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.

The effect of dietary fat level and composition on the activities of enzymes involved in thyroid hormone metabolism: thyroid peroxidase (TPO) and hepatic type I deiodinase (DI) were investigated. Male Wistar rats weighing on average 277 g (SEM=4.23 g) received different levels (w/w 5%-LF, 10%-MF, 20%-HF) and types of dietary fat (sunfl ower oil -group S, rape seed oil -R and palm oil -P) over a three weeks. TPO rose with fat intake in group R and declined in groups S and P. Hepatic DI activity was not affected by dietary fat composition, but was infl uenced by fat level, decreasing as fat intake increased. The infl uences of dietary fat level and composition on thyroid physiology are interdependent. TPO and DI activity seem to respond in a differentiated manner to changes in the amount and type of fatty acids consumed.

Thyroid hormones (TH) are essential for the normal development and function of every vertebrate. The hypothalamic-pituitary-thyroid (HPT) axis is regulated to maintain euthyroid status. One of the most influential environmental factors that determines HPT axis activity is nutrition. Both food availability and substrate diversity affect thyroid hormone economy. The present paper aims to summarize literature data concerning the influence of the amount and the type of protein on thyroid axis activity. This review sheds light on the contribution of a low-protein diet or insufficient intake of essential amino acids to TH abnormalities. We believe that the knowledge of these dependencies could improve the results of nutritional interventions in thyroid axis disorders and enhance the efficiency of animal breeding.

Vitamin D has a promising role in multiple sclerosis (MS) management, and it has been found to be beneficial for patients’ mental health, which is reduced in MS patients. The aim of the present study was to conduct a systematic review of the literature to assess the influence of vitamin D supplementation on mental health in MS patients. The systematic review was registered in the PROSPERO database (CRD42020155779) and it was conducted on the basis of the PRISMA guidelines. The search procedure was conducted using PubMed and Web of Science databases and it included studies published up until September 2021. Six studies were included in the systematic review. The risk of bias was analyzed using the Newcastle–Ottawa Scale (NOS). Within the included studies, there were two studies randomized against placebo and four other prospective studies. The studies presented vitamin D interventions randomized against placebo or not randomized, while supplementation was applied for various durations—from 4 weeks to 12 months, or the studies compared patients who applied vitamin D supplementation and those who did not apply it and verified the effect of the supplementation after a number of years. The mental health outcomes that were assessed included quality of life, depression/depressive symptoms, and fatigue as an additional element. The majority of studies supported the positive influence of vitamin D on the mental health of MS patients, including the study characterized as having the highest quality (randomized against placebo with the highest NOS score). All the studies that assessed the quality of life indicated the positive influence of vitamin D while the studies that did not find a positive influence of vitamin D were conducted for depression/depressive symptoms. In spite of the fact that only a small number of studies have been conducted so far, and only two studies were randomized against a placebo, some conclusions may be formulated. The systematic review allowed us to conclude that there may be a positive effect of vitamin D supplementation in MS patients, which was stated in all of the studies analyzing quality of life, as well as in one study analyzing depressive symptoms. Considering that vitamin D deficiency is common in MS patients, and the potential positive influence of supplementation on the quality of life, supplementation should be applied at least in doses that cover the recommended intake.

Vitamin D is considered to be a crucial factor that influences symptoms of depression, negative emotions, and quality of life, but to date, no systematic review has been conducted with regard to its effect on other domains of mental health. The aim of the study was to evaluate the influence of vitamin D supplementation on mental health in healthy adults. The systematic review was registered in the PROSPERO database (CRD42020155779) and performed according to the PRISMA guidelines. The literature search was conducted in PubMed and Web of Science databases and included intervention studies published until October 2019. The human studies were included if the supplementation regimen involved the administration of a specified dosage of vitamin D to an adult sample. A total of 7613 records were screened and assessed independently by two researchers, based on their title, abstract, and full text sequentially. Finally, 14 studies were included, and their risk of bias was assessed using the Newcastle–Ottawa Scale (NOS). The studies were included if they presented the results of various doses of vitamin D, compared the supplementation results with the placebo effect, compared the outcome with no supplementation, or observed effect of specific dose applied. The assessed mental health outcomes mainly included depressive symptoms, or depression, well-being, quality of life, mood, general mental component, and anxiety, but single studies also included other parameters such as distress, impression of improvement, and fear of falling and flourishing. The results of the majority of studies did not confirm a positive influence of vitamin D supplementation. None of the high-quality studies (assessed using NOS), which evaluated outcomes other than depression, supported the hypothesis that vitamin D supplementation effectively ameliorates mental health issues, while they present conflicting evidence for depression. Some studies indicated that supplementation should be combined with physical activity to provide effective results, and that supplementation is less effective than vitamin D supply from food sources. The included studies were conducted in diverse populations and followed various doses and intervals of administration, so the results may be incomparable, which should be considered as a limitation. The conducted systematic review did not provide strong evidence for a positive effect of vitamin D supplementation on mental health in healthy adults.

Inflammatory bowel diseases (IBDs) and irritable bowel syndrome (IBS) are associated with decreased quality of life and mental health problems. Among various approaches to supportive therapy that aims to improve mental health in affected individuals, vitamin D supplementation is considered to be an effective method which may also be beneficial in alleviating the symptoms during the course of IBDs and IBS. The aim of the present study was to conduct a systematic review of the literature presenting the data regarding the influence of vitamin D supplementation on mental health in adults with inflammatory and functional bowel diseases, including IBDs and IBS. This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (Registration number CRD42020155779). A systematic search of the PubMed and Web of Science databases was performed, and the intervention studies published until September 2021 were included. The human studies eligible to be included in the review should have described any intervention involving vitamin D as a supplement in a group of adult patients suffering from IBDs and/or IBS and should have assessed any component of mental health, but studies presenting the effects of combined supplementation of multiple nutrients were excluded. After eliminating the duplicates, a total of 8514 records were screened and assessed independently by two researchers. Further evaluation was carried out on the basis of title, abstract, and full text. Finally, 10 studies (four for IBDs and six for IBS) were selected for the current systematic review, and their quality was assessed using the Newcastle–Ottawa Scale (NOS). The studies analyzed the influence of various doses of vitamin D on bowel diseases, compared the results of vitamin D supplementation with placebo, or administered specific doses of vitamin D to obtain the required level in the blood. Supplementation was performed for at least 6 weeks. The analyzed mental health outcomes mainly included disease-specific quality of life/quality of life, anxiety, and depression. The majority of studies (including high-quality ones) confirmed the positive effect of vitamin D supplementation on the mental health of IBD and IBS patients, which was proven by all research works evaluating anxiety and depression and by the majority of research works evaluating quality of life. Although the studies followed different dosage regimens and supplementation protocols, the positive influence of vitamin D on mental health was found to be consistent. The number of studies on patients suffering from ulcerative colitis and the availability of trials randomized against the placebo group was low in the current review, which is considered to be a limitation of the present study and could also reflect the final outcome of the analysis. The conducted systematic review established the positive effect of vitamin D supplementation on the mental health of IBD and IBS patients, but this result requires further investigation, particularly in relation to other mental health outcomes.

Vitamin D is a nutrient potentially beneficial in the treatment of depression. The study aimed to carry out a systematic review of the studies assessing the influence of vitamin D supplementation on depression within Randomized Controlled Trials (RCTs). The systematic review was prepared on the basis of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42020155779). The peer-reviewed studies available within PubMed or Web of Science databases until September 2021 were taken into account. The number of screened records was 8514, and 8 records were included. Two independent researchers conducted screening, including, reporting, and risk of bias assessment using the revised Cochrane risk-of-bias tool for randomized trials. The included studies presented a population of patients with major depressive disorders or general depression, as well as bipolar depression or postpartum depression. The majority of included studies were conducted for 8 weeks or 12 weeks, while one study was conducted for 6 months. Within the large number of included studies, a daily dose of 1500 IU, 1600 IU, or 2800 IU was applied, while within some studies, a vitamin D dose of 50,000 IU was applied weekly or biweekly. Among applied psychological measures of depression, there were various tools. In spite of the fact that the majority of included studies (five studies) supported the positive effect of vitamin D supplementation for the psychological measure of depression, for three studies the positive influence was not supported. A medium risk of bias was indicated for six studies, while a high risk of bias was defined for only two studies, due to deviations from the intended interventions and in measurement of the outcome, as well as for one study, also arising from the randomization process and due to missing outcome data. Based on conducted assessment, it should be emphasized that there are only four studies supporting the positive influence of vitamin D supplementation for the psychological measure of depression of the medium risk of bias, while two studies of a medium risk of bias did not support it. Taking this into account, the conducted systematic review is not a strong confirmation of the effectiveness of vitamin D supplementation in the treatment of depression.

Diabetes is associated with a number of mental health consequences, including enhanced risk of depression and anxiety, as well as decreased quality of life, and vitamin D deficiency is considered to be one of the factors that influence these outcomes in diabetic patients. The aim of the present study was to conduct a systematic review of the literature presenting the data regarding the influence of vitamin D supplementation on mental health in diabetic adults. This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (Registration number CRD42020155779). A systematic search of the PubMed and Web of Science databases was performed, and the intervention studies published until September 2021 were included in the review. The human studies were included if an adult sample of diabetic individuals received vitamin D supplementation during the intervention and its effect on any mental health aspect was assessed, but studies presenting the influence of combined supplementation of multiple nutrients were excluded. After removing duplicate records, a total of 8,514 publications were screened and assessed independently by two researchers, based on their title, abstract, and full text. Finally, six studies were included in the current systematic review, and the risk of bias was evaluated using the Newcastle–Ottawa Scale (NOS). The included studies analyzed the influence of a specific dose of vitamin D, or different doses of vitamin D, or compared the results of supplementation with a specific dose of vitamin D against the placebo group. The supplementation was performed for at least 12 weeks. The mental health outcomes analyzed in these studies included health-related quality of life, depression, anxiety, stress, and general mental health status of adult diabetic patients. The results of the majority of the studies confirmed the positive influence of vitamin D supplementation on the mental health of diabetic individuals. Those studies that analyzed the influence of vitamin D supplementation on depression and anxiety established the beneficial effect of the vitamin. In some studies, the influence of vitamin D supplementation on the health-related quality of life was not considered unless combined with mindfulness training. However, it must be emphasized that different dosage regimens and intervention periods were followed in the reviewed studies, and only a small number of studies were randomized against placebo, which should be considered as a limitation of the present study. The findings of the conducted systematic review demonstrated the positive influence of vitamin D supplementation on the mental health of diabetic patients, which was proved for anxiety and depression, but in the case of health-related quality of life, the positive effect was observed only when the intervention included mindfulness training. These outcomes suggest that supplementation should be recommended to improve the vitamin D status and the mental health of patients in this group.