The role of a properly balanced diet in the prevention and treatment of mental disorders has been suggested, while vegetables and fruits have a high content of nutrients that may be of importance in the case of depressive disorders. The aim of the study was to conduct a systematic review of the observational studies analyzing association between fruit and vegetable intake and mental health in adults. The search adhered to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), and the review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42019138148). A search for peer-reviewed observational studies published until June 2019 was performed in PubMed and Web of Science databases, followed by an additional manual search for publications conducted via analyzing the references of the found studies. With respect to the intake of fruit and/or vegetable, studies that assessed the intake of fruits and/or vegetables, or their processed products (e.g., juices), as a measure expressed in grams or as the number of portions were included. Those studies that assessed the general dietary patterns were not included in the present analysis. With respect to mental health, studies that assessed all the aspects of mental health in both healthy participants and subjects with physical health problems were included, but those conducted in groups of patients with intellectual disabilities, dementia, and eating disorders were excluded. To assess bias, the Newcastle–Ottawa Scale (NOS) was applied. A total of 5911 studies were independently extracted by 2 researchers and verified if they met the inclusion criteria using a 2-stage procedure (based on the title, based on the abstract). After reviewing the full text, a total of 61 studies were selected. A narrative synthesis of the findings from the included studies was performed, which was structured around the type of outcome. The studies included mainly focused on depression and depressive symptoms, but also other characteristics ranging from general and mental well-being, quality of life, sleep quality, life satisfaction, flourishing, mood, self-efficacy, curiosity, creativity, optimism, self-esteem, stress, nervousness, or happiness, to anxiety, minor psychiatric disorders, distress, or attempted suicide, were analyzed. The most prominent results indicated that high total intake of fruits and vegetables, and some of their specific subgroups including berries, citrus, and green leafy vegetables, may promote higher levels of optimism and self-efficacy, as well as reduce the level of psychological distress, ambiguity, and cancer fatalism, and protect against depressive symptoms. However, it must be indicated that the studies included were conducted using various methodologies and in different populations, so their results were not always sufficiently comparable, which is a limitation. Taken together, it can be concluded that fruits and/or vegetables, and some of their specific subgroups, as well as processed fruits and vegetables, seems to have a positive influence on mental health, as stated in the vast majority of the included studies. Therefore, the general recommendation to consume at least 5 portions of fruit and vegetables a day may be beneficial also for mental health.

During the coronavirus-19 disease (COVID-19) pandemic, the basic strategy that is recommended to reduce the spread of the disease is to practice proper hand hygiene and personal protective behaviors, but among adolescents, low adherence is common. The present study aimed to assess the gender-dependent hand hygiene and personal protective behaviors in a national sample of Polish adolescents. The Polish Adolescents’ COVID-19 Experience (PLACE-19) Study was conducted in a group of 2323 secondary school students (814 males, 1509 females). Schools were chosen based on the random quota sampling procedure. The participants were surveyed to assess their knowledge and beliefs associated with hand hygiene and personal protection, as well as their actual behaviors during the COVID-19 pandemic. The majority of respondents gave proper answers when asked about their knowledge. However, females displayed a higher level of knowledge (p < 0.05). Most of the respondents declared not leaving home, handwashing, using alcohol-based hand rub, avoiding contact with those who may be sick, and avoiding public places as their personal protective behaviors. They declared using face masks and gloves after the legal regulation requiring people to cover their nose and mouth in public places was enacted in Poland. Regarding the use of face masks and not touching the face, no gender-dependent differences were observed, while for all the other behaviors, females declared more adherence than males (p < 0.05). Females also declared a higher daily frequency of handwashing (p < 0.0001) and washing their hands always when necessary more often than males (68.2% vs. 54.1%; p < 0.0001). Males more often indicated various reasons for not handwashing, including that there is no need to do it, they do not feel like doing it, they have no time to do it, or they forget about it (p < 0.0001), while females pointed out side effects (e.g., skin problems) as the reason (p = 0.0278). Females more often declared handwashing in circumstances associated with socializing, being exposed to contact with other people and health (p < 0.05), and declared always including the recommended steps in their handwashing procedure (p < 0.05). The results showed that female secondary school students exhibited a higher level of knowledge on hand hygiene and personal protection, as well as better behaviors, compared to males. However, irrespective of gender, some false beliefs and improper behaviors were observed, which suggests that education is necessary, especially in the period of the COVID-19 pandemic.

Due to the COVID-19 pandemic, the World Health Organization and other major authorities recommend frequent hand washing and applying proper hand hygiene procedures as one of the cheapest, easiest, and most important ways to prevent the spread of a virus. For adolescents it is especially important as it should become for them a lifelong habit. The aim of the study was to assess the hand hygiene behaviors during the COVID-19 pandemic in a national Polish sample of secondary school adolescents and to verify the influence of the COVID-19 pandemic on those behaviors. The study was conducted in April 2020 in a national sample of 2323 secondary school students recruited based on secondary school sampling procedure (random quota sampling with quotas for voivodeships). The hand hygiene behaviors that were assessed included: frequency of washing hands, reasons for not washing hands, circumstances of washing hands, and procedure of handwashing. Participants were asked each question twice—for the current period of the COVID-19 pandemic and for the period before the COVID-19 issue. The declared frequency of washing hands during the COVID-19 pandemic was significantly higher than before (p < 0.0001), as the majority of respondents declared doing it 6–15 times a day (58.4%) while before the pandemic, it was 3–10 times a day (68.1%). The share of respondents declaring washing their hands always while it would be needed was significantly higher for the period during the COVID-19 pandemic (54.8%) than it was for the period before (35.6%; p < 0.0001), and there was a lower share of respondents declaring various reasons for not washing hands. For the majority of circumstances of washing hands, including those associated with meals, personal hygiene, leaving home, socializing, health, and household chores, the share of respondents declaring always washing their hands was significantly higher for the period during the COVID-19 pandemic than for the period before (p < 0.0001). For the majority of steps of handwashing procedure, the share of respondents declaring including them always was significantly higher for the period during the COVID-19 pandemic than for the period before (p < 0.0001), but a higher share declared not wearing a watch and bracelet (p = 0.0006), and rings (p = 0.0129). It was concluded that during the COVID-19 pandemic all the assessed hand hygiene behaviors of Polish adolescents were improved, compared with those before, but hand hygiene education is still necessary.

A potential role of vitamin D in some components of mental health is currently suggested, but the analyses are conducted mainly for adults, while for young individuals mental health is especially important, due to its lifelong effects. The aim of the study was to analyze the association between vitamin D intake or status and mental health in children within a systematic review of literature, including both intervention and observational studies. The literature search was conducted according to the PRISMA guidelines and it covered peer-reviewed studies included in databases of PubMed and Web of Science until October 2019. The studies presenting either vitamin D intake, or vitamin D status in human subjects were allowed (excluding subjects with intellectual disabilities, eating disorders and neurological disorders), while for mental health the various methods of assessment and wide scope of factors were included. The bias was assessed using the Newcastle–Ottawa Scale (NOS). The review was registered in the PROSPERO database (CRD42020155779). A number of 7613 studies after duplicate removing were extracted by two independent researchers, followed by screening and assessment for eligibility, conducted by two independent researchers in two steps (based on title and abstract). Afterwards, the full texts were obtained and after reviewing, a number of 24 studies were included. The synthetic description of the results was prepared, structured around exposure (vitamin D supplementation/status) and outcome (components of mental health). The included studies were conducted either in groups of healthy individuals, or individuals with mental health problems, and they assessed following issues: behavior problems, violence behaviors, anxiety, depressive symptoms/depression, aggressive disorder, psychotic features, bipolar disorder, obsessive compulsive disorder, suicidal incident, as well as general patterns, as follows: mental health, level of distress, quality of life, well-being, mood, sleep patterns. The vast majority of assessed studies, including the most prominent ones (based on the NOS score) supported potential positive influence of vitamin D on mental health in children. As a limitation of the analysis, it should be indicated that studies conducted so far presented various studied groups, outcomes and psychological measures, so more studies are necessary to facilitate comparisons and deepen the observations. Nevertheless, vitamin D intake within a properly balanced diet or as a supplementation, except for a safe sun exposure, should be indicated as an element supporting mental health in children, so it should be recommended to meet the required 25(OH)cholecalciferol blood level in order to prevent or alleviate mental health problems.

During the outbreak of Coronavirus Disease 2019 (COVID-19) pandemic and the lockdown, various changes of dietary habits are observed, including both positive and negative ones. However, the food choice determinants in this period were not studied so far for children and adolescents. The study aimed to analyze the changes in the food choice determinants of secondary school students in a national sample of Polish adolescents within the Polish Adolescents’ COVID-19 Experience (PLACE-19) Study population. The study was conducted in May 2020, based on the random quota sampling of schools (for voivodeships and counties) and a number of 2448 students from all the regions of Poland participated. The Food Choice Questionnaire (FCQ) (36 items) was applied twice—to analyze separately current choices (during the period of COVID-19 pandemic) and general choices (when there was no COVID-19 pandemic). For both the period before and during the COVID-19 pandemic, sensory appeal and price were indicated as the most important factors (with the highest scores). However, differences were observed between the scores of specific factors, while health (p < 0.0001) and weight control (p < 0.0001) were declared as more important during the period of COVID-19 pandemic, compared with the period before, but mood (p < 0.0001) and sensory appeal (p < 0.0001) as less important. The observations were confirmed for sub-groups, while female and male respondents were analyzed separately. It can be concluded that the COVID-19 pandemic may have changed the food choice determinants of Polish adolescents, as it may have increased the importance of health and weight control, but reduced the role of mood and sensory appeal. This may be interpreted as positive changes promoting the uptake of a better diet than in the period before the pandemic.