INTRODUCTION
The COVID-19 pandemic, caused by the coronavirus SARS-CoV-2, has strongly influenced the health of populations worldwide and lifestyle behaviors [1]. Among several changes in lifestyle behaviors, dietary habits such as emotional eating, increased snacking frequency (sweet or salty snacks), increased alcoholic beverage consumption, increased consumption of processed foods, and decreased water intake have been reported [2, 3]. These changes in nutrition and additional factors related to the lockdown, such as increased sedentary behaviors, decreased physical activity, disturbed sleep patterns, poor sleep quality, anxiety, and stress, have influenced lifestyle-related behaviors and nutrition. Also, social isolation was strongly associated with increased consumption of carbohydrates and fats, which poses a challenge to maintaining public health and optimal nutritional status. Consumption of high-calorie food with limited physical activity may have long-term effects and increase body weight [4, 5].
Some studies reported favorable changes in the nutrition and lifestyle of our society during the COVID-19 pandemic, including an increase in fresh produce consumption, more time for home cooking, and reductions in comfort food and alcohol consumption [6]. However, heterogeneous methodology and various research tools used to assess dietary patterns and nutritional behavior do not allow for the comparison of data and simple conclusions.
The impact of COVID-19 infection on lifestyle behavior varies from country to country due to several social, cultural, and economic factors. Many studies have been conducted on dietary changes during the COVID-19 pandemic among adults in Poland. However, to our knowledge, no systematic review or meta-analysis has synthesized changes in Poles’ nutrition and lifestyle behavior during the pandemic. Therefore, this study aimed to assess the impact of the pandemic on the favorable and unfavorable nutritional behaviors of the adult population in Poland.
METHODS
The systematic review and meta-analysis were conducted based on the Preferred Reporting Items for Systematic (PRISMA) protocol [7] and the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines [8]. Using the PECOS strategy, we developed the research question and preliminary inclusion and exclusion criteria of the study (Table 1).
LITERATURE SEARCH STRATEGY
The articles included in this review were identified by searching four electronic databases: Scopus, Web of Science, PubMed, and Polish AGRO Base. This search was undertaken between 1st January 2020 and May 31st 2024. The keywords used in all databases were the same: “Poland” AND “COVID-19” AND “change*” AND “diet*”. The following filters were used in the search: all fields; country: Poland; affiliation: Poland; language: Polish and English; and document type: reviews were excluded. The search terms were checked by a librarian with a background in the nutrition field (MS). Initially, 1226 records were identified in this way. The searched records were exported as individual databases to Excel and sorted using automation software tools. Duplicates and records marked as ineligible were removed using hand searching.
STUDY SELECTION PROCESS AND ELIGIBILITY CRITERIA
The assessment was performed independently by two reviewers (AH, BS) in a stepwise manner. A third senior researcher (DG) resolved disagreements and disputes based on appropriate guidelines [9]. In the case of missing data, the authors of selected articles were contacted directly to obtain baseline data. At first selection, keywords were used to search abstracts and titles according to eligibility criteria. Records that did not meet eligibility criteria were excluded (n = 125). In the next step, only full-text articles were assessed for eligibility based on the preliminary inclusion and exclusion criteria (Table 1) and additional criteria as described in Figure 1. Records that did not meet eligibility criteria were excluded (n = 20).
Finally, 21 articles [10-30] were included in the review (qualitative assessment), and 8 studies [12, 13, 15, 17, 21, 23, 24, 29] were included in the meta-analysis (quantitative analysis). Figure 1 presents the study selection process, showing the inclusion and exclusion of studies throughout the systematic review protocol and the inclusion of studies in the meta-analysis, as a PRISMA [7] diagram. The review protocol was not registered.
DATA EXTRACTION AND SYNTHESIS
Two authors (AH, DG) completed data extractions using a custom-created extraction chart that included the author/s and year, study type, exposure time/data collection, population, sample size, age of participants, method of dietary assessment, and main study findings (Supplementary Table S1).
DATA SYNTHESIS FOR SYSTEMATIC REVIEW
Data synthesis for the systematic review of studies included in this part (n = 21) consisted of collecting data on changes in food consumption, expressed as intake or frequency, and self-reported changes during the COVID-19 pandemic (increased/decreased consumption, no changes in consumption).
FOOD GROUP CLASSIFICATION
According to the purpose of this study, all food groups were categorized into two groups:
1. Pro-healthy food, including: grain and cereal products (bread, pasta, rice, cereals, and wheat); legumes/pulses (including beans, seeds, pulses, and nuts); potatoes; vegetables; fruits; milk and dairy products (fermented milk products, and cheese); eggs; white meat; fish and seafood; vegetable fats, and water (mineral and tap water).
2. Less healthy food, including: red meat; processed meat; animal fats; fast food; salty snacks (salty and savory snack foods, chips, sticks, popcorn); sweets and sugar (total sweet products, homemade and commercial pastry, confectionary products, candy, ice cream, pudding and sugar); energy drinks (EDs); juices (fruits and vegetable juice with or without added sugar/salt); sugar- sweetened beverages (SSBs), and alcohol.
This assignment to groups and classification was done by the dietitian (BS) according to the Polish recommendations “A plate of healthy eating” [31]. Analysis of the changes in intake of other products such as homemade meals, takeaway meals, ultra-processed foods, and dietary supplements was conducted. Additionally, eating behaviors such as the number of meals, regularity of food consumption, and eating breakfast were analyzed.
QUALITY ASSESSMENT AND RISK OF BIAS
Study quality was assessed using the Newcastle- Ottawa Scale (NOS) [32], adapted for cross-sectional studies, which was modified for this study [3]. Study quality was assessed by two authors (AH and DG), who completed the quality assessment independently for all studies, with disagreements resolved via discussion (Supplementary Table S2).
DATA SYNTHESIS FOR META-ANALYSIS – EFFECT MEASURES
The analysis presented in the study was performed using the R program version 4.2.2 [33] with the use of RStudio version 2022.12.0 [34]. The overall proportions from studies reporting a single proportion were calculated using the meta prop procedure from the meta package [35], created explicitly for the meta-analysis. The random effect models were analyzed. The inverse variance method was applied for the pooling of the single proportions. The forest, lollipop and the Cleveland dot plots, generated with the ggplot2 package [36], were used to graphically compare results for the studied food products.
RESULTS
SYSTEMATIC REVIEW RESULTS
Out of 1226 initially identified papers, 21 articles [10-30] were included in the systematic review (Figure 1). More details are presented in Supplementary Table S1.
METHODS OF FOOD INTAKE ASSESSMENT
Analyzed studies used different methods to assess changes in dietary patterns and eating behavior, making it difficult to compare results between studies. Four studies used a food frequency questionnaire (FFQ) [11, 20, 22, 28], 16 studies used study-specific questionnaires [12-19, 21, 23-27, 29, 30], and one study [10] combined study-specific and food frequency methods. Six questionnaires were validated [11, 20-23, 28]. The number of food products being assessed and their categorization varied between studies and were determined by the purpose of the study. In studies using an FFQ, the number of group products varied from 6 items [22, 28] to 111 items [20]. One study analyzed changes in the consumption of specific foods – meat and meat products, as well as fish and seafood [29]. More details are presented in Supplementary Table S1.
CHANGES IN CONSUMPTION OF PRO-HEALTHY FOOD, LESS HEALTHY FOOD, AND OTHER NUTRITIONAL BEHAVIORS
Grain and cereal products
Ten of the 21 included studies (48%) analyzed changes in the consumption of grain and cereal products [10, 11, 13, 15, 16, 21, 22, 26, 28, 30]. Among these 10 studies, 3 found an increase in consumption [16, 22, 26], and one in the frequency of consumption [28]. Three studies identified statistically significant changes [22, 26, 28]. One study found a significant decrease in daily servings of bakery products [11]. No changes were found in 4 studies: in consumption [13] and in the frequency of consumption [10, 11, 30]. In two studies [15, 21], over 60% of respondents reported no changes in grain and cereal consumption.
Legumes/pulses, nuts/seeds, and potatoes
Five studies (24%) investigated changes in legume/pulse intake [11, 13, 15, 23, 24]. Only 1 study reported no change in the frequency of consumption and daily servings of pulse intake [11]. In 4 studies [13, 15, 23, 24] related to the structure of legume consumption, an average of 75% of respondents reported no changes. Statistically significant changes were found in one study [15].
Two out of 21 studies (10%) analyzed changes in nut intake [26, 30], and 2 other studies (10%) analyzed changes in potato consumption [11, 21]. Among 2 studies related to nut intake, one reported a significant increase in consumption [26], while another study [30] found no change in frequency of consumption. Two studies on potato consumption [11, 21] identified an increase in consumption.
Vegetables
Twelve studies (57%) analyzed changes in vegetable consumption [10, 11, 13, 15, 16, 18, 21-24, 28, 30]. Among these 12 studies, 3 found an increase in consumption [16, 18] or a significant increase in the frequency of consumption of vegetables [28]. One study demonstrated lower intake [21]. Three studies [10, 11, 22] found no changes in consumption [22], and no changes in the frequency or daily servings of vegetables [10, 11]. In one study [13], over 40% of respondents reported no changes, in 4 others [15, 22-24], at least 60%. One study [30] noted a significant change in the frequency of vegetable consumption, but it is not clear whether an increase or decrease was found.
Fruits
Thirteen studies (62%) analyzed changes in fruit consumption [10, 11, 13, 15, 16, 18, 21-24, 26, 28, 30]. Four studies found an increase in consumption [16, 18, 21, 26] or in frequency of consumption [28], but only one study found statistically significant changes [26]. None of the 13 studies showed a decrease in fruit consumption. Four studies showed no change in consumption [22], or in the frequency of consumption [10, 11, 30]. In the remaining studies [13, 15, 23], over 50% of respondents reported no changes in fruit consumption, and in one study [24], as many as 82% of respondents reported no changes.
Milk and dairy products
Ten studies (48%) analyzed changes in consumption of milk and dairy products [11, 13, 15, 16, 21, 22, 24, 26, 28, 30]. Among these 10 studies, 3 found an increase in consumption [16, 26] and a significant increase in frequency of consumption [28]. None of the studies showed a decrease in consumption. Two studies found no change in consumption [22] and no change in frequency and daily servings [11]. Four studies, in which the structure of consumption was assessed, showed that at least 58% of people indicated no change [13, 15, 21]. In another study [24], no change was noted in almost 90% of subjects. In the last study [30], the authors found a significant change in the frequency of consumption, but the direction of change is not clear.
Eggs
Six studies (29%) analyzed changes in egg consumption [11, 13, 16, 21, 24, 26]. Among these 6 studies, 3 found an increase in consumption [16, 26] and statistically significantly more frequent consumption [11]. None of the studies found a decrease. In 3 studies, more than 50% of respondents did not report any changes [13, 21], and in one case, more than 90% [24].
Meat and meat products
Thirteen studies (62%) analyzed changes in meat and product consumption [10, 11, 13-16, 21-24, 26, 28, 29]. The analyzed group of products was diverse; the authors referred to meat and meat products in general, red and white meat separately, and processed meat. One study was about low-fat meat [15].
Among all these 13 studies, no increase in the consumption of meat and meat products in general was noted. Five studies found a decrease in consumption [14, 16, 26] and in frequency of consumption in general [28], and one study noted decreased intake of red meat [11]. The changes indicated in 2 studies were significant [11, 14]. Two studies found no change in consumption [22] and in frequency of consumption in general [10]. In one study, no change in the frequency of daily servings of white meat was observed [11]. In 4 studies, at least 50% of respondents reported no change [13, 21, 23, 29], and in another study [24], almost 90% of respondents reported no change. In one study, in which the consumption of low-fat meat and processed meat was analyzed, over 70% of respondents reported no change [15].
Fish
Thirteen studies (62%) analyzed changes in consumption of fish [10, 11, 13, 15, 16, 21-24, 26, 28-30]. Among these 13 studies, only one [26] identified an increase in consumption (it was statistically significant). Two studies found a decrease in consumption and frequency of consumption [16, 28]. Four studies found no change in consumption [22] and frequency of consumption [10, 11, 30]. In 6 studies, the highest percentage of respondents indicated no change: in 3 studies over 50% of respondents [13, 21, 29], in one study over 70% of respondents [15, 23], and the last study almost 90% of respondents [24].
Fats (animal/vegetable)
Five studies (24%) analyzed changes in fat (animal/vegetable) consumption [11, 21-23, 28]. In the studies, the authors referred to fats (in general) or separately to animal and vegetable fats.
Among those 5 studies, one study [28] found a significantly increased frequency of fat consumption, and significantly reduced consumption of fats was noted in another study [22].
No change in frequency and daily servings of butter, lard, and oils/margarines was observed in one study [11]. In another study [23], the majority of subjects (83%) reported no change in intake of olive oil. The last study [21], where the authors analyzed animal and vegetable fats separately, revealed increased consumption of animal fats (62% of respondents reported higher intake), and no change in consumption of vegetable fats (72% of respondents).
Water
Eight studies (38%) analyzed changes in water consumption [11, 13, 15, 18, 21, 25, 26, 28]. Among these 8 studies, 3 found an increase in consumption [25, 26] and in frequency of consumption [28]; one of them was significant [26]. None of these studies revealed a decrease. One study found no change in frequency and daily servings [11]. In the case of 3 studies, over 40% of respondents [13, 15, 21] reported no change in water drinking. In one study, over 50% of subjects reported drinking at least 1.5 l water per day [18].
Fast food
Eight studies (38%) analyzed changes in fast food intake [10-13, 15, 18, 20, 30]. Among these 8 studies, only one found more frequent consumption (it was statistically significant) [20]. The next study showed that 8.5% of subjects ate a lot of fast food [18]. Two studies [11, 13] found decreased consumption and less frequent consumption or fewer daily servings of fast food; all studies were significant. Two studies [10, 30] found no change in the frequency of consumption. In the remaining 2 studies [12, 15], over 44% of the respondents reported no change in fast food consumption.
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Salty snacks
Five studies (24%) analyzed changes in salty snack intake [12, 13, 15, 21, 30]. Among these 5 studies, no study found increased consumption. In one study [21], 58% of respondents reported lower consumption of salty snacks. No changes in the frequency of consumption were reported in one study [30]. In other studies, the highest percentage of subjects reported no change, over 40% of respondents in 2 studies [12, 13]. In one study [15], over 60% of respondents stated that their consumption of salty snacks during the pandemic period compared to before did not change.
Sweets and sugar
Thirteen studies (62%) analyzed changes in sweets and sugar consumption [10-13, 15, 17, 18, 21-23, 26, 28, 30]. Among these 13 studies, 4 found increased consumption and more frequent intake [11, 21, 26, 28], 2 of which were statistically significant. One study identified a decrease in the consumption of sweets and sugar [22]. Two studies found no change [10, 30]. In 5 studies, no change was reported by about 40% of respondents [12, 13], and in the next 3 studies [15, 17, 23], more than 50% of respondents stated that their consumption during the COVID-19 pandemic period was the same as before.
Energy drinks
Five studies (24%) analyzed changes in energy drinks (EDs) consumption [11, 13, 15, 20, 30]. Among these 5 studies, 1 [20] found more frequent consumption of EDs, and 2 [11, 30] found less frequent consumption of such drinks; all such changes were significant. One study found that about 40% of the total subjects did not drink EDs during the pandemic [13]. In the last study, over 90% of respondents reported no change in ED consumption during the pandemic period [15].
Juices and SSBs
Twelve studies (57%) analyzed changes in juice and SSB consumption [11-13, 15, 18, 19, 21-23, 25, 26, 28]. Products of these groups (juices and SSBs separately) were defined differently by the authors in the studies, and their nomenclature and categorization were not always consistent with WHO recommendations, including for SSBs products [37]. Interpretation of the data required great caution.
Among 4 studies related to some kinds of juice [11, 19, 21, 22], 3 found no change [11, 21, 22]. In the case of one study [21], as many as 56% of respondents reported no change in consumption of juices. In another study [19], 12.7% of respondents stated that they drank juice every day.
Among studies that assessed changes in SSB consumption, one [18] found that almost 60% of respondents avoided such soft drinks. Two studies found increased intake of carbonated acid beverages [25] and an increase in the frequency of their consumption [28]. Two studies found a decrease in consumption of SSBs [26] and fewer daily servings of them [11]. No change in the frequency of SSB consumption was reported in one study [22]. In the remaining studies, the highest percentage of respondents reported no change in SSB consumption during the COVID-19 pandemic. In 4 studies [12, 13, 21, 23], it was over 40% of respondents, and in one study, over 85% of the total group [15].
Alcohol
Fifteen studies (71%) analyzed changes in alcohol intake [10-13, 15, 20-28, 30]. Among these studies, 6 found an increase in consumption and an increase in the frequency of alcohol consumption [11, 21, 25, 27, 28, 30], but only one was significant. In one study [21], changes in consumption were related to the level of the subject’s anxiety due to COVID-19. Five studies [13, 20, 22, 24, 26] found a decrease in consumption and its frequency, in 3 cases [13, 20, 22] it was significant, and in one the difference was gender-related [13]. Two studies [10, 11] found no change in the consumption of alcohol. In 3 other studies [12, 15, 23], the highest percentage of subjects reported no change in alcohol consumption.
Dietary supplements, homemade and takeaway meals
Five studies (24%) analyzed changes in dietary supplement intake [11, 17, 18, 21, 24] and found greater [17, 21] or regular [18] use of many supplements during the pandemic period. The most popular supplements were vitamins D, C, A, E, and group B vitamins, minerals Mg, Zn, Fe, and omega-3 fatty acids. One study noted that men used supplements more often than women [24]. Another study [21] found correlations with COVID-19 anxiety; people with higher anxiety reported greater use of supplements. Two studies analyzed takeaway meal intake [10, 12], and two studies examined homemade meals [13, 15] (over 40% increase). Ultra-processed foods such as canned and instant products were discussed in one study [11], which reported lower consumption of instant soups and higher consumption of canned meat.
Nutritional behaviors – number of meals, regularity, and eating breakfast
Eight studies (38%) analyzed changes in the number of meals [10, 11, 17-20, 24, 30], 5 out of 21 (24%) in regularity [16, 18, 20, 21], and 2 out of 21 (10%) in breakfast consumption [27, 30]. Five studies related to the number of meals found an increase in their number in the daily menu or an increase in the percentage of people eating 5 or more meals per day [11, 17, 19]; 2 of them were significant. One study found a decrease [30], and 2 studies found no change [10, 20]. Regarding regularity, 2 studies [16, 21] found more regularity, in 1 case related to women compared to men [16]. Regarding eating breakfast, all analyzed studies [27, 30] found that it was more frequent during the COVID-19 pandemic than in the past. Data from one study showed that adherence to healthy diet recommendations, such as eating more regularly, was better in the group of people with a higher level of anxiety due to the COVID-19 pandemic compared to the other study groups (with lower and moderate levels of anxiety due to the COVID-19 pandemic) [21].
META-ANALYSIS RESULTS
The results of the meta-analysis are presented in Figures 2-4 and in Supplementary Figures S1-S3. Both favorable and unfavorable changes were reported by adults in Poland in consuming food products during the COVID-19 pandemic. Beneficial changes covered increases in consumption of vegetables (22% of participants), fruits (24%), and milk and dairy products (19%) (Figure 2 and Supplementary Figure S1), and decreases in consumption of fast food (47%), and SSBs (26%) (Figure 3 and Supplementary Figure S2). An increase in water consumption (33%) and a decrease in juice consumption (31%) were reported.
Unfavorable changes comprised reduced consumption of fish (18%) (Figure 2 and Supplementary Figure S1) and increased consumption of sweets and sugar (31%) (Figure 3 and Supplementary Figure S2). Moreover, there was an increase in the use of dietary supplements (56%) and greater consumption of homemade meals (48%), while takeaway meals were reduced (37%). It is worth emphasizing that a large percentage of respondents did not change their eating behavior, whether those considered pro-healthy or those less healthy (Figure 4 and Supplementary Figure S3).
DISCUSSION
The COVID-19 pandemic has resulted in many significant changes in various areas of life, including eating behavior. In this paper, we describe a systematic review and meta-analysis to answer the research question: What dietary changes were observed during the COVID-19 pandemic among adults in Poland? The results of this study showed both healthy and unhealthy diet-related behavior.
CHANGES IN DIET RELATED TO HEALTH-PROMOTING FOOD
As favorable changes in this meta-analysis, we identified an increase in the consumption of vegetables, fruits, water, milk, and dairy products. During lockdown, many Poles made more conscious choices about food products. These aspects were indicated by the authors of studies included in this review [11, 16, 21].
An increase in the consumption of vegetables and fruits during the COVID-19 pandemic was found as one of the most important dietary changes in this meta- analysis. Higher vegetable consumption during the pandemic has been observed in other studies [38]. Plant foods are important sources of vitamins, minerals, and phytochemicals with anti-inflammatory properties and a strong impact on the proper function of the immune system [39]. An optimal intake of vegetables and fruits was found to be correlated with a lower risk of heart disease [40], the most common cause of death during the COVID-19 pandemic [41]. Vegetable consumption was inversely associated with stress, anxiety, and depression. Furthermore, vegetables and fruits are rich in dietary fiber, which helps to maintain a healthy body weight. Nutritional and body weight status of the Polish population has been the subject of many studies during the COVID-19 pandemic [4, 5]. Also, in the studies included in this review, the authors analyzed body mass changes during the pandemic period regarding the consumption of selected product groups [12, 13, 22, 27, 29].
Not all studies confirm this positive trend in vegetable and fruit consumption during the COVID-19 pandemic. Lower intake of these products was related to food security status and poor diet [42]. Respondents who reduced their purchases of fresh fruit and vegetables gave several reasons: low quality, poor availability, fewer visits to stores, concerns about contamination, and high prices. It should be noted that in Poland, a significant increase in prices of vegetables and fruits, which is quite commonly attributed to COVID-19, took place before the pandemic in 2019 [43]. The same authors confirmed that the prices of selected products (e.g., citrus fruits) increased slightly (by around 10%) in Poland during the pandemic in response to increased demand resulting from greater consumer interest in healthy products.
In Iran and Kenya, high food prices during the COVID pandemic, threats, and lack of stability in terms of food security contributed to a decrease in the consumption of milk and dairy products [44, 45]. In contrast, an increase in consumption of milk and dairy products, a similar trend to our results, was recorded in Brazil [46, 47]. The authors of the Brazilian study found that despite the increase in the prices of dairy products, their consumption increased, which resulted from the fact that consumers were very aware of the benefits of their consumption.
Fish consumption in Poland is low, and during the COVID-19 pandemic a decline in fish consumption was observed. The latest study revealed that 80% of respondents consumed fish less frequently than recommended [48]. Fish are a source of protein, omega-3 fatty acids, vitamin D, and iodine, and should be an essential component of a healthy diet [31]. The decline in fish consumption during the COVID-19 pandemic may be related to their limited availability, especially of fresh products in shops, and disruptions in supply chains or their prices [43]. Perhaps the reduced fish consumption detected in the studies included in this meta-analysis was related to the fact that consumers during the COVID-19 pandemic were more likely to choose products with a longer shelf life. Concerns about the safety of food, especially imported food (including fish), may also have contributed to the decline in consumption.
CHANGES IN DIET RELATED TO LESS HEALTHY FOOD PRODUCTS
A greater intake of sweets and sugar during the pandemic period was found in our meta-analysis. Higher consumption of sugar and sweets during the pandemic has also been observed in other studies [48, 49]. This dietary behavior may be related to the increased stress that the public experienced in isolation during the COVID-19 pandemic. Increased intake of sweets and other unhealthy sugar-containing products is a mood-booster and a panacea for anxiety. The authors of one of the studies included in the review and meta-analysis described differential eating behaviors according to anxiety levels and COVID-19 symptoms [21].
One of the beneficial dietary behaviors of Poles during the pandemic was lower consumption of fast food and sweetened beverages. Many studies have confirmed these results [2, 10, 11, 18, 20, 25, 26, 28, 30]. This situation was connected with increased health awareness [2], and a change in lifestyle and daily routine in general [47]. The reduction in outdoor activities and the closure of gyms resulted in a decrease in physical activity for many people. This led to conscious avoidance of high-calorie foods such as fast food and SSBs to maintain a healthy body weight [2, 47]. Limited consumption of fast food and SSB was a mechanism for maintaining health in general and also coping with stress [47]. Another aspect that authors emphasized was the issue of social isolation and the impact of lockdown [2]. Lockdown and social distancing measures reduced access to fast food bars, leading to a decline in consumption. Increased consumption of homemade meals and a decrease in takeaway meals were noted in our meta-analysis. Another study [50] confirmed that during the COVID-19 pandemic, consumers were more likely to choose to eat at home due to several reasons; among them, concerns about health safety and the risk of infection in public places led to avoiding restaurants and bars. Additionally, restrictions on the functioning of catering and lockdowns meant that many people started to prepare meals themselves. Such meal preparation methods, compared to takeaway meals, allowed better control of the nutritional value and composition of meals as well as being cheaper [50]. Negative aspects of cooking at home were also highlighted [50]. Families spent more time preparing and eating meals, which resulted in overconsumption of food. Having more free time was also conducive to increased snacking in families (e.g., high-calorie snacks, desserts, and sweets), and parents became more indulgent towards their children.
In the present meta-analysis, overall less frequent use of ultra-processed foods was observed, but consumption of canned foods was higher [11]. In our opinion, the lower interest in ultra-processed food is due to the greater awareness of respondents, as described above, and the greater interest in canned food was related to its shelf life and suitability for consumption. During the COVID-19 pandemic, we observed trade restrictions and a period of shortages of products, which resulted in people stockpiling food, e.g., in canned form. Moreover, such food may be associated with greater microbiological safety.
In this study, we also noted the use of supplementation, especially vitamins D and C, omega-3 fatty acids, zinc, and probiotics. Supplement use was correlated with fear of COVID-19 [21]. However, unjustified overuse of dietary supplements, without the supervision of a physician or dietitian, may be dangerous. Polish recommendations indicate only regular vitamin D supplementation.
In summary, this systematic review’s results provide evidence for healthy and less healthy consumer behavior during the COVID-19 pandemic in Poland. Our meta-analysis of cross-sectional studies revealed increased food consumption during the pandemic (vegetables, fruits, water, milk, and dairy products), which we rated as beneficial for health. It is worth emphasizing that many Poles did not change their eating behavior during the COVID-19 pandemic, including meat, legumes and pulses, plant oils, and alcohol intake.
STRENGTHS AND LIMITATIONS OF THE STUDY
This is the first systematic review and meta-analysis we know of that describes the changes in food intake during the COVID-19 pandemic among Polish adults. The strength of the study is the fact that a systematic review and meta-analysis were conducted based on PRISMA and MOOSE protocols [7, 8].
However, this review has some limitations, mainly due to the quality of the studies included in the analysis. Limitations included the different methods of assessing changes in food consumption (FFQ versus study-specific questionnaire); not always validated tools; the highly variable sample size; the lack of representativeness of the sample; the imbalance by gender (predominantly female); poorly described and not clear study protocol; heterogeneity of food group classification; variation in the number of food products being analyzed (6 foods vs. 111); and diverse categorizations of food frequency consumption.
In addition, we did not include studies that investigated nutrient intake (quantitative studies), as they would not be comparable with studies assessing only changes in food intake (qualitative studies). The observational nature of studies included in this meta-analysis and high heterogeneity observed among studies challenge the interpretation of the results.
CONCLUSIONS
According to the WHO recommendation, good nutrition is very important before, during, and after a COVID-19 infection. There is no diet to prevent or treat COVID-19. However, growing evidence supports the importance of eating a healthy diet, being physically active, managing stress, and following healthy sleeping patterns as a first line of anti-viral defense. Both positive and negative changes in eating behaviors during the COVID-19 pandemic were observed among adults in Poland. Future studies that assess nutrient intake at individual and population levels are important to measure the impact of dietary changes during the pandemic on health status.
ACKNOWLEDGMENT
Authors of the article would like to thank Mrs. Magdalena Seta, Ph.D., Head of the Scientific Information Department and the Team of this Department as employees of the Władysław Grabski Main Library, Warsaw University of Life Sciences (WULS-SGGW), for their commitment and help in searching for literature.
DISCLOSURES
The authors report no conflict of interest.
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