 Pandemic
In 2021, vitamin C, vitamin D, omega-3 fatty acids, magnesium, and dietary supplements for the general strengthening of the body were among the most frequently used dietary supplements highlighted in response to the question which of the dietary supplements were they made to consume more under the impact of the COVID-19 pandemic (Table 4).

Consumption of Dietary Supplements during the COVID-19 Pandemic
In 2021, vitamin C, vitamin D, omega-3 fatty acids, magnesium, and dietary supplements for the general strengthening of the body were among the most frequently used dietary supplements highlighted in response to the question which of the dietary supple-ments were they made to consume more under the impact of the COVID-19 pandemic (Table 4). During the pandemic, the consumption of dietary supplements was more prevalent among females, people with university education, respondents from cities, employed respondents, those without children, and with higher income. Additionally, those who suffered from COVID-19 or it occurred to the respondents' family members or friends consumed dietary supplements more frequently. The distribution of the respondents by their answers to the question if they consumed dietary supplements was similar in different groups of age, COVID-19 cases in respondents' families, and the degree of the severeness of COVID-19 (p > 0.05) ( Table 5).
Almost a quarter (26.1%) of the respondents indicated that the COVID-19 pandemic aroused their interest in dietary supplements. An increased interest was prevalent among a larger part of older respondents and those who had suffered from COVID-19 or their family members did. Other factors such as sex, education, place of residence, marital status, employment, income, having children, and the degree of the severeness of COVID-19 were not associated with an increase in the interest in supplements because of the pandemic (Table 5).
Suffering from COVID-19 disease personally or by family members or friends was associated with an increase in the consumption of dietary supplements during the pandemic. Other factors such as sex, age, education, place of residence, marital status, children in the family, employment, income, or COVID-19 severeness were not associated with an increase in the consumption of dietary supplements during the pandemic (Table 5). The p-values mark the probability of an association between the social and demographic variables (including COVID-19 experiences) with the consumption of dietary supplements and changes in interests and their consumption. The first two pairs of columns represent the whole sample collected in 2021, excluding missing data (n = 1586); the last pair of columns represent the adults who consumed dietary supplements in the sample collected in 2021, excluding missing data (n = 1240).

The Consumption of Dietary Supplements within the Past 12 Months and Increase in the Consumption during the Pandemic by Social and Demographic Groups
As presented in Table 6, in comparison with the 2019 data, a significant increase in the consumption of dietary supplements for strengthening the immune system, the cardiovascular system, the joints, and bones was observed during the pandemic (p < 0.05). Additionally, the analysis of data revealed a significant decrease in the consumption of dietary supplements for boosting energy, memory, eye care, regulation of sleep, and athletics (p < 0.05). Table 6. Distribution of the respondents who consumed dietary supplements by the purpose of the consumption of dietary supplements and the consumption within past 12 months (in 2019 and 2021) and an increase in the consumption during the pandemic. In 2021, the largest part of the respondents indicated that they were consuming dietary supplements within the past 12 months in order to strengthen their immune system, also in order to generally strengthen their bodies. Similarly, after the analysis of the consumption of the exact dietary supplements, these purposes were also the most prevalent. On the other hand, the differences were found in the prevalence of the consumption of dietary supplements mainly impacting other systems of the human body. In most cases, the difference was favorable; however, in the case of consumption of dietary supplements to improve digestion, it was six times lower (Table 6).

The Purpose of Consumption of Dietary Supplements
During the pandemic, the consumption of all the mentioned dietary supplements within the past 12 months was similar among males and females, except the consumption of dietary supplements for vision. The consumption of such dietary supplements was indicated by 64 (10.8%) males and 99 (15.3%) females (p = 0.021). However, the analysis of the indicated increase in the consumption of the exact dietary supplements was similar among males and females for all the mentioned purposes (p > 0.05) ( Table 6).
In 2021, younger respondents more frequently consumed dietary supplements for strengthening the immune system, boosting energy, the nervous system, for regulation of sleep, and also for athletics (respectively, 53.2% vs. 45.4%, 18.2% vs. 9.9%, 27.2% vs. 20%, 12.2% vs. 7.6%; p < 0.05). Older respondents more frequently consumed dietary supplements for strengthening their cardiovascular system, and also for joints and bones (respectively, 15.8% vs. 36.7% and 18.8% vs. 30.7%; p < 0.05). The consumption of dietary supplements for the general strengthening of the body, vision, memory, digestion, and COVID-19 prevention was similar among both age groups (p > 0.05). An increase in the consumption of dietary supplements was more common among younger respondents in the case of dietary supplements for strengthening the immune system and the general strengthening of the body (respectively, 58.9% vs. 67.2% and 62.3% vs. 71%; p < 0.05). An increase in dietary supplements for the cardiovascular system and also for joints and bones was more frequently observed among older respondents (respectively, 31.5% vs. 38.2% and 44.8% vs. 50.7%; p < 0.05). An increase in the consumption of dietary supplements appropriate for boosting energy, vision, memory increase, nervous system, digestion, regulation of sleep, and athletics was similar among both, younger, and older respondents (p > 0.05) ( Table 6).
During the pandemic, the consumption of dietary supplements for the nervous system and for the regulation of sleep was more frequent among the respondents with nonuniversity education (respectively, 28% vs. 21.5% and 14% vs. 8.1%; p < 0.05). The consumption of dietary supplements for other purposes was similar among the respondents in the higher and lower education groups (p > 0.05). An increase in the consumption of dietary supplements appropriate for boosting energy, vision, memory, and athletics was also more pronounced among the respondents with non-university education (respectively, 26.9% vs. 20.4%, 25.4% vs. 19.7%, 34.3% vs. 27.8% and 26.9% vs. 20.4%; p < 0.05). An increase in the exact dietary supplements for other purposes was not associated with education (p > 0.05).
In 2021, respondents from small towns or villages more frequently indicated the consumption of dietary supplements for improving digestion (13.1% vs. 18.8%; p = 0.007). Respondents from cities more frequently consumed dietary supplements for athletics (7.8% vs. 3.8%, p = 0.002). The consumption of dietary supplements for other purposes was similar among residents from cities and towns or villages (p > 0.05). An increase in the consumption of the exact dietary supplements for all mentioned purposes was similar among residents from cities and towns or villages (p > 0.05) ( Table 6).
During the pandemic, the consumption of dietary supplements for boosting energy, the nervous system, and athletics was more frequent among single (unmarried and living without a partner) respondents (respectively, 18.1% vs. 12.7%, 28.9% vs. 22.1% and 8.8% vs. 4.9%; p < 0.05). The consumption of dietary supplements for the cardiovascular system was more prevalent among married respondents (20.7% vs. 28.4%; p = 0.011). The consumption of dietary supplements for other purposes was not related to the marital status (p > 0.05). Additionally, an increase in the consumption of the exact dietary supplements for all the mentioned purposes was similar among married and single respondents (p > 0.05) ( Table 6).
During the pandemic, the consumption of dietary supplements for strengthening the immune system was more prevalent among respondents with children under 18 years old (46.8% vs. 52.9%; p = 0.04). The consumption of dietary supplements for strengthening the cardiovascular system and bones and joints was more prevalent among the respondents with no children under 18 years old (respectively, 30.7% vs. 20.6% and 28.2% vs. 19.5%; p < 0.05). The consumption of dietary supplements for all other purposes was not associated with having children under 18 years old (p > 0.05). An increase in the consumption of dietary supplements appropriate for boosting memory was more frequent among the respondents with children under 18 years old (32.4% vs. 26.9%; p = 0.042); the consumption of the exact dietary supplements for all other purposes was not associated with having children under 18 years old (p > 0.05) ( Table 6).
In 2021, unemployed respondents more frequently indicated the consumption of dietary supplements for boosting memory, digestion, and COVID-19 prevention (respectively, 9.7% vs. 16.7%, 15.5% vs. 21.1% and 4.6% vs. 7.9%; p < 0.05). The consumption of dietary supplements for all other purposes within the past 12 months was not associated with employment (p > 0.05). An increase in the consumption of dietary supplements appropriate for boosting energy, vision, the cardiovascular system, and COVID-19 prevention was also more frequently indicated by unemployed respondents (respectively, 20.9% vs. 27.8%, 19.9% vs. 27.3%, 33.8% vs. 41.9% and 20.9% vs. 27.8%; p < 0.05). An increase in the consumption of the exact dietary supplements for all other purposes during the pandemic was not associated with employment (p > 0.05) ( Table 6).
During the pandemic, the consumption of dietary supplements for boosting memory and the nervous system was more frequently indicated by the respondents with lower income (respectively, 13.3% vs. 9% and 29.5% vs. 20.9%; p < 0.05). The consumption of dietary supplements for the cardiovascular system and digestion was more frequently indicated by the respondents with higher income (respectively, 23.1% vs. 29.9% and 12.1% vs. 17.9%; p < 0.05). The consumption of dietary supplements for other purposes was not associated with income (p > 0.05). Additionally, an increase in the consumption of the exact dietary supplements for all purposes during the pandemic was similar among respondents with lower and higher income (p > 0.05) ( Table 6).
The consumption of dietary supplements for all purposes was similar regardless of the occurrence of COVID-19 among friends or relatives (p > 0.05). An increase in the consumption of dietary supplements appropriate for joints and bones was more frequently indicated among respondents who had suffered from COVID-19 personally or it was suffered by the respondent's family members or friends (34.7% vs. 49.3%, p = 0.003). An increase in the consumption of the exact dietary supplements for all other purposes was not associated with personal suffering from COVID-19 or undergone by their family members or friends (p > 0.05) ( Table 6).
The respondents who had suffered from COVID-19 or faced it in their families, more frequently indicated the consumption of dietary supplements for energy increase, as well as for COVID-19 prevention (respectively, 11.8% vs. 16.7% and 3.5% vs. 7.4%; p < 0.05). The consumption of dietary supplements for all other purposes was not associated with suffering from COVID-19 (p > 0.05). The respondents, who had COVID-19 personally or it occurred among their family members, more frequently indicated an increase in the consumption of dietary supplements appropriate for strengthening the immune system, general strengthening of the body, and joints and bones (respectively, 61.1% vs. 66.7%, 64.5% vs. 70.5% and 44.9% vs. 52.5%; p < 0.05). An increase in the consumption of dietary supplements appropriate for other purposes was not associated with suffering from COVID-19 by the respondents or their family members (p > 0.05) ( Table 6).
The consumption of dietary supplements and an increase in the consumption of dietary supplements for all purposes was similar regardless the degree of the severeness of COVID-19 (p > 0.05) ( Table 6).

Discussion
This study provided representative information about the consumption of dietary supplements among adult residents of Lithuania. The results of this study reveal that the consumption of dietary supplements was prevalent among the majority of the sample. Although the majority of the respondents indicated that the pandemic had had no effect on their use of dietary supplements, every fourth respondent's consumption increased. Despite the differences observed in the consumption of dietary supplements among social and demographic groups, an increase in the consumption of dietary supplements during the pandemic was driven by the COVID-19 cases among the respondents or their family members or friends. Additionally, this study shows that most of the residents selected dietary supplements with an intention to strengthen the immune system or for the general strengthening of the body. An increase in the consumption of the exact dietary supplements appropriate for the general strengthening of the body and boosting the immune system was approximately twice more prevalent than consumption of dietary supplements affecting other parts of the human body. Additionally, a significant part of the sample indicated that they use dietary supplements with an intention to improve digestion. However, the prevalence of the increased consumption of the relevant dietary supplements during the pandemic was very low.
Surprisingly, this study revealed diverging results regarding the consumption of dietary supplements in 2019 when compared to the study conducted by other authors in Lithuania and included 2573 residents of Lithuania aged from 19 to 64 years. It revealed that the consumption of dietary supplements was prevalent among approximately 82% of adults. On the other hand, we could not unambiguously compare our results to the results of this study because of the different methods of data collection and analysis [15]. Our sample collected in 2019 revealed an increase in the consumption of dietary supplements.
Additionally, according to the results of the statistical analysis of the data collected in 2021, every fourth respondent indicated that his or her consumption of dietary supplements increased during the pandemic. In addition, the consumption of dietary supplements increased among the respondents who had suffered from COVID-19 or their families or friends had suffered from this disease, as well as among those with a severe form of COVID-19. A study conducted in 2017 confirms that the prevalence of consumption of dietary supplements among adult residents of Lithuania significantly increased during the pandemic [16]. In 2017, only about half of adults (59.4%) used dietary supplements. The prevalence of the consumption was more often among females (67.7% vs. 50.2%), residents with higher education (64.9% vs. 48.8%), and persons with higher income. What is more, the most frequent reasons for consumption were strengthening of the immune system and disease prophylaxis (25.5% and 19.0%, respectively) [16]. With respect to gender and the degree of education, the results obtained are similar to the results of our study and in line with the study conducted in 2019. Interestingly, the results of our study did not reveal any difference in the prevalence of the consumption of dietary supplements with respect to the age groups. Previous studies conducted in Lithuania showed age to be an important factor for consumption of dietary supplements: the study conducted in 2019 revealed a higher prevalence of the consumption of dietary supplements among younger adults, the study of 2017 showed a higher prevalence among older adults [15,16]. Additionally, similar to our results, the study conducted in 2019 revealed that the consumption of dietary supplements was more prevalent among urban residents [15].
Studies conducted in other countries also showed similar results regarding an increase in the consumption of dietary supplements [6,17,18]. Additionally, the results show that, in all three countries, the consumption of dietary supplements for strengthening the immune system had increased [6,17,18]. Similarly, the study that was carried out in Spain and included more than a thousand adults revealed that the most frequently used supplements were combinations of multivitamins, minerals, and trace elements (27%), followed by vitamin D (25.8%) and vitamin C (22.2%) in variable doses [19]. These similarities and differences in the consumption of dietary supplements might be beneficial for the assessment of the knowledge gaps about various dietary supplements, and about behavioral differences related with cultural, regulatory, and other aspects.
A survey conducted in China in March 2020 also revealed that several dietary behaviors used to cope with COVID-19, including that an increased consumption of vitamin C, probiotics and other dietary supplements was associated with higher Household Dietary Diversity Scores. These scores were higher among older and urban residents, and among those with higher income. Gender, education level, family size, pregnancy, and having children under 5 years old in the household were not associated with the Household Dietary Diversity Score differences [18]. Surprisingly, our results show that the prevalence of consumption of dietary supplements was higher among respondents without children.
According to the studies on nutritional habits of adult residents of Lithuania, it is obvious that the majority of the adult population do not meet the nutritional recommendations [3,4], thus they are likely to face nutritional deficiencies [2,15]. The study conducted in 2019 [15] revealed that the daily consumption of cereal products and vegetables and fruits accounts for 49.5% and 57.1% of Lithuanian adult population, respectively. This leads to deficiencies of vitamins and minerals if no dietary supplements are taken. Our study provides valuable information about the prevalence of consumption of dietary supplements in the various social and demographic groups that could be used for targeted interventions in order to correct nutritional deficiencies and maintain an adequate intake of certain nutrients. According to the review performed by Harrison G.G. and published in 2010, targeted supplementation programs, enforced with other measures, may hold a great potential for a long-term progress regarding nutritional improvement, including micronutrient malnutrition. Specific targeted risk group programs were said to be crucial to both the individual and the population health in terms of food fortification. On the other hand, this applies to dietary supplementation as well. However, it was emphasized that it is important to take into account other constraining factors in order to ensure the success of targeted interventions. Despite the fact that there is some evidence that targeted educational approaches can work well, it is important to take into account factors such as unemployment and low income that cause significant barriers [20][21][22]. Our results showed similar tendencies.
Despite the fact that consumption of dietary supplements increased during the pandemic, a study, conducted in Poland revealed that the prevalence of consumption differed between the waves and, what is important, the prevalence in the third wave was not greater than in the first. During the third wave, the prevalence of the consumption of dietary supplements was likely to decrease, which indicates the necessity of additional studies on this topic in the near future [6].

Limitations
A longitudinal study would have possibly provided more accurate results. On the other hand, this study included a representative sample larger than sufficient according to sex, age, place of residence, and education to reveal the consumption of dietary supplements among adult residents of Lithuania. Due to the data availability, we were not able to assess the representativeness according to other social and demographic factors.
Additionally, in order to assess the increase in the consumption of dietary supplements driven by specific purposes, we categorized dietary supplements with respect to the most impacted parts of the human body, despite the fact that dietary supplements are likely to have a much wider effect.
In addition, we did not collect the data about the time of consumption of dietary supplements with respect to the COVID-19 cases among the respondents or their families, friends.
Additionally, we analyzed only a limited number of possible factors that might have influenced the consumption of dietary supplements. In future studies, it would be beneficial to investigate this issue with more possible factors that might be related with the changes in the consumption of dietary supplements.
In order to assess the exact deficiencies in nutrients and the actual needs for the consumption of dietary supplements, it would be beneficial to investigate the actual nutrition taking into account the consumption of dietary supplements.

Conclusions
The consumption of dietary supplements was prevalent among the majority of adults in Lithuania and it increased during the COVID-19 pandemic. The consumption was more prevalent among females, respondents with university education, urban citizens, employed respondents, respondents without children, with higher income, and those who knew a person with COVID-19 infection. Most of the adults selected dietary supplements with an intention to strengthen the immune system or for the general strengthening of the body.  Institutional Review Board Statement: This study was reviewed by the Vilnius Regional Ethics Committee for Biomedical Research. The authors received a confirmation that the study did not require approval of the Committee.

Informed Consent Statement:
The participants were informed about the aim of the study and the data processing in Vilnius University. They provided their consent by voluntarily filling out the anonymous questionnaire. With respect to the fact that we collected anonymous non-sensitive data and that the sample was large, signing an additional informed consent would have unreasonably increased the costs of the data collection.