Consumers’ perceptions of dietary supplements before and after the COVID-19 pandemic based on big data

Coronavirus disease 2019 (COVID-19) has had a huge impact on human health and society as a whole worldwide. Each country has established quarantine policies and guidelines such as lockdowns, social distancing, restrictions on private gatherings, and strict regulations [1]. While these changes have increased negative life patterns related to health, including reduced physical activity and increased intake of unhealthy foods, they have also increased the awareness of the importance of health and dietary supplements (DSs) for the prevention and recovery from the coronavirus, as well as interest in health maintenance [2, 3]. During the COVID-19 pandemic, many people tried to maintain their health by consuming various DSs and functional foods that were expected to have beneficial effects [3]. Sales of DSs, including vitamins, soared as the pandemic grew in several countries, including Korea, the United States, the United Kingdom, and Poland [4, 5, 6, 7]. In South Korea, sales of omega-3, vitamin D, krill oil, probiotics, and multivitamins have increased after the COVID-19 pandemic [8]. In addition, sales of red ginseng, known to help strengthen immunity, increased by 92.3% and those of probiotic-related products by 111.5% [9]. This increase was driven by consumer awareness that DSs and functional foods can protect against or mitigate the effects of infections due to the various “immunity-enhancing” claims of these products [5, 10]. Indeed, several studies have demonstrated the effectiveness of these nutritional interventions as immune stimulants and protection against viral infections [11]. Vitamin D was associated with lower intubation rates and shorter hospital stays [12], and a large-scale survey of app-based communities in the United Kingdom, United States, and Sweden reported that individuals consuming probiotics, omega-3 fatty acids, multivitamins, and vitamin D had 14%, 12%, and 13% lower risks of contracting COVID-19, respectively [6].

The US Food and Drug Administration (FDA) [13] defines DSs as products that contain specific “dietary ingredients” such as vitamins, herbs, and minerals to “supplement the diet”. Accordingly, consumers commonly use DSs not only to strengthen the immune system but also to recover from fatigue, supplement nutrition, and assist in weight gain and loss [14, 15]. However, the reasons for consuming DSs are often complex, combining social, psychological, knowledge, and economic factors [16]. Supplement use reportedly increases with age, income, and education, and women are more likely to use supplements than men [17]. In addition, people using DSs are characterized by health-related habits, including better dietary patterns, higher physical activity, maintenance of normal body weight, and tobacco avoidance [17].

Recent consumer-related studies on DSs have mainly focused on DS users and their sociodemographic profiles [17, 18], reasons for use [19, 20], social-cognitive and psychological factors [21], health awareness and familiarity [22, 23], and usage patterns [24]. In addition, studies on the knowledge and attitude regarding DSs among general consumers are being conducted [25, 26, 27]. However, consumers’ perceptions of DS are believed to have changed amidst individual life, social, and environmental changes since the COVID-19 pandemic. Although consumer studies have been conducted, including those evaluating DS use [2, 15] and DS-related behaviors and beliefs [25], they remain insufficient. In particular, few studies have reported on the changes in the perceptions of DS before and after the COVID-19 pandemic. The COVID-19 pandemic and the resulting changes in social trends have drastically altered consumer perceptions and consumption of DS, and we believe that studying their changed perceptions will provide important clues to understanding consumer behavior.

Owing to the recent development of information and communication technology, the use of smartphones has become commonplace, and social media is actively used, creating a vast amount of data [28]. Big data refers to data on an enormous scale, and generally refers to data that are difficult to process with general software technology owing to the large amount of standardized or unstructured data [29]. A technology to analyze very large data has recently been developed, which has enabled data analysis and created new values. Through big data, it is possible to guess the thoughts of a large number of people by using the keywords of articles distributed online or on SNS or the analysis results of search keywords [30]. Big data has also been used in DS-related studies: Kamiński et al. [31] analyzed the popularity of DSs using Google search rankings, while Hamulka et al. [32] investigated the DS phenomenon during the COVID-19 pandemic using Google Trends analysis. Although big data are used in many research fields as an effective tool to capture meaningful trends and perceptions of the public, it is lacking in DS consumer-related fields. Moreover, big data is considered the best tool for examining consumer perceptions and changes in trends related to DSs before and after the COVID-19 pandemic. Big data analysis, which reflects consumers' opinions in their daily lives, is highly valuable for uncovering new insights and valuable implications that may not be revealed in existing studies utilizing interview or survey techniques [30]. Furthermore, given its ability to rapidly and accurately collect vast amounts of data accumulated from daily life and objectively analyze consumer opinions, we believe that big data on changes in perceptions of DS can provide crucial inspiration for DS consumer research.

This empirical study assessed DS consumer behavior before and after the pandemic as the demand for DSs increases in daily diets. This study aimed to explore consumers’ perceptions and trends around DSs before and after the COVID-19 pandemic through the analysis of big data using social networks.

This study identified words closely related to the keyword “dietary supplement” based on the analysis of big data from social media and investigated consumers’ perceptions and trend changes in DS before and after the COVID-19 pandemic. The main findings of this study are as follows: in 2019, 37,313 DS-related keywords appeared in social media, compared to 35,336 in 2021. The keywords DS-related that frequently appeared in 2019 and 2021 were “recommend”, “vitamin”, “health”, “children”, “feed”, and “multiple”, which indicated the main perceptions that Korean consumers have about DS. These findings suggest people in Korea are generally interested in children's DSs, multiple DSs, vitamins, and Lactobacillus and also want to obtain recommendations for DS through social media. In addition, the high TF-IDF values for “calcium”, “lutein”, “skin”, and “immunity” also reveal the main perceptions related to DS. In this study, immunity improvement can be interpreted as a strong expectation of Korean consumers for DS before and after the COVID-19 pandemic. Global studies after the COVID-19 pandemic also reported similar trends [34]. In addition, “lutein” reflects an increased interest in eye health owing to the recent surge in smartphone use. In particular, as the prevalence of myopia increases worldwide due to decreased outdoor time and increased screen time after the COVID-19 pandemic, interest in and demand for lutein are also expected to increase [35]. According to the Korea Health Supplements Association, the lutein DS market grew by 67.8% in 2020 compared to 2019 [36]. Meanwhile, the big data results also reflected social phenomena related to DSs. Among the low TD-IDF values after the COVID-19 pandemic, “baby” and “pregnant woman” stand out. This is attributable to the decreased marriage and birth rates after the pandemic and situations in which marriage and childbirth were postponed due to anxiety caused by the virus, as well as the effects of economic recessions not only in Korea but also in other countries [37]. One of the keywords with greatly increased TD-IDF values after the COVID-19 pandemic was “joint”. A study that investigated changes in menopausal symptoms during the COVID-19 pandemic among middle-aged Korean women [38] reported that the participants had more severe symptoms than before the pandemic, especially bone and joint pain. A study in Japan that analyzed the contents of newspaper advertisements about DSs before and after the COVID-19 pandemic [39] reported significantly higher joint improvement-related content after the pandemic compared to before, and the difference was highest in ranking. The authors of both studies speculated that these observations had occurred due to decreased physical activity because of restrictions on going out due to the risk of COVID-19 infection. Another notable DS-related search term was “feed”. The pet industry in Korea has grown rapidly, with 30% of the population raising companion animals. In addition, the industry has grown by 78% in 6 years, from 1.9 trillion won in 2015 to 3.4 trillion won in 2021 and is expected to reach 6 trillion won in 2027 [40]. In the case of overseas direct purchase shopping malls for domestic DSs, sales of DSs for companion animals have increased by more than 67% in the 2 years since 2019 [41]. Various product groups related to joint and bone health, oral, intestinal, eye, and skin health, including omega-3, are gaining popularity as DSs for companion animals [42].

The result of the semantic network analysis connecting demand/purpose with DS as keywords in 2019 showed a network centered on “vitamin” and “health management”. This can be interpreted to mean that consumers who searched for DSs were mainly seeking vitamins, with high demands for DSs for healthcare. In contrast, in 2021, the values were highest for deficiency and need, in which the purpose of searching for DSs was a lack of nutrient intake and awareness of the need. In addition, before the COVID-19 pandemic, DS and vitamins were recognized as a need or purpose for health care in the life cycle, such as pregnancy. However, after the pandemic, the perception has changed to disease prevention and treatment. Mohsen et al. [3] reported that the pandemic significantly changed participants' attitudes toward DSs, perceiving that DSs supported health and strengthened immunity due to the belief that these nutrients are immune-boosting and have antiviral, antioxidant, and anti-inflammatory effects [11]. Because of these consumer perceptions, DS usage has increased since the COVID-19 pandemic and Korea’s DS and health functional food market increased from 4.7 trillion won in 2019 to 5 trillion won in 2021. In the case of iHerb, a global health shopping mall specializing in DS, sales in the Korean market in 2021 increased by 22% compared to the previous year [42, 43]. The top four products in sales that led to this increase were probiotics and vitamins. Probiotics showed a steep growth trend across all nutritional product groups, with probiotics increasing by 24.3% and multivitamins by 55.7% compared to the previous year [43]. Louca et al. [6] reported that during the lockdown in the United Kingdom in March 2020, vitamin C and multivitamins sales increased by 110% and 93%, respectively, resulting in a 19.5% increase in the DS market, while the US reported a 415% increase in sales during the 7 days of the peak of the COVID-19 pandemic. Hamulka et al. [32] performed a Google Trend analysis and cross-sectional study during the pandemic and reported increased consumption of vitamins C and D, zinc, omega-3, garlic, ginger, and turmeric during the March 2020 COVID-19 outbreak. A similar trend was also reported by Aysin and Urhan [34].

The results of the semantic network analysis connecting emotion/response to DSs before the COVID-19 pandemic revealed that consumers searching for DSs were thinking about food replacements and wanted to obtain recommendations with high efficacy or effects. They also showed feelings of worry and concern about it. Meanwhile, after the COVID-19 pandemic, consumers were more concerned about functions and side effects in terms of effects and efficacy compared to before. Accordingly, positive keywords related to DS decreased by 0.72% after COVID-19, while negative keywords increased by 0.72%, leading to a decrease in the sub-emotions (joy) of the positive category and an increase in the sub-emotions (pain, fear, and sadness) of the negative category. In this study, the concerns about the function and side effects of DSs after the COVID-19 pandemic and the increased use of negative words can be interpreted in connection with the changes in needs and purposes described above. In other words, as the purpose of DS has changed to infectious disease prevention and treatment, consumers want to obtain information about the effect and efficacy of individual DSs in the COVID-19 pandemic. However, it is difficult to obtain sufficiently reliable information. Thus, negative emotions such as worry and fear increased. In addition, concerns and fear of COVID-19 may have led to the use of DSs. In a situation where a COVID-19 vaccine has already been developed but is not widely used, DSs were commonly used as one way to protect their health during the COVID-19 pandemic. This was linked to an interest in alternative therapies. For example, a study in Saudi Arabia highlighted the growing popularity of ginger, onion, and garlic among the Saudi population because of the belief that they can boost immunity and mitigate the possibility of developing COVID-19 [44]. Moreover, feelings of worry, panic, and anxiety in the medical emergency of the COVID-19 pandemic can lead to a heavy reliance on alternative therapies such as medicinal plants when drug treatment is not yet available [44]. Meanwhile, despite the popularity of DSs in the context of COVID-19, information on their effects and efficacy is insufficient. The Internet plays a pivotal role in health education [45]. The Web provides instant access to a variety of sources and interactions with other users. According to Ayer and Celep [15], who evaluated the use of DSs by Turkish people during the COVID-19 pandemic, 23.4% of respondents said that consumers used social media and the Internet as information sources about DS during the pandemic. Moreover, 90% of young French people perceived the Internet as a reliable source of health-related knowledge [46]. However, while the information consumers obtain leads to the purchase and consumption of DS products, information on social media can be misleading and is sometimes used for business purposes rather than for health promotion communication. Although DSs should be used only after receiving doctor’s advice, Mohsen et al. [3] reported that only 24.8% of the participants took DSs according to the doctor’s prescription. DS misuse and abuse can cause side effects. According to the US Drug-Induced Liver Injury Network, more than 20% of cases of liver damage are reportedly caused by herbs and DSs [47].

While the global DS market is growing significantly as interest in health has increased owing to the recent threat of infectious diseases, the COVID-19 pandemic has led to changes in consumer perception and consumption of DSs. In this context, the present study explored DS-related perception changes and trends before and after the COVID-19 pandemic. These study findings suggest the following industrial and academic implications. First, the big data in this study presented important keywords related to COVID-19 and DS, caused by recent social changes. Behind each of these words is the meaning of implied social change, and it will be necessary for product development and marketing approaches to grasp this closely. For example, in the case of joints, due to reduced physical activity caused by the COVID-19 pandemic, joint diseases in middle-aged and elderly people have worsened, resulting in a demand for nutrients that are good for joints. Lutein is associated with an increased prevalence of myopia owing to decreased outdoor activity and increased screen time after the COVID-19 pandemic. In addition, keywords such as “eyelashes”, “skin”, and “nail” among the results of this study represent DS trends related to beauty. One major recent health-related trend in Korea is the so-called Healthy Pleasure phenomenon. In other words, while the reason for using DSs in the past was ‘to avoid getting sick,’ today’s younger generations use it to ‘be satisfied with their physical condition’ [48]. They take various DSs such as solid stamina, skin beauty, and hair loss prevention; while taking them, they feel satisfied that they are managing themselves. The COVID-19 pandemic and these social trend shifts rapidly changed consumer perceptions and consumption of DSs; therefore, product development and marketing efforts in line with these changes are needed. Since non-face-to-face consumption has been strengthened due to the COVID-19 pandemic and with this change in consumption patterns expected to continue even after the end of the pandemic, the importance of online as a channel for consumers to acquire DS information and purchase will increase [49]. In addition, well-being influencers have recently shared their daily supplement regimens through social media, and followers' purchases of DSs through their sales channels are also increasing [50]. However, since the type and amount of DSs required differ depending on the individual's condition, and excessive intake or the combination of certain medications can cause serious side effects, it is necessary to consult a doctor when using DSs [3]. Concerns about DS function and side effects after the COVID-19 pandemic may be an indication of feelings amid heightened DS use. Therefore, according to the recent DS information acquisition and purchasing environment, the government should support online platforms for easy and accurate access to relevant information on DSs and campaigns to prevent the indiscriminate consumption of DSs.

Unlike previous studies that have conducted empirical research with a limited sample, this study utilized a large amount of big data to compare consumer perceptions of dietary supplements before and after COVID-19 to identify direct changes brought about by the pandemic. This provides inspiration for future research on DS-related consumer behavior after the pandemic. For example, it will be possible to study the differences in changed consumer behaviors between the middle-aged and younger generations seeking ‘healthy pleasure’ DSs after the COVID-19 pandemic, as well as how consumers' DS-related perceptions have changed between before and after the pandemic and after escaping the threat of COVID-19. As an increasing number of consumers are looking for healthy functional foods given individual health conditions, the DS market is also rapidly changing, with the emergence of a customized health functional food market based on genetic test results and technologies, such as artificial intelligence (AI) and big data. Therefore, further research is needed on consumers’ perceptions of self-care and self-treatment using DS. In such research, big data is a good tool to identify changes and trends in consumer perceptions in an objective and comprehensive context, and we believe this paper can provide a good guide.

This study has several limitations. First, this study investigated consumers' DS-related perceptions before and after the COVID-19 pandemic. As this topic is rarely reported, it is difficult to discuss in depth due to the lack of related studies. Second, the big data in this study was extracted from portal site data that is widely used in Korea. Therefore, the results of this study are mainly related to the Korean market as the main consumer base is Korean-speaking consumers. Therefore, based on these limitations, follow-up studies should be conducted by applying relevant data in each country. Even if the targets and research methods used in this study are applied to other countries, different significant results can be drawn only in that country. Third, this study analyzed big data with a rather comprehensive keyword of DSs and it is difficult to understand in detail consumers’ perceptions of individual DSs such as vitamins and probiotics. This topic warrants further investigation through additional big data analyses or qualitative research on individual nutritional supplements.

This study empirically examined consumers’ perceptions and trends in DSs before and after the COVID-19 pandemic through an analysis of big data. Our results provide meaningful clues regarding the DS industry and social changes. Moreover, our findings provide important basic data for understanding consumers after the COVID-19 pandemic in DS consumer-related research fields and industries.

This study identified words closely associated with the keyword DS based on big data in Korean social media and investigated consumers’ perceptions and trends related to DSs before (2019) and after the COVID-19 pandemic (2021). The results were derived through analysis methods such as text mining, semantic networking, network visualization analysis, and sentiment analysis. The DS-related keywords that frequently appeared before and after COVID-19 were “recommend”, “vitamin”, “health”, “children”, “multiple”, and “lactobacillus”. Keywords “calcium”, “lutein”, “skin”, and “immunity” also showed high TF-IDF values. These keywords implied a main interest in DSs among Korean consumers in recent years. The big data results also reflected social phenomena related to DSs; for example, “baby” and “pregnant woman” showed lower TD-IDF values after the pandemic, suggesting lower marriage and birth rates, whereas the higher values for “joint” indicated reduced physical activity due to the COVID-19 pandemic. The semantic network analysis in 2019 formed a network centered on vitamins and health care. However, in 2021, the values were highest for deficiency and need, indicating that individuals were searching for DSs after the COVID-19 pandemic due to a lack of nutrient intake and an awareness of the need. Before the pandemic, DSs and vitamins were related to health care in the life cycle, such as pregnancy; however, after the COVID-19 pandemic, the results of this study confirmed the changed perception has changed to disease prevention and treatment. This study identified meaningful clues regarding consumer perceptions and trends related to DSs before and after COVID-19, providing fundamental data to understand consumers’ post-pandemic in DS consumer-related research fields and industries.