METHODS: A comprehensive systematic search was carried out in PubMed/MEDLINE, Web of Science, SCOPUS and Embase for RCTs that investigated the impact of vitamin D intake on circulating IGF-1 levels from inception until June 2019. Weighted mean difference (WMD) with the 95 % CI were applied for estimating combined effect size. Subgroup analysis was performed to specify the source of heterogeneity among studies.
RESULTS: Pooled results from eight studies demonstrated an overall non-significant increase in IGF-1 following vitamin D supplementation (WMD: 4 ng/ml, 95 % CI: -4 to 11). However, a significant degree of heterogeneity among studies was observed (I2 = 66 %). The subgroup analyses showed that vitamin D dosage of ≤1000 IU/day (WMD: 10 ng/ml) significantly increased IGF-1 compared to the vitamin D dosage of <1000 IU/day (WMD: -1 ng/ml). Moreover, intervention duration ≤12 weeks (WMD: 11 ng/ml) significantly increased IGF-1 compared to intervention duration <12 weeks (WMD: -3 ng/ml). In the epidemiological cohort study, participants under 60 years of age with a higher dietary vitamin D intake had significantly higher IGF-1 levels when compared to those with lower dietary vitamin D intake in second categories.
CONCLUSION: The main results indicate a non-significant increase in IGF-1 following vitamin D supplementation. Additionally, vitamin D dosages of <1000 IU/day and intervention durations of <12 weeks significantly raised IGF-1 levels.
METHODS: Scoping review methodology guided the synthesis of 272 publications on factors influencing physical activity. Bibliometric analysis examined publication trends, productivity, influential studies, content themes, and collaboration networks.
RESULTS: Since 2010, the United States has led a significant increase in research output. Highly cited articles identified physiological limitations and psychosocial determinants as key barriers and facilitators. Extensive focus was seen in clinical medicine and exercise science journals. Analysis revealed predominant attention to psychosocial factors, physiological responses, and applications in respiratory disease. Gaps remain regarding policy and environmental factors.
CONCLUSION: This review showed major advances in elucidating determinants while revealing the remaining needs to curb the pandemic of inactivity globally. Expanding international collaboration, contemporary theoretical models, and tailored mixed-methods approaches could promote progress through greater global participation. Addressing knowledge gaps across populations and disciplines should be a priority.