Background

Inconsistencies exist with regard to influence of vitamin D supplementation on IGF-1 levels. The inconsistencies could be attributed to several factors, such as dosage and duration of intervention, among others. To address these inconsistencies, this study was conducted to determine the impact of vitamin D supplementation on IGF-1 levels through a systematic review and meta-analysis of randomized controlled trials (RCTs).

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.

中文翻译：

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补充维生素D对人体IGF-1水平的影响：系统评价和荟萃分析。

背景

补充维生素D对IGF-1水平的影响存在矛盾。不一致可以归因于若干因素，例如干预的剂量和持续时间等。为了解决这些矛盾，本研究旨在通过对随机对照试验（RCT）进行系统回顾和荟萃分析，确定补充维生素D对IGF-1水平的影响。

方法

在PubMed / MEDLINE，Web of Science，SCOPUS和Embase中对RCT进行了全面的系统搜索，调查了从开始到2019年6月维生素D摄入量对循环IGF-1水平的影响。95加权均数差（WMD）将％CI用于估计组合效应大小。进行亚组分析以指定研究之间的异质性来源。

结果

八项研究的汇总结果表明，补充维生素D后，IGF-1总体上没有显着增加（WMD：4 ng / ml，95％CI：-4至11）。但是，在研究之间观察到了很大程度的异质性（I ² = 66％）。亚组分析显示，与<1000 IU /天（WMD：-1 ng / ml）的维生素D剂量相比，≤1000IU /天（WMD：10 ng / ml）的维生素D剂量显着增加了IGF-1。此外，与<12周（WMD：-3 ng / ml）的干预时间相比，≤12周（WMD：11 ng / ml）的干预时间显着增加了IGF-1。在流行病学队列研究中，与第二类饮食中维生素D摄入量较少的人群相比，饮食中维生素D摄入量较高的60岁以下参与者的IGF-1水平明显较高。

结论

主要结果表明，补充维生素D后，IGF-1含量没有显着增加。此外，每天<1000 IU /天的维生素D剂量和<12周的干预时间可显着提高IGF-1水平。